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  Subjects -> ENGINEERING (Total: 2515 journals)
    - CHEMICAL ENGINEERING (210 journals)
    - CIVIL ENGINEERING (219 journals)
    - ELECTRICAL ENGINEERING (120 journals)
    - ENGINEERING (1320 journals)
    - ENGINEERING MECHANICS AND MATERIALS (403 journals)
    - HYDRAULIC ENGINEERING (57 journals)
    - INDUSTRIAL ENGINEERING (84 journals)
    - MECHANICAL ENGINEERING (102 journals)

CIVIL ENGINEERING (219 journals)                  1 2 | Last

Showing 1 - 200 of 219 Journals sorted alphabetically
ACI Structural Journal     Full-text available via subscription   (Followers: 20)
Acta Polytechnica : Journal of Advanced Engineering     Open Access   (Followers: 3)
Acta Structilia : Journal for the Physical and Development Sciences     Open Access   (Followers: 3)
Advances in Civil Engineering     Open Access   (Followers: 43)
Advances in Structural Engineering     Full-text available via subscription   (Followers: 34)
Agregat     Open Access   (Followers: 1)
Ambiente Construído     Open Access   (Followers: 1)
American Journal of Civil Engineering and Architecture     Open Access   (Followers: 36)
Architectural Engineering     Open Access   (Followers: 5)
Architecture and Engineering     Open Access  
Architecture, Civil Engineering, Environment     Open Access   (Followers: 1)
Archives of Civil and Mechanical Engineering     Full-text available via subscription   (Followers: 3)
Archives of Civil Engineering     Open Access   (Followers: 13)
Archives of Hydro-Engineering and Environmental Mechanics     Open Access   (Followers: 2)
ATBU Journal of Environmental Technology     Open Access   (Followers: 4)
Australian Journal of Structural Engineering     Full-text available via subscription   (Followers: 7)
Baltic Journal of Road and Bridge Engineering     Open Access   (Followers: 1)
BER : Building and Construction : Full Survey     Full-text available via subscription   (Followers: 10)
BER : Building Contractors' Survey     Full-text available via subscription   (Followers: 2)
BER : Building Sub-Contractors' Survey     Full-text available via subscription   (Followers: 2)
BER : Survey of Business Conditions in Building and Construction : An Executive Summary     Full-text available via subscription   (Followers: 3)
Berkeley Planning Journal     Open Access   (Followers: 6)
Bioinspired Materials     Open Access   (Followers: 5)
Bridge Structures : Assessment, Design and Construction     Hybrid Journal   (Followers: 14)
Building & Management     Open Access   (Followers: 2)
Building and Environment     Hybrid Journal   (Followers: 16)
Building Women     Full-text available via subscription  
Built Environment Project and Asset Management     Hybrid Journal   (Followers: 15)
Bulletin of Pridniprovsk State Academy of Civil Engineering and Architecture     Open Access   (Followers: 6)
Canadian Journal of Civil Engineering     Hybrid Journal   (Followers: 14)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 6)
Case Studies in Nondestructive Testing and Evaluation     Open Access   (Followers: 11)
Case Studies in Structural Engineering     Open Access   (Followers: 10)
Cement and Concrete Composites     Hybrid Journal   (Followers: 20)
Challenge Journal of Concrete Research Letters     Open Access   (Followers: 3)
Challenge Journal of Structural Mechanics     Open Access   (Followers: 5)
Change Over Time     Full-text available via subscription   (Followers: 2)
Civil and Environmental Engineering     Open Access   (Followers: 8)
Civil and Environmental Engineering Reports     Open Access   (Followers: 8)
Civil and Environmental Research     Open Access   (Followers: 19)
Civil Engineering = Siviele Ingenieurswese     Full-text available via subscription   (Followers: 4)
Civil Engineering and Architecture     Open Access   (Followers: 24)
Civil Engineering and Environmental Systems     Hybrid Journal   (Followers: 3)
Civil Engineering and Technology     Open Access   (Followers: 13)
Civil Engineering Dimension     Open Access   (Followers: 12)
Civil Engineering Infrastructures Journal     Open Access   (Followers: 1)
Cohesion and Structure     Full-text available via subscription   (Followers: 2)
Composite Structures     Hybrid Journal   (Followers: 291)
Computer-aided Civil and Infrastructure Engineering     Hybrid Journal   (Followers: 11)
Computers & Structures     Hybrid Journal   (Followers: 37)
Concrete Research Letters     Open Access   (Followers: 7)
Construction Economics and Building     Open Access   (Followers: 4)
Construction Engineering     Open Access   (Followers: 11)
Construction Management and Economics     Hybrid Journal   (Followers: 21)
Constructive Approximation     Hybrid Journal  
Construindo     Open Access  
Curved and Layered Structures     Open Access   (Followers: 3)
DFI Journal : The Journal of the Deep Foundations Institute     Hybrid Journal   (Followers: 1)
Earthquake Engineering and Structural Dynamics     Hybrid Journal   (Followers: 17)
Enfoque UTE     Open Access   (Followers: 4)
Engineering Project Organization Journal     Hybrid Journal   (Followers: 7)
Engineering Structures     Hybrid Journal   (Followers: 13)
Engineering Structures and Technologies     Open Access   (Followers: 3)
Engineering, Construction and Architectural Management     Hybrid Journal   (Followers: 10)
Environmental Geotechnics     Hybrid Journal   (Followers: 5)
European Journal of Environmental and Civil Engineering     Hybrid Journal   (Followers: 10)
Fatigue & Fracture of Engineering Materials and Structures     Hybrid Journal   (Followers: 19)
Frontiers in Built Environment     Open Access   (Followers: 1)
Frontiers of Structural and Civil Engineering     Hybrid Journal   (Followers: 6)
Gaceta Técnica     Open Access  
Geomaterials     Open Access   (Followers: 3)
Geosystem Engineering     Hybrid Journal   (Followers: 2)
Geotechnik     Hybrid Journal   (Followers: 4)
Géotechnique Letters     Hybrid Journal   (Followers: 8)
GISAP : Technical Sciences, Construction and Architecture     Open Access  
HBRC Journal     Open Access   (Followers: 2)
Hormigón y Acero     Full-text available via subscription  
HVAC&R Research     Hybrid Journal  
Indonesian Journal of Urban and Environmental Technology     Open Access  
Indoor and Built Environment     Hybrid Journal   (Followers: 3)
Infrastructure Asset Management     Hybrid Journal   (Followers: 3)
Infrastructures     Open Access  
Ingenio Magno     Open Access   (Followers: 1)
Insight - Non-Destructive Testing and Condition Monitoring     Full-text available via subscription   (Followers: 36)
International Journal for Service Learning in Engineering     Open Access  
International Journal of 3-D Information Modeling     Full-text available via subscription   (Followers: 3)
International Journal of Advanced Structural Engineering     Open Access   (Followers: 17)
International Journal of Civil, Mechanical and Energy Science     Open Access   (Followers: 2)
International Journal of Concrete Structures and Materials     Open Access   (Followers: 15)
International Journal of Condition Monitoring     Full-text available via subscription   (Followers: 2)
International Journal of Construction Engineering and Management     Open Access   (Followers: 10)
International Journal of Engineering and Geosciences     Open Access  
International Journal of Geo-Engineering     Open Access   (Followers: 3)
International Journal of Geosynthetics and Ground Engineering     Full-text available via subscription   (Followers: 4)
International Journal of Masonry Research and Innovation     Hybrid Journal   (Followers: 1)
International Journal of Pavement Research and Technology     Open Access   (Followers: 6)
International Journal of Protective Structures     Hybrid Journal   (Followers: 6)
International Journal of Steel Structures     Hybrid Journal   (Followers: 2)
International Journal of Structural Engineering     Hybrid Journal   (Followers: 9)
International Journal of Structural Integrity     Hybrid Journal   (Followers: 2)
International Journal of Structural Stability and Dynamics     Hybrid Journal   (Followers: 7)
International Journal of Sustainable Built Environment     Open Access   (Followers: 5)
International Journal of Sustainable Construction Engineering and Technology     Open Access   (Followers: 8)
International Journal on Pavement Engineering & Asphalt Technology     Open Access   (Followers: 7)
International Journal Sustainable Construction & Design     Open Access   (Followers: 2)
Journal of Applied Research in Water and Wastewater     Open Access   (Followers: 1)
Journal of Bridge Engineering     Full-text available via subscription   (Followers: 13)
Journal of Building Engineering     Hybrid Journal   (Followers: 2)
Journal of Building Materials and Structures     Open Access   (Followers: 2)
Journal of Building Performance Simulation     Hybrid Journal   (Followers: 6)
Journal of Civil Engineering     Open Access   (Followers: 1)
Journal of Civil Engineering and Construction Technology     Open Access   (Followers: 16)
Journal of Civil Engineering and Management     Open Access   (Followers: 7)
Journal of Civil Engineering and Science     Open Access   (Followers: 10)
Journal of Civil Engineering Research     Open Access   (Followers: 8)
Journal of Civil Engineering, Science and Technology     Open Access   (Followers: 1)
Journal of Civil Society     Hybrid Journal   (Followers: 5)
Journal of Civil Structural Health Monitoring     Hybrid Journal   (Followers: 4)
Journal of Composites     Open Access   (Followers: 79)
Journal of Composites for Construction     Full-text available via subscription   (Followers: 13)
Journal of Computing in Civil Engineering     Full-text available via subscription   (Followers: 23)
Journal of Construction Engineering     Open Access   (Followers: 9)
Journal of Construction Engineering and Management     Full-text available via subscription   (Followers: 18)
Journal of Construction Engineering, Technology & Management     Full-text available via subscription   (Followers: 4)
Journal of Constructional Steel Research     Hybrid Journal   (Followers: 6)
Journal of Earth Sciences and Geotechnical Engineering     Open Access   (Followers: 4)
Journal of Fluids and Structures     Hybrid Journal   (Followers: 6)
Journal of Frontiers in Construction Engineering     Open Access   (Followers: 2)
Journal of Green Building     Full-text available via subscription   (Followers: 10)
Journal of Highway and Transportation Research and Development (English Edition)     Full-text available via subscription   (Followers: 14)
Journal of Infrastructure Systems     Full-text available via subscription   (Followers: 19)
Journal of Legal Affairs and Dispute Resolution in Engineering and Construction     Full-text available via subscription   (Followers: 5)
Journal of Marine Science and Engineering     Open Access   (Followers: 1)
Journal of Materials and Engineering Structures     Open Access   (Followers: 6)
Journal of Materials in Civil Engineering     Full-text available via subscription   (Followers: 8)
Journal of Nondestructive Evaluation     Hybrid Journal   (Followers: 9)
Journal of Offshore Structure and Technology     Full-text available via subscription  
Journal of Performance of Constructed Facilities     Full-text available via subscription   (Followers: 3)
Journal of Pipeline Systems Engineering and Practice     Full-text available via subscription   (Followers: 6)
Journal of Rehabilitation in Civil Engineering     Open Access   (Followers: 4)
Journal of Road and Traffic Engineering     Open Access  
Journal of Solid Waste Technology and Management     Full-text available via subscription   (Followers: 1)
Journal of Structural Engineering     Full-text available via subscription   (Followers: 36)
Journal of Structural Fire Engineering     Full-text available via subscription   (Followers: 6)
Journal of Structural Mechanics     Open Access   (Followers: 1)
Journal of Structures     Open Access   (Followers: 4)
Journal of Sustainable Architecture and Civil Engineering     Open Access   (Followers: 4)
Journal of Sustainable Design and Applied Research in Innovative Engineering of the Built Environment     Open Access   (Followers: 1)
Journal of the Civil Engineering Forum     Open Access   (Followers: 2)
Journal of the South African Institution of Civil Engineering     Open Access   (Followers: 2)
Journal of Water and Environmental Nanotechnology     Open Access  
Journal of Water and Wastewater / Ab va Fazilab     Open Access  
Jurnal Spektran     Open Access   (Followers: 1)
Jurnal Teknik Sipil     Open Access  
Jurnal Teknik Sipil dan Perencanaan     Open Access   (Followers: 1)
Konstruksia     Open Access  
KSCE Journal of Civil Engineering     Hybrid Journal   (Followers: 2)
Latin American Journal of Solids and Structures     Open Access   (Followers: 4)
Lithosphere     Open Access  
Materiales de Construcción     Open Access   (Followers: 1)
Mathematical Modelling in Civil Engineering     Open Access   (Followers: 5)
Media Komunikasi Teknik Sipil     Open Access  
Media Teknik Sipil     Open Access  
Mokslas – Lietuvos ateitis / Science – Future of Lithuania     Open Access  
Nondestructive Testing And Evaluation     Hybrid Journal   (Followers: 15)
npj Materials Degradation     Open Access  
Obras y Proyectos     Open Access   (Followers: 1)
Open Journal of Civil Engineering     Open Access   (Followers: 9)
Periodica Polytechnica Civil Engineering     Open Access  
Photonics and Nanostructures - Fundamentals and Applications     Hybrid Journal   (Followers: 4)
Practice Periodical on Structural Design and Construction     Full-text available via subscription   (Followers: 3)
Proceedings of the Institution of Civil Engineers - Bridge Engineering     Hybrid Journal   (Followers: 8)
Proceedings of the Institution of Civil Engineers - Civil Engineering     Hybrid Journal   (Followers: 14)
Proceedings of the Institution of Civil Engineers - Management, Procurement and Law     Hybrid Journal   (Followers: 10)
Proceedings of the Institution of Civil Engineers - Municipal Engineer     Hybrid Journal   (Followers: 2)
Proceedings of the Institution of Civil Engineers - Structures and Buildings     Hybrid Journal   (Followers: 4)
Promet : Traffic &Transportation     Open Access  
Random Structures and Algorithms     Hybrid Journal   (Followers: 5)
Recent Trends In Civil Engineering & Technology     Full-text available via subscription   (Followers: 5)
REDER : Revista de Estudios Latinoamericanos sobre Reducción del Riesgo de Desastres     Open Access  
Research in Nondestructive Evaluation     Hybrid Journal   (Followers: 6)
Resilience     Open Access   (Followers: 1)
Revista de Investigación     Open Access  
Revista IBRACON de Estruturas e Materiais     Open Access   (Followers: 1)
Revista Sul-Americana de Engenharia Estrutural     Open Access  
Road Materials and Pavement Design     Hybrid Journal   (Followers: 11)
Russian Journal of Nondestructive Testing     Hybrid Journal   (Followers: 5)
Science and Engineering of Composite Materials     Hybrid Journal   (Followers: 61)
Selected Scientific Papers - Journal of Civil Engineering     Open Access   (Followers: 3)
Slovak Journal of Civil Engineering     Open Access   (Followers: 2)
Soils and foundations     Full-text available via subscription   (Followers: 5)
Steel Construction - Design and Research     Hybrid Journal   (Followers: 3)
Structural and Multidisciplinary Optimization     Hybrid Journal   (Followers: 11)
Structural Concrete     Hybrid Journal   (Followers: 11)
Structural Control and Health Monitoring     Hybrid Journal   (Followers: 8)
Structural Engineering International     Full-text available via subscription   (Followers: 11)
Structural Mechanics of Engineering Constructions and Buildings     Open Access   (Followers: 1)
Structural Safety     Hybrid Journal   (Followers: 6)
Structural Survey     Hybrid Journal  
Structure     Full-text available via subscription   (Followers: 24)

        1 2 | Last

Journal Cover
Composite Structures
Journal Prestige (SJR): 1.905
Citation Impact (citeScore): 5
Number of Followers: 291  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0263-8223
Published by Elsevier Homepage  [3157 journals]
  • Hydrothermal in-plane-shear strength of carbon fibre/benzoxazine laminates
           manufactured out-of-autoclave by liquid-resin-infusion
    • Abstract: Publication date: Available online 16 January 2019Source: Composite StructuresAuthor(s): A.J. Comer, D. Ray, G. Clancy, W.O. Obande, I. Rosca, P.T. McGrail, W.F. Stanley Benzoxazine’s have recently emerged as new candidate resins for elevated temperature structural applications in the aerospace sector offering attractive attributes including infusibility under vacuum, fire-smoke-toxicity performance and room temperature storage/transport. The main objective of this study is to evaluate the hydrothermal in-plane-shear (IPS) strength of carbon-fibre (CF) based laminates manufactured using two benzoxazine (BZ) resin systems (BZ9120 and BZ9130). CF/BZ9130 was evaluated at 160 °C in the wet condition and benchmarked against two commercially available bismaleimide (BMI) resin systems - traditionally considered for wet applications at 160 °C. CF/BZ9120 was evaluated at 120 °C (just below its Tg) in the dry and wet condition and benchmarked against CF/BZ9130. BMI’s remain the benchmark for IPS strength at 160 °C (wet) with 64% retention while BZ9130 only retained 48% of IPS strength at 160°C (wet) and also exhibited excessive elongation. CF/BZ9130 showed good retention at 120 °C (68 % wet) outperforming CF/BZ9120 (48 % wet). Positively, both BZ systems performed at least as well as the BMI’s under ambient conditions.
       
  • Large-scale deformation and damage detection of 3D printed continuous
           carbon fiber reinforced polymer-matrix composite structures
    • Abstract: Publication date: Available online 16 January 2019Source: Composite StructuresAuthor(s): Congcong Luan, Xinhua Yao, Chuck Zhang, Ben Wang, Jianzhong Fu For the efficient monitoring regional deformation and damage of continuous carbon fiber reinforced polymer-matrix composite structures, a dual-material three-dimensional printing process was developed, in which continuous carbon fiber tows were integrated within the polymer matrix to construct smart sensing grids. Strategies based on the electrical-mechanical behavior of continuous carbon fiber tow for locating loading position and recognizing deformation field distribution, as well as damage detection, have been presented. The loading location can be determined through the maximum fractional change in electrical resistance of continuous carbon fiber tows in the longitudinal and transverse direction. A model based on the electrical-mechanical behavior of carbon fiber tow has been developed to identify the deformation field distribution. Both micro-damage and macro-damage can be detected according to the dramatic change in the slope of fractional change in electrical resistance with the strain. The effectiveness of above methods has been verified through experiments.
       
  • Experimental observation of fatigue degradation in a composite wind
           turbine blade
    • Abstract: Publication date: Available online 16 January 2019Source: Composite StructuresAuthor(s): Xiao Chen This study reports experimental observation of structural degradation in a composite wind turbine blade subject to fatigue loading. The fatigue test is carried out according to the test standard for the blade certification. The changes of bending stiffnesses, natural frequencies and damping ratios due to fatigue are examined and discussed. The study provides the first of this kind observation on full-scale composite rotor blades in the literature.
       
  • Analysis of the possibility of non-destructive testing to detect defects
           in multi-layered composites reinforced fibers by optical IR thermography
    • Abstract: Publication date: Available online 16 January 2019Source: Composite StructuresAuthor(s): Monika Pracht, Waldemar Swiderski The paper analyses the possibilities and effectiveness of using infrared thermography with optical thermal excitation by reflection approach in the case of multilayer composites reinforced fibers. The advantages and limitations of this technique have been demonstrated via composites reinforced with three types of fibers: glass, aramid, and carbon. The most common defects in such structures are: delaminations, fiber cracks, matrix cracks, and separation of fibers from the matrix. The paper describes some results of the numerical simulations of defects detection using optical IR thermography with the emphasis made on the inspection of multi-layer composite materials. The simulations were conducted in order to determine the detection of defects depending on the depth of their location under the front surface of composite material as well as their geometrical dimensions.
       
  • Implementation of bending-active elements in kinematic form-active
           structures – Part II: Experimental verification
    • Abstract: Publication date: Available online 14 January 2019Source: Composite StructuresAuthor(s): Silke Puystiens, Maarten Van Craenenbroeck, Danny Van Hemelrijck, Wim Van Paepegem, Marijke Mollaert, Lars De Laet The integration of bending-active elements in kinematic form-active structures opens new perspectives for the development of transformable architectural applications, introducing new typologies and interesting structural concepts. Structures that combine the use of membrane materials and the concept of active bending are referred to as ‘textile hybrids’.The complex interaction between the bending-active boundary elements and the membrane, but also the inherent high flexibility of both the membrane material and the bending-active elements, however, complicate the structural behaviour of the studied transformable textile hybrid. Therefore, an experimental verification of the structure becomes crucial to validate the results obtained through the numerical analysis and to allow a full understanding of the structural behaviour.This paper discusses the experimental set-up and investigation of a representative case study and compares the experimental results to the numerically obtained values.
       
  • Three-dimensional micromechanical assessment of bio-inspired composites
           with non-uniformly dispersed inclusions
    • Abstract: Publication date: Available online 14 January 2019Source: Composite StructuresAuthor(s): Aram Bahmani, Geng Li, Thomas L. Willett, John Montesano Bio-inspired composites with hexagonal platelet and cylindrical inclusions were studied. A novel algorithm termed staggered hardcore algorithm (SHCA) was used to rapidly generate 3D periodic representative volume elements (RVE) for bio-inspired composites with staggered non-uniformly dispersed inclusions. The spatial dispersions of inclusions in these generated RVEs were assessed using autocorrelation analysis, demonstrating the effectiveness of the SHCA algorithm. Orthotropic elastic properties of two different bio-inspired composites were computed and compared with analytical models, namely modified shear-lag, Mori-Tanaka and Halpin-Tsai, as well as available experimental data from the literature. For lower inclusion volume fractions, the computed results correlated well with experimental data and the analytical results. However, for higher inclusion volume fractions and aspect ratios the analytical results diverged, particularly Mori-Tanaka and modified shear-lag models which was similarly reported in previous studies. The capabilities of the computational model were further demonstrated through a comparative study of orthotropic elastic constants for the cylindrical and hexagonal inclusion composites. The study revealed the necessity to use 3D micromechanical models with realistic inclusion dispersions for accurately assessing the response of high inclusion volume fraction bio-inspired composites.
       
  • Mesoscale modelling of damage in half-hole pin bearing composite laminate
           specimens
    • Abstract: Publication date: Available online 14 January 2019Source: Composite StructuresAuthor(s): Fujian Zhuang, Puhui Chen, Albertino Arteiro, Pedro P. Camanho This paper presents the development and validation of a mesoscale numerical model for predicting the bearing damage and failure of composite laminates reinforced by unidirectional fibers. Firstly, half-hole pin bearing tests were carried out on composite laminates with both quasi-isotropic and soft lay-ups, as well as in specimens with variations in ply thickness and stacking sequence, using multiple measurement and inspection tools for a comprehensive characterization of the damage mechanisms. Then, three dimensional (3D) finite element models with fiber-aligned mesh for composite plies and considering various frictional contacts were built to simulate the bearing tests using a commercial explicit solver. The embedded material model incorporated 3D phenomenological invariant-based failure criteria using in situ ply strengths, mechanism-based continuum damage models (longitudinal bi-linear damage model and transverse smeared crack model) for intralaminar damage, and the cohesive zone model for interlaminar damage. Finally, detailed analyses and comparisons of the experimental and numerical results were performed in both macroscopic mechanical behavior and mesoscale failure mechanisms, where a good correlation was observed. Sensitivity studies on the effect of the modelling parameters on the post-peak response prediction were also conducted, providing relevant guidelines to identify future research directions.
       
  • Carbon/polyamide 6 thermoplastic composite cylinders for deep sea
           applications
    • Abstract: Publication date: Available online 14 January 2019Source: Composite StructuresAuthor(s): Mael Arhant, Briançon Christophe, Burtin Christian, Peter Davies The composite materials used at sea are today nearly all based on thermoset resins (polyester, epoxy). However, there is an increasing number of thermoplastic matrix polymers available on the market (PP, PA, PPS, PEEK…), which offer possibilities for forming by local heating, attractive mechanical properties and the potential for end of life recycling. The aim of this study was to design, manufacture and test thermoplastic composite pressure vessels for 4500 meter depth, in order to establish a technical, economic and ecological assessment of the use of these materials to replace traditional composites underwater. First, finite element calculations have been carried out to optimize the stacking sequence with respect to the external pressure and buckling resistance. Thick thermoplastic cylinders were then manufactured and tested until implosion, their behaviour showed a good agreement with calculations. Overall, the results show that it is possible to use Carbon/Polyamide 6 (C/PA6) thermoplastic composite cylinders for deep sea applications, as implosion pressures higher than 600 bar (6000 meter depth) were achieved.
       
  • Multi-scale structural topology optimization of free-layer damping
           structures with damping composite materials
    • Abstract: Publication date: Available online 14 January 2019Source: Composite StructuresAuthor(s): Heng Zhang, Xiaohong Ding, Hao Li, Min Xiong Damping performance of the free-layer damping structure mainly depends on the damping material layout and its material physical properties. This paper proposes a concurrent topology optimization method for the design of the multi-scale free-layer damping structures with damping composite materials. In order to maximize the structural damping performance, the density-based topology optimization method is adopted to find the optimal layout on both macro and micro scales. For this coupled system, the macrostructure is composed of periodic damping composite materials, a stiff damping material which is designed for maintaining the structural stiffness and a soft damping material which is used for improving structural damping. The homogenized effective complex elastic matrix is obtained by considering the two damping materials layout in the microstructure. Mathematical model is established and sensitivity analysis is deduced. Several numerical examples are presented to demonstrate the effectiveness of the proposed multi-scale optimization method. In-depth discussions are given for the effects of the volume fraction of soft damping material in the micro scale on the design results. The results show that there is an optimal volume ratio of the stiff and soft damping material to make the structure reach optimal vibration performance due to the effective competition of soft and stiff characteristics of different damping materials. The optimal microstructure has relatively great loss moduli and high material loss factor, and it also presents a negative Poisson’s ratio. The structural vibration performance of the optimal multi-scale layer damping structure with damping composite materials is significantly improved.
       
  • Novel hybrid frp tubular columns with large deformation capacity: concept
           and behaviour
    • Abstract: Publication date: Available online 12 January 2019Source: Composite StructuresAuthor(s): Tao Yu, Hongchao Zhao, Ting Ren, Alex Remennikov Extensive studies have been conducted on the use of fibre-reinforced polymer (FRP) as a confining material in hybrid tubular columns for civil construction, where the design of columns is often controlled by the stiffness and/or strength requirements. By contrast, the capacity of sustaining large deformation without losing structural integrity can be critical in some applications such as the standing supports for underground mines. This paper presents the conceptual development of a novel column form with large deformation capacity. The novel column consists of an outer FRP tube, and an infill made of coarse lumps/aggregates, which can be from coal rejects or other waste/recycled materials, as well as calcium sulfoaluminate (CSA)-based cementitious material with high water content. In addition to its large deformation capacity, the new column allows the extensive, direct and easy use of waste materials and eliminates the need for mixing concrete on site or transporting commercial concrete. This paper also presents the results from a series of compression tests on the new columns as well as two similar column forms. These tests demonstrate the very large deformation capacity of the new column and show that an existing stress-strain model for FRP-confined normal concrete can be used to provide reasonable predictions of the behaviour of the confined infill material in the new column. The potential applications of the new column and the needs for future research are also discussed.
       
  • Static and Dynamic Characterization of Agglomerated Cork and Related
           Sandwich Structures
    • Abstract: Publication date: Available online 11 January 2019Source: Composite StructuresAuthor(s): F. Sarasini, J. Tirillò, L. Lampani, M. Sasso, E. Mancini, C. Burgstaller, A. Calzolari The aim of this experimental investigation is to assess the response to low velocity impacts of green sandwich structures made of agglomerated cork encapsulated between two thin flax/epoxy face sheets. Three different cork densities were considered to assess their role on the response to impulsive loading, both in low and high strain rate conditions by Split Hopkinson Pressure Bar (from 90 to 238 1/s). The performance of these structures has been compared to that obtained with similar specimens using a traditional synthetic foam core. Despite the lower quasi-static mechanical properties of high-density cork (modulus and collapse stress of 117.65±4.04 MPa and 4.29±0.06 MPa, respectively), the cork-based structures exhibited a higher perforation threshold (94.41±2.37 J) than synthetic foam-based sandwiches (79.71±2.24 J) for impacts at room temperature. Finally, the material performance was evaluated under different temperatures, namely -40 °C and +80 °C, where perforation thresholds were found to be higher for cork-based structures (113.98±6.04 J and 101.05±2.42 J) compared to synthetic foam-based sandwiches (94.39±2.20 J and 77.64±1.70 J). The results show that the distinctive deformation mechanisms of cork allow to tailor the response to impulsive loading with a tunable damage extension through-the-thickness, despite a pronounced temperature dependent behaviour compared to synthetic foam.
       
  • An Automatic Finite Element Modelling for Deformation Analysis of
           Composite Structures
    • Abstract: Publication date: Available online 11 January 2019Source: Composite StructuresAuthor(s): Hao Yang, Xiangyang Xu, Ingo Neumann Terrestrial laser scanning is extensively adopted in the area of high-precision monitoring and three-dimensional measurement. Architectural structures today are increasingly complex and health monitoring plays an important role in guaranteeing their safety. Therefore, how reliability deformation monitoring can be improved is one of the key problems in the field of engineering. This paper combines the three-dimensional laser scanning technology and finite element method (FEM) to investigate the deformation mechanism of arched structures. Within this paper, we simulated arched structures using the FEM, which is consistent with the result of terrestrial laser scanner (TLS) measurement. We aimed at constructing an intelligent and efficient FEM model which can be extensively applied in the monitoring of many constructs, such as bridges and ancient architecture. The focus in this research lies mainly on deformation analysis, which is based on FEM model simulation with the calibration of TLS measurement.
       
  • Enhancing the bearing strength of woven carbon fibre thermoplastic
           composites through Additive Manufacturing
    • Abstract: Publication date: Available online 11 January 2019Source: Composite StructuresAuthor(s): Andrew N. Dickson, Denis P. Dowling This paper examines a novel additive manufacturing (AM) technique for the fabrication of woven multilaminate composites. The printing studies were carried out using nylon coated carbon fibre Tow in the form of a filament. This pathing technique allows for a woven structure to be integrated with features (such as notches) previously only possible through destructive machining processes. In order to evaluate the performance of these printed composites, bearing response studies were carried out. 6 mm holes were routed into a multilaminate woven composite structure, the resulting part’s mechanical performance was then tested and compared with specimens which had been drilled post printing. Specimen were comprised of 9 woven laminates stacked to form a 3.1 mm thick standardised test coupon for single and double shear testing (ASTM D5961). Current industry standard machining techniques result in fibre discontinuity and damage, this results in suboptimal mechanical performance of composite components. These new ‘Tailor Woven’ specimens achieved single shear bearing strengths of up to 214 MPa and double shear bearing strengths of up to 276 MPa. These values represent an increase of 29% and 63% respectively compared with equivalent composites in which the hole had been drilled.
       
  • A Real-time Electromechanical Impedance-based Active Monitoring for
           Composite Patch Bonded Repair Structure
    • Abstract: Publication date: Available online 11 January 2019Source: Composite StructuresAuthor(s): Jianjian Zhu, Yishou Wang, Xinlin Qing With the increase of serving time, the metallic primary structures are extremely likely to risk structural failures due to aging and external loads. Composite patch bonded repair offers an effective technique for recovering the ultimate load-bearing capability of the structure. Disbond between the composite patch and the substrate structure is a typical failure mode that severely reduces the structural stiffness and strength of repair region. In this paper, a combining active monitoring scheme is proposed based on electromechanical impedance (EMI) and coupling constitutive equations. Two statistical damage indices (DIs), root mean square deviation (RMSD) and mean absolute percentage deviation (MAPD), are adopted for locating the disbond and evaluating its severity based on extracted signatures. Experiments on the repair patch with a 3×3 sensors array are performed to monitor the disbond on the interface between the repair patch and substrate. Experimental results show that both disbond locations and severities on the bondline can be monitored efficaciously by the proposed active monitoring scheme.
       
  • A nonlinear couple stress model for periodic sandwich beams
    • Abstract: Publication date: Available online 10 January 2019Source: Composite StructuresAuthor(s): Bruno Reinaldo Goncalves, Anssi T. Karttunen, Jani Romanoff A geometrically nonlinear model for periodic sandwich structures based on the modified couple stress Timoshenko beam theory with von Kármán kinematics is proposed. Constitutive relations for the couple stress beam are derived assuming an antiplane core and then extended for a generic periodic cell. A micromechanical approach based on the structural analysis of a unit cell is proposed and utilized to obtain the stiffness properties of selected periodic sandwich beams. Then, a localization scheme to predict the stress distribution over the faces of the selected beams is defined. The present model is shown to be equivalent to the thick-face sandwich theory for a linear elastic antiplane core cell. Numerical studies validate the present model against three-dimensional finite element models and the thick-face sandwich theory, and compare it with the conventional Timoshenko and couple stress Euler-Bernoulli beam theories. The present model is shown to predict deflections, stresses and buckling loads with good accuracy for different periodic cell setups. The model is able to describe elastic size effects in shear-flexible sandwich beams and the core stiffness influence on membrane and bending stress resultants.
       
  • Stability and strength analysis of thin-walled GLARE composite profiles
           subjected to axial loading
    • Abstract: Publication date: Available online 10 January 2019Source: Composite StructuresAuthor(s): D. Banat, R.J. Mania The subject of the paper is the stability and strength analysis of Fibre Metal Laminate thin-walled members subjected to axial loading. This study concerns specifically angle-ply multi-layered Glass Reinforced Aluminium (GLARE) composite type wherein the main focus is on the top-hat open cross-section profiles. Specimens were prepared by autoclave technique that provided a high-quality manufacturing. Symmetrical 3/2 lay-ups were analysed for which 7 stacking sequences were distinguished based on the fibres alignment in the composite layer. Composite specimens were axially compressed in laboratory tests by means of static testing unit that provided displacement control loading. The behaviour of thin-walled GLARE members was investigated with the main attention to post-buckling response together with various failure modes. First Ply Failure (FPF) analysis was carried out simultaneously by Tsai-Wu, Hashin and Puck failure criteria in order to detect a first failure occurrence. FEM analysis included also an attempt to estimate particular regions of laminate’s damage in post-buckling state. Application of various failure criteria allowed to track failure initiation and predict collapsed mode shapes of GLARE top-hat members that were found to be in a good agreement with experimental evidences.
       
  • Closed-form methodology for stress analysis of composite plates with
           cutouts and non-uniform lay-up
    • Abstract: Publication date: Available online 10 January 2019Source: Composite StructuresAuthor(s): D. Pastorino, A. Blázquez, B. López-Romano, F. París This study aims to develop a closed-form methodology for estimating the resultant forces in a finite composite plate, weakened by the presence of elliptical cutouts, under membrane loads. Following an innovative approach, the developed methodology can deal, in the presence of cutouts, with a non-uniform lay-up distribution in the plate. To this end, different laminate features, including the stacking sequence, thickness, and even local reinforcements, will be considered as variable inputs. The main motivation behind this research is to increase the range of applicability of the closed-form methodologies devoted to the structural analysis of composite plates with cutouts, with the purpose of using the present methodology in the first phases of component design.
       
  • Viscous Fluid Structure Interaction Response of Composite Hydrofoils
    • Abstract: Publication date: Available online 10 January 2019Source: Composite StructuresAuthor(s): Yingqian Liao, Nitin Garg, Joaquim R.R.A. Martins, Yin L. Young Composite materials are increasingly used in hydrodynamic lifting surfaces due to their higher specific strength and favorable fatigue properties. A set of parametric studies are performed to investigate the influence of fiber orientation on the vibration characteristics and load-dependent bend-twist coupled behavior of composite hydrofoils in viscous flow. A 3-D Reynolds-averaged Navier–Stokes (RANS) solver is coupled with a 3-D finite-element method (FEM) to predict the fluid-structure response of cantilevered composite hydrofoils made of unidirectional carbon fiber reinforced polymer (CFRP). Fiber orientation changes the modal characteristics of composite hydrofoils, as well as the hydroelastic response. The bending-up and nose-down material bend-twist coupling leads to lower hydrodynamic load coefficients with increasing flow speed, as well as delayed separation, stall, and static divergence. The opposite trend is observed when the fiber orientation results in a bending-up and nose-up material bend-twist coupling. Failure index contours show that the fiber orientation affects the location of failure. These parametric studies provide guidance for future design and optimization studies of composite hydrodynamic lifting surfaces.
       
  • Tensile behaviour of glass frcm systems with fabrics’ overlap:
           experimental results and numerical modeling
    • Abstract: Publication date: Available online 10 January 2019Source: Composite StructuresAuthor(s): Jacopo Donnini, Gianluca Chiappini, Giovanni Lancioni, Valeria Corinaldesi The use of Fabric Reinforced Cementitious Matrix (FRCM) systems to reinforce existing masonry and concrete structures is nowadays a well-established practice. The mechanical characterization of FRCM systems is of fundamental importance to define the correct parameters needed to design a strengthening intervention. However, some aspects regarding FRCM tensile behaviour need to be further investigated.The aim of this paper is to provide a detailed overview on the mechanical behaviour of FRCM specimens subjected to tensile tests. In this context, the effect of fabrics’ overlapping on the global behaviour of the system is extensively analyzed. Different sample’s configurations have been studied: one reinforced with a single layer of bidirectional glass fabric and three others with different fabrics’ overlap lengths, varying between 100 and 200 mm. Digital Image Correlation (DIC) has been also used to measure displacements in experimental testing.A phase-field model, that accounts for brittle fracture of cementitious matrix and fabric reinforcement and possible slippage at the fabric-to-matrix interface, has been developed. The variational formulation has been implemented in a finite element code to simulate the tensile behaviour of FRCM systems and the effects of using different fabrics’ overlap lengths.
       
  • Application of Continuum Decohesive Finite Element to Progressive Failure
           Analysis of Composite Materials
    • Abstract: Publication date: Available online 9 January 2019Source: Composite StructuresAuthor(s): Shiyao Lin, Nhung Nguyen, Anthony M. Waas The continuum decohesive finite element (CDFE) is a novel finite element technique combining continuum and cohesive crack modeling seamlessly. In CDFE, the transition from a continuum to non-continuum is modeled physically by introducing pairs of dummy nodes to account for the crack separations. A static condensation algorithm is applied to solve for and preserve the separations. In this paper, CDFE has firstly been applied to the modeling of transverse crack growth in a representative volume element (RVE) of composite materials. Microscopic cracks initiate separately and coalesce into a macroscopic transverse crack. In this case, mode I cracking is dominant and the maximum principal stress criterion is used for crack angles. The second problem set is the delamination toughness tests, including a double cantilever beam (DCB) test, an end notched flexure (ENF) test and mixed mode bending (MMB) tests of three mixed mode ratios. In these cases, the crack plane is well-defined and mode mixity is encountered. For better numerical stability, the CDFE inner-element discretization scheme is modified and a novel mixed mode cohesive formulation is implemented. Through analyses, the capability of CDFE to deal with general progressive failure problems of composite materials is shown.
       
  • Refined multi-phase-lags theory for photothermal waves of a gravitated
           semiconducting half-space
    • Abstract: Publication date: Available online 8 January 2019Source: Composite StructuresAuthor(s): Ashraf M. Zenkour A refined multi-phase-lags theory for thermoelastic photothermal response of half-space semiconducting medium is presented. The semiconducting medium is subjected to the internal heat source as well as a gravity effect. The photothermal wave propagation of a gravitated semiconducting half-space has been examined. A fourth equation for the plasma transport is added to the old thermoelastic partial differential equations. All coupled photo-thermoelastic equations have been resolved exactly due to the normal mode model. A harmonic wave solution is adopted to derive the main variables of the medium. The temperature, horizontal and vertical displacements, stresses, and carrier density have been obtained. A comparison is made to show the dependency of all field variables on the internal heat source and the inclusion of gravity. Most variables are very sensitive to the variation of the heat source and gravity factor. Results are tabulated to serve as benchmarks for future comparisons and additional results have been displayed to show the physical meaning of the phenomena.
       
  • Higher-order finite element models for the static linear and nonlinear
           behaviour of functionally graded material plate-shell structures
    • Abstract: Publication date: Available online 8 January 2019Source: Composite StructuresAuthor(s): José S. Moita, Victor Franco Correia, Cristóvão M. Mota Soares, José Herskovits In this work, finite element formulations based on higher order shear deformation theories are used for the nonlinear static analysis of Functionally Graded Material plate-shell type structures. Linear and geometric nonlinear behaviour of the plate-shell type structures are considered. For the nonlinear analysis, the incremental equilibrium path is obtained using the updated Lagrangian procedure and Newton-Raphson incremental-iterative method, incorporating the automatic arc-length method for the cases of snap-through occurrence. The finite element models are based on a non-conforming triangular flat plate/shell element with 3 nodes and 8 or 11 degrees of freedom per node. The solutions of some illustrative plate-shell examples are performed, and the results are presented and discussed with numerical alternative models.
       
  • Virtual calculation of the B-value allowables of notched composite
           laminates
    • Abstract: Publication date: 15 March 2019Source: Composite Structures, Volume 212Author(s): O. Vallmajó, I.R. Cózar, C. Furtado, R. Tavares, A. Arteiro, A. Turon, P.P. Camanho The design of composite structures relies on the accurate determination of design allowables, which are statistically based material parameters that take into account manufacturing, geometrical and microstructure variability. The accurate determination of these design parameters requires extensive experimental testing, which makes the certification process of a composite material extremely costly and time consuming. To increase the efficiency of the design process, there is the need to develop alternatives to the mostly experimental material characterization process, ideally based on accurate and quick modelling analysis combined with powerful statistical tools.In this work an analytical model to compute the notched strength of composite structures based on three ply-based material properties (elastic modulus, unnotched strength and R-curve) is combined with an uncertainty quantification and management (UQ&M) framework to compute the B-basis design allowables of notched configurations of CFRP laminates. The framework is validated with open-hole tension experimental results for the IM7/8552 material. Given the analytical nature of the developed framework and consequent computational efficiency, the UQ&M methodology is applied to the generation of design charts for notched geometries, whose generation would otherwise be impractical, using experimental test based methods.
       
  • Numerical modelling of bond shear stress slip behavior of CFRP/steel
           composites cured and tested at elevated temperature
    • Abstract: Publication date: 15 March 2019Source: Composite Structures, Volume 212Author(s): E.R.K. Chandrathilaka, J.C.P.H. Gamage, S. Fawzia This paper presents a numerical model developed to predict the bond characteristics of CFRP/steel composites cured under different curing conditions and their behaviour at elevated temperatures. The measured material properties and their degradation with the temperature exposure were considered. The predicted bond performance was in a good agreement with the test results. The strain variation in the CFRP sheet was used to develop the bond shear stress-slip variations. Parametric studies were also conducted to evaluate the effects of bond line parameters on the bond shear stress-slip relationship at elevated temperature. The results indicate that the maximum bond shear stress of the joint lies in the range between 25 MPa and 28 MPa at ambient conditions, irrespective of the curing type. A rapid decrease in the maximum bond shear stress appears with exposure to the elevated temperature. Maximum shear stress reaches 10 MPa when the bond line temperature exceeds 90 °C. The elevated temperature curing, exposed temperature during service and the bond thickness notably affects on the bond slip behavior.
       
  • An analytical model to predict stress fields around broken fibres and
           their effect on the longitudinal failure of hybrid composites
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Jose M. Guerrero, Rodrigo P. Tavares, Fermin Otero, Joan A. Mayugo, Josep Costa, Albert Turon, Pedro P. Camanho This paper presents an analytical model to predict the stress redistribution around broken fibres in hybrid polymer composites. The model is used under the framework of a progressive failure approach to study the load redistribution around breaks in hybrid composites. The outcomes of the model are validated by comparing it with a spring element model. Moreover, the approach is further used to study the tensile behaviour of different hybrid composites. The results obtained show that the load redistribution around breaks depends on the stiffness ratio between both fibres as well as the matrix behaviour considered and the hybrid volume fraction. Furthermore, the different material parameters have a large effect on the tensile behaviour, with an increase of ductility achieved if the failure process of the two fibres is gradual.
       
  • Quality assessment and damage detection in nanomodified adhesively-bonded
           composite joints using inkjet-printed interdigital sensors
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Dimitrios G. Bekas, Zahra Sharif-Khodaei, Dimitrios Baltzis, M.H. Ferri Aliabadi, Alkiviadis S. Paipetis In this work, the development of a planar interdigital capacitive sensor, directly onto the surface of a composite, for determining the initial quality of curing of bonded composite joints and assessing their long-term durability is presented. The sensor consisted of an interlocking comb-shaped array of silver electrodes and used to monitor the progress of cure of an adhesive resin and the subsequent damage state of the bond line in adhesively-bonded composite joints using impedance spectroscopy. The obtained results from the mechanical characterization indicated that the developed sensor did not affect the quality of the bondline while the added weight of the sensor is negligible. The curing process of the adhesive epoxy was successfully monitored while the ability of the sensor to assess the developed damage created by the mechanical loading was confirmed using transient infrared thermography.
       
  • Consistent 2D formulation of thermoelastic bending problems for FGM plates
    • Abstract: Publication date: Available online 8 January 2019Source: Composite StructuresAuthor(s): L. Sator, V. Sladek, J. Sladek In this paper, we present the development of completely 2D formulation for bending of functionally graded plates subjected to stationary thermal loading. Consistently with the assumptions made in plate bending theories, the temperature field in 3D domain is expanded into low order power-law series with respect to transversal coordinate and the original 3D formulation (governing equation and boundary conditions) is recast according to physical principles into 2D formulation. A unified formulation is developed using the assumptions of three plate bending theories such the Kirchhoff-Love theory for bending of thin plates (KLT) and the shear deformation plate theories of the 1st and 3rd order (FSDPT, TSDPT) valid for thick plates too. The derivation is performed with assuming the power-law gradation of material coefficients (such as the Young modulus, linear thermal expansion coefficient, and heat conduction coefficient) across the plate thickness. For variation of material coefficients and plate thickness within the mid-plane, arbitrary continuous function is allowed. In numerical simulations, the derived formulation is implemented numerically by using the strong formulation and mesh-free Moving Least Square-approximation. The original PDE with high order derivatives are decomposed into a system of 2nd order PDE.
       
  • Durability of composite assemblies under extreme conditions:
           Thermomechanical damage prediction of a double-lap bonded composite
           assembly subject to impact and high temperature
    • Abstract: Publication date: Available online 8 January 2019Source: Composite StructuresAuthor(s): Georgio Rizk, Roula Nahas, Khaled Khalil, Georges Challita, Vincent Legrand, Pascal Casari, Frédéric Jacquemin The objective of this study is to simulate and predict the thermomechanical damage of composite material assemblies subjected to impact load while in a high temperature environment. Three-dimensional models were developed for a glass-fiber reinforced vinyl ester double-lap bonded composite assembly subject to combined mechanical and high thermal loads. Both thermal and mechanical models were implemented in the finite element analysis software Abaqus, using sequential heat transfer and dynamic implicit simulations. The thermal model is customized to properly simulate the thermal behavior of composites and generate accurate results while the mechanical model uses the existing functions of Abaqus. For a double-lap composite assembly, thermomechanical failure is predicted in the adhesive zone, at the adherent/adhesive interface, as the adhesive deteriorates at the early stages of exposure. The adherent also deteriorates but at a slower rate. Furthermore, stress concentration is observed at the edges of the stress distribution along the adhesive length, while the average stress along the length decreases gradually as a function of the fire exposure time. The conducted simulations made it possible to predict the stress distribution field variation as a function of time in the double-lap bonded assembly under a combined thermal-impact load. This would serve as a valuable tool for composite structure designers in sizing bonded composite assemblies for their structural projects, as the specifications for certain structures impose a time of evacuation of the structure during a shock and triggering of a fire.
       
  • On the characterisation and modelling of high-performance para-aramid
           fabrics
    • Abstract: Publication date: Available online 8 January 2019Source: Composite StructuresAuthor(s): M.M. Moure, N. Feito, J. Aranda-Ruiz, J.A. Loya, M. Rodriguez-Millán In this work, seven different types of fabrics based on para-aramid yarns with different interlacing geometries and reinforcement polymer matrix have been characterised and compared from yarn level to weave level. Mechanical properties such as maximum stress, failure strain, and elastic modulus have been obtained from uniaxial tensile tests, while the inter-yarn friction coefficients (static and kinetic) have been obtained by a combination of single yarn pull-out tests and an analytical model. Results show that mechanical properties are quite similar at yarn level but different at fabric level. Thus, the geometry, orientation and section of the yarn play an important role in the mechanical properties of the fabric. As an application of these results, a mesoscopic three-dimensional numerical model has been developed, and simulations of ballistic impact test have been carried out validating the model with experimental tests.
       
  • Concurrent Design and Manufacture of a Thermoplastic Composite Stiffener
    • Abstract: Publication date: Available online 7 January 2019Source: Composite StructuresAuthor(s): Daniël Peeters, Gearóid Clancy, Vincenzo Oliveri, Ronan O’Higgins, David Jones, Paul M. Weaver Fibre reinforced composite materials are finding increasing application in aerospace structures due to their superior specific properties. Aerospace structures make widespread use of stiffening elements, such as stringers, for example in wingboxes and fuselage structures. Sizing of stiffeners to fulfil strength, stiffness and manufacturing considerations is a significant challenge. Herein, a novel manufacturing approach using winding in combination with laser-assisted tape placement is used to manufacture an omega-shaped stiffener made from carbon fibre thermoplastic material. This paper discusses the integrated approach taken by considering material choice, manufacturing constraints and structural design on the performance of a closed-section omega stiffener. The sizing is based on the buckling response of the wingbox, with manufacturing constraints taken into consideration. In the collapsible mould, a low-melt aluminium alloy is used as a spacer, which can be removed post-process by exposing the mould to the alloy melt temperature, which is below the glass transition temperature of the thermoplastic composite material. Manufacturing tests show that repeatable stiffeners of the appropriate dimensions are manufactured. Characterisation tests show that both the bond strength, measured using an interlaminar shear strength test, and the corner strength, assessed using a four-point bend test, are satisfactory.
       
  • A robust Bézier based solution for nonlinear vibration and post-buckling
           
    • Abstract: Publication date: Available online 6 January 2019Source: Composite StructuresAuthor(s): H. Kabir, M.M. Aghdam In the present study, an accurate Bézier based multi-step method is developed and implemented to find the nonlinear vibration and post-buckling configurations of Euler-Bernoulli composite beams reinforced with graphene nano-platelets (GnP). The GnP is assumed to be randomly and uniformly dispersed in the composite mix-proportion, with a random checkerboard configuration. Therefore, a probabilistic model together with an efficient simulation technique is proposed to find the effective moduli of a matrix reinforced GnP. It is worth noting that the presented micro-mechanics model found by the employed Monte-Carlo simulation matches exactly the experimental data and predicts the composite elastic constants more accurate than that found from other common methods, including the Halpin-Tsai theory. Also, for mathematical simplification, the composite beam in-plane inertia is neglected. The presented multi-step method is based on Burnstein polynomial basis functions while shows interesting potential to provide robust solutions for various initial and boundary value problems. It is found that adding a relatively low content of GnP would drastically increase the composite elastic constants, particularly in the transverse direction to fiber. In addition, the numerical results are compared with those provided by exact analytical solutions, where the stability of results suggests the effectiveness of the presented methodology.
       
  • A multi-scale model for studying failure mechanisms of composite blades
    • Abstract: Publication date: Available online 6 January 2019Source: Composite StructuresAuthor(s): Junjie Ye, Chenchen Chu, Heng Cai, Xiaonan Hou, Baoquan Shi, Shaohua Tian, Xuefeng Chen, Jianqiao Ye Composite structures have been widely used in wind turbine equipment for their high stiffness to mass ratio and high strength. A major concern in the use of composite materials is their susceptibility to various micro damage, such as fiber breakage and matrix crack, which will lead to macroscopic structural fracture. In this paper, a multi-scale modeling strategy is proposed to investigate failure mechanisms and damage evolution of composite blades with initial defects from microscopic damage (including fiber fractures and matrix cracks) to macroscopic fracture. At the microscopic scale, an isoparametric micromechanical model is developed to calculate microscopic stresses and simulate microscopic damage. At the laminar scale, the classic laminate theory is employed to evaluate the laminate stiffness. At the structural scale, a reverse modeling technology is proposed to accurately acquire structural dimensions of a wind turbine blade, and a macroscopic 3D model is implemented into ANSYS/LS-DYNA software. By comparing with the experimental data, it is demonstrated that the proposed multi-scale method is suitable to predict mechanical properties of complex composite structures effectively.
       
  • Static and dynamic effective thickness in five-layered glass plates
    • Abstract: Publication date: Available online 6 January 2019Source: Composite StructuresAuthor(s): M. López-Aenlle, F. Pelayo In the last years, the effective thickness concept has been used to calculate deflections, stresses and modal parameters in laminated glass beams and plates, which consists of using a monolithic element with equivalent bending properties to a laminated element, i.e. the thickness of the equivalent monolithic model is time and temperature dependent because the interlayers show a viscoelastic behavior. Multi-layered laminated glass panels are those with at least three monolithic glass layers and two viscoelastic interlayers which are commonly used in floors, roofs and other applications where a high level of security is required. In this paper, a static deflection effective stiffness for a laminated glass plate consisting of three glass layers and two polymeric interlayers is derived. This static effective thickness is then extended to the frequency domain using the correspondence principle. The models are validated by static experimental tests and operational modal tests carried out on a rectangular multi-layered laminated glass plate pinned supported at the four corners.
       
  • Performance of Externally Strengthened RC Beams with Side-Bonded CFRP
           Sheets
    • Abstract: Publication date: Available online 6 January 2019Source: Composite StructuresAuthor(s): A.S.D. Salama, R.A. Hawileh, J.A. Abdalla The conventional method of strengthening reinforced concrete (RC) beams in flexure is via bonding carbon-fiber reinforcement polymer (CFRP) laminates to the beam’s soffit. However, the beam’s soffit could be narrow or inaccessible for strengthening. To overcome such obstacles, this paper explores the feasibility of strengthening RC beams in flexure by side-bonded CFRP composite sheets. Accordingly, a total of nine RC beams have been cast, eight of which were strengthened in flexure with different configurations of bottom-bonded and side-bonded CFRP sheets, and tested under four-point bending till failure. The load-deflection response curves, failure modes, and ductility of the tested specimens were recorded and compared. Overall, it is observed that specimens strengthened with similar amount of reinforcement are comparable with percent increase in the flexural strength over the control beam ranged from 62-92% for bottom-bonded and 39.7-93.4% for side- bonded strengthened beams. In addition, an analytical model based on ACI 440.2R-08 guidelines is developed and the predicted flexural strength was in good agreement with experimental results with differences ranging between 2.4% to 6.8%. It is concluded that the proposed side-bonded strengthening scheme is a valid alternative to the bottom-bonded scheme of strengthening of RC beams in flexure.
       
  • Application of first-order shear deformation theory for the vibration
           analysis of functionally graded doubly-curved shells of revolution
    • Abstract: Publication date: Available online 6 January 2019Source: Composite StructuresAuthor(s): Haichao Li, Fuzhen Pang, Yuhui Li, Cong Gao A semi analytical method is employed to analyze free vibration behaviors of functionally graded (FG) doubly-curved shells of revolution subject to general boundary conditions. The analytical model is established on basis of multi-segment partitioning strategy and first-order shear deformation theory. The displacement functions are made up of the Jacobi polynomials along the axial direction and Fourier series along the circumferential direction. In order to obtain continuous conditions and satisfy general boundary conditions, the penalty method about spring technique is adopted. The solutions about free vibration behaviors of FG doubly-curved shells were obtained by approach of Rayleigh–Ritz. The convergence study and numerical verifications for FG doubly-curved shells with different boundary conditions, Jacobi parameters, spring parameters and truncation of permissible displacement functions are carried out. Through the comparison and analysis, it is obvious that the proposed method has a good stable and rapid convergence property and the results of this paper closely agree with those obtained by published literatures, FEM and experiment. In addition, some interesting results about free vibration characteristics of FG doubly-curved shells are investigated.
       
  • Cyclic behavior of hybrid rc columns using high-performance
           fiber-reinforced concrete and ni-ti sma bars in critical regions
    • Abstract: Publication date: Available online 6 January 2019Source: Composite StructuresAuthor(s): Javier Pereiro-Barceló, José L. Bonet, Beatriz Cabañero-Escudero, Begoña B. Martínez-Jaén Thanks to their excellent deformation capacity and ductility, smart materials are now being increasingly used in the construction industry, one example being superelastic Shape Memory Alloys (SMA) such as Ni-Ti, which can recover from large strains without generating significant residual strains.The purpose of this work was to study the behavior under cyclic loading of hybrid-reinforced concrete columns containing super-elastic Ni-Ti bars and High-Performance Fiber-Reinforced Concrete (HPFRC) in their critical end regions, where plastic hinges may form (column ends). This critical region is a dissipative zone of the column where the most adverse combination of actions occurs.An experimental study was carried out to simulate inter-story columns in which the effects of the axial level and continuous or discontinuous beam-column joints were analyzed. The specimens with continuous joints were found to display greater lateral strength, ductility and energy dissipation, while those with discontinuous joints underwent smaller residual displacements and less damage in the critical regions of the columns.
       
  • Modeling on bearing behavior and damage evolution of single-lap bolted
           composite interference-fit joints
    • Abstract: Publication date: Available online 6 January 2019Source: Composite StructuresAuthor(s): Junshan Hu, Kaifu Zhang, Yunwei Xu, Hui Cheng, Guanhua Xu, Hailin Li This paper deals with the modeling of bearing behavior and damage evolution of single-lap bolted composite interference-fit joints. Shear nonlinearity constitutive relations for composites are defined with the Ramberg-Osgood equation. The anisotropic damage model established on continuum damage mechanics incorporates extended 3D failure criteria and exponential damage evolution rule to describe damage initiation and material stiffness degradation, respectively. Numerical simulations of composite joints based on the proposed model under varying interference-fit sizes, bolt preload levels and composite layups are conducted and validated by experimental tests. Results show the interface voids of joint-hole in micro-scale left by hole-drilling would compensate part of the nominal interference-fit size and make the real fit sizes smaller than the numerical ones. The strain contours and hyperechoic strips detected in bearing specimens are accurately characterized by damage patterns in joint models, whereas the predicted load-displacement behavior shows over-conservative errors caused by excessive bolt inclination. The fiber breakage and matrix crushing in micro-morphology on the bearing plane are well captured in numerical model, suggesting robust ability of the proposed model in application.
       
  • Prediction of mechanical properties of carbon fiber based on cross-scale
           FEM and machine learning
    • Abstract: Publication date: Available online 6 January 2019Source: Composite StructuresAuthor(s): Qi Zhenchao, Zhang Nanxi, Liu Yong, Chen Wenliang Carbon fiber is the most common reinforcing phase in composite materials. However, it is difficult to obtain the performance parameters of the monofilament. In this study, the relationship between the property variables of the carbon fiber monofilament and the macroscopic parameters of the composites is established using a regression tree, a type of decision tree model, in machine learning. First, in order to obtain the data for machine learning, representative volume element (RVE) models of single-layer and multi-layer carbon fiber reinforced plastic (CFRP) are established by a cross-scale finite element method (FEM), and periodic boundary conditions are loaded. Then, a correlation model between the carbon fiber properties and CFRP and matrix properties is established. The non-GUI mode is called by Software Isight to generate the sample data. Second, in order to avoid overfitting, the L1 norm method is used for feature selection before model training. Finally, the four elastic properties of the carbon fiber are analyzed by a regression tree model. After a series of parameter adjustments and model selection, the model with a better generalization performance was obtained. The validity of the models was verified by the validating sample set.
       
  • Development of a computational predictive model for the nonlinear in-plane
           compressive response of sandwich panels with bio-foam
    • Abstract: Publication date: Available online 6 January 2019Source: Composite StructuresAuthor(s): Wong Yong Jie, Senthil Kumar Arumugasamy, K.B. Mustapha In this study, sandwich structures with a commercial-grade aluminium alloy and bio-inspired core (mycofoam) were fabricated and tested to obtain the axial compression response in terms of in-plane deformation measures and stress. The ensuing spectrum of response data from experimental tests were then fed into three different data driven models that include simple linear regression (SLR), artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS). The performance of the models is compared in estimating the compressive response of sandwich panels with the mycofoam. To access the performance of models, coefficient of determination (R2), root mean squared error (RMSE) and mean absolute error (MAE) are used. 11 different training algorithms are tested in ANN and Bayesian Regularization backpropagation. 9 hidden neurons is found to be the optimum ANN structure. In ANFIS model, triangular-shaped MF with 20 rules gives the highest performance among 8 different MFs. All three models are found to be capable in estimating the compressive response. ANFIS model has the highest performance, followed by ANN model then SLR model with R2, RMSE and MAE are 0.9999, 0.0818, 0.0415 for the training dataset; 0.9999, 0.1626, 0.0491 for the testing dataset and 0.9999, 0.0943, 0.0437 for the validation dataset, respectively.
       
  • A Closed-Form Analytical Solution Method for Vibration Analysis of
           Elastically Connected Double-Beam Systems
    • Abstract: Publication date: Available online 6 January 2019Source: Composite StructuresAuthor(s): Shibing Liu, Bingen Yang A double-beam system, which is a structure composed of two parallel beams that are interconnected by a viscoelastic layer, is seen in many engineering applications. Vibration analysis is essentially important for the safe, reliable, and optimal design of such dynamic systems. This paper presents an analytical method, the distributed transfer function method (DTFM), for modeling and vibration analysis of double-beam systems with arbitrary beam linear densities, beam flexural rigidities, and boundary conditions. Exact closed-form analytical solutions for natural frequencies, mode shapes, and steady-state responses to periodic excitations are determined. The proposed method is applicable to a double-beam system with lower beam being fully, partially, or not supported by an elastic foundation. Through numerical study, the accuracy and efficiency of the proposed method are validated, and effects of the stiffness, length, and location of an elastic foundation are investigated. It is shown that the DTFM is a useful tool for optimal design of elastically connected double-beam systems.
       
  • Thermal Vibration Analysis of Cracked Nanobeams Embedded in an Elastic
           Matrix Using Finite Element Analysis
    • Abstract: Publication date: Available online 6 January 2019Source: Composite StructuresAuthor(s): A.I. Aria, M.I. Friswell, T. Rabczuk In this study, a finite element (FE) model is proposed to study the thermal transverse vibrations of cracked nanobeams resting on a double-parameter nonlocal elastic foundation. Hamilton’s principal is employed to derive the governing equations for the free vibrations of the nanobeam. The cracked section of the beam is modelled by dividing the cracked element into two classical beam sections connected via a rotational spring positioned at the crack. The Galerkin method of weighted residuals is used to solve the equations of motion and calculate the natural frequencies. The effect of the crack length, crack position, the temperature gradient, the boundary conditions and the foundation stiffness, on the vibration response of the cracked nanobeams supported by elastic foundations is considered by including thermal effects. The FE results are compared to the available benchmark studies in the literature.
       
  • Analytical and experimental investigation on bond behavior of
           CFRP-to-stainless steel interface
    • Abstract: Publication date: Available online 6 January 2019Source: Composite StructuresAuthor(s): Hongyuan Tang, Xuezhi Deng, Zhinbin Lin, Xiang Zhou Steel structures using stainless steel are recently accepted as more sustainable and durable systems. Although much research has been conducted on steel structures strengthened by carbon fiber-reinforcement polymer (CFRP) material, these steel structures are often made of conventional mild steel and thus existing prediction and analysis specified for mild steel cannot be directly extended for that of stainless steel. Therefore, this study aims to develop a new prediction model for determining the bond behavior of CFRP-to-stainless steel. Load time-history bond behavior was formulated in a piecewise manner to account for varying elastic, elastoplastic and debonding stages. A total of 22 stainless steel plates bonded with CFRP laminates were fabricated and tested to calibrate the model and further quantify the critical design parameters, including layers and anchorage length. Observation of the experiment showed that debonding failure between the adhesion layer and the CFRP sheets was dominant, partially suggesting the linear stress-strain relation for the CFRP and stainless steel. Comparison of results predicted by the proposed model to the test ones demonstrated that the proposed model has a high accuracy in prediction of bond stress and bond strength.
       
  • A third order nonlinear model to study the dynamic behaviour of composite
           laminated structures under thermal effect with experimental verification
    • Abstract: Publication date: Available online 4 January 2019Source: Composite StructuresAuthor(s): Moumita Sit, Chaitali Ray The present article includes the modal analysis of laminated composite structures under thermal effect. Experiments are conducted to study the influence of temperature change on natural frequencies of glass fibre reinforced polymer (GFRP) composites. GFRP laminated plates are prepared in the laboratory using vacuum bagging by resin infusion. The specimens are thermally conditioned to obtain temperature variation ranging from (-) 10°C to 120°C. A Green–Lagrange nonlinear finite element (FE) model based on third order shear deformation theory (TSDT) has been developed for the analysis. The FE solutions in terms of natural frequencies are compared with experimental data and an extensive parametric study is carried out. The free vibration modal analysis of a hollow stiffened laminated panel is also carried out to identify the effect of temperature change with proper temperature distribution within the stiffened structures using 1D heat conduction model and the solutions may be used as benchmark.
       
  • Numerical study of size effects in micro/nano plates by moving finite
           elements
    • Abstract: Publication date: Available online 4 January 2019Source: Composite StructuresAuthor(s): M. Repka, V. Sladek, J. Sladek Bending of plates subjected to stationary transversal loading is studied within the strain-gradient elasticity. The complete formulation including the governing equations and boundary conditions is re-derived for the thin elastic functionally graded as well as homogeneous plate starting from the unified formulation admitting the assumptions of three plate bending theories [46]. The second-order strain gradient theory of elasticity (proposed by Mindlin) with using one microstructural length-scale parameter is employed instead of classical elasticity. Although the derived formulation for thin plate is simpler than for thick plates, it involves the 6th order derivatives of deflections instead of the 4th order derivatives in the classical elasticity. The original system of governing equations is decomposed into the system of 2nd order partial differential equations and new approximation method (MFE – moving finite elements) is proposed for numerical implementation of the derived formulation. The numerical experiments are performed for study the stability, convergence and efficiency of the method as well as for study of the size-effect in micro/nano plates.
       
  • Shear strength of steel fiber-unconfined reinforced concrete beam
           simulation: Application of novel intelligent model
    • Abstract: Publication date: Available online 4 January 2019Source: Composite StructuresAuthor(s): Behrooz Keshtegar, Mansour Bagheri, Zaher Mundher Yaseen The research promotes a new nonlinear model-based hybridized response surface method (RSM) and support vector regression (RSM-SVR) to predict shear capacity of steel fiber-reinforced concrete beams (SFRCB). Two approaches are integrated using RSM which is calibrated based on two input datasets; whereas, the SVR is calibrated based on all the predicted datasets generated by RSM. The high-cross correlation of the input dataset is provided using two nonlinear steps for modeling the SFRCB shear strength. The capacity of hybrid RSM-SVR model is validated with stand-alone intelligent models RSM, SVR and neural network (NN) in addition to eight empirical formulations. The dataset of 139 laboratory experimental tests of shear failure capacity belongs to SFRCB without stirrups, are obtained from the literature. The effects of fiber volume and the longitudinal steel ratio on the shear predictions of the normal and high-strange concrete reinforced by steel fiber are compared for the intelligent and empirical based approaches. The achieved results indicated the RSM-SVR model performed superior prediction over the comparable models. The improved agreement indexes using the RSM-SVR were improved with (0.35 and 1.9) over the empirical formulations and with (0.8, 1.2 and 3.5) over the three intelligent models of RSM, SVR and NN, respectively.
       
  • Bond Durability of CFRP Laminates-to-Steel Joints Subjected to Freeze-Thaw
    • Abstract: Publication date: Available online 4 January 2019Source: Composite StructuresAuthor(s): Yongming Yang, Manuel A.G. Silva, Hugo Biscaia, Carlos Chastre The degradation mechanisms of bonded joints between CFRP laminates and steel substrates under severe environmental conditions require more durability data and studies to increase the database and better understand their causes. Studies on bond properties of double-strap CFRP-to-steel bonded joints with two different composite materials as well as adhesive coupons subjected to freeze-thaw cycles for 10,000 h were conducted to reduce that gap. In addition, the equivalent to the number of thermal cycles and their slips induced in the CFRP laminates was replicated by an equivalent (mechanical) loading-unloading history condition imposed by a static tensile machine. The mechanical properties of the adhesive coupons and the strength capacity of the bonded joints were only slightly changed by the artificial aging. It was confirmed that the interfacial bond strength between CFRP and adhesive is critically related to the maximum shear stress and failure mode. The interfacial bond strength between adhesive and steel degraded with the aging. However, the equivalent thermal cyclic bond stress caused no detectable damage on the bond because only the interfacial elastic regime was actually mobilized, which confirmed that pure thermal cycles aging, per se, at the level imposed, have a low impact on the degradation of CFRP-to-steel bonded joints.
       
  • Effect of machining parameters and cutting tool coating on hole quality in
           dry drilling of fibre metal laminates
    • Abstract: Publication date: Available online 4 January 2019Source: Composite StructuresAuthor(s): K. Giasin, G. Gorey, C. Byrne, J. Sinke, E. Brousseau Fibre metal laminates (FMLs) are a special type of hybrid materials, which consist of sheets of metallic alloys and prepregs of composite layers stacked together in an alternating sequence and bonded together either mechanically using micro hooks or thermally using adhesive epoxies. The present paper contributes to the current literature by studying the effects of three types of cutting tool coatings namely TiAlN, AlTiN/TiAlN and TiN on the surface roughness and burr formation of holes drilled in an FML commercially known as GLARE®. While the cutting tool geometry is fixed, the study is also conducted for a range of drilling conditions by varying the spindle speed and the feed rate. The obtained results indicate that the spindle speed and the type of cutting tool coating had the most significant influence on the achieved surface roughness metrics, while tool coating had the most significant effect on burr height and burr root thickness. The most important outcome for practitioners is that the best results in terms of minimum roughness and burr formation were obtained for the TiN coated drills. However, such drills outperform the other two types of tools, i.e. with TiAlN and AlTiN/TiAlN coatings, only when used for short series of hole drilling due to rapid tool deterioration.
       
  • Absolute frequency analysis of traveling waves in a thin-wall laminated
           composite cylindrical shell rotating on two-ending elastic supports
    • Abstract: Publication date: Available online 4 January 2019Source: Composite StructuresAuthor(s): Abolfazl Rahimi-Moghaddam, Mohammad Danesh, Keivan Torabi In this paper, some methods to determine the absolute frequencies of traveling waves in a rotating cross-ply laminated cylindrical shell with elastic supports are investigated. Based on the Sanders’ shell theory and by taking into account the Hamilton principle, the governing equations of motion are derived in the rotating coordinate system, which considers the effects of initial hoop tension, the centrifugal and the Coriolis forces due to the rotation as well. The constraint equations of elastic supports are modelled by using artificial distributed elastic springs in the possible directions. By substitution of mode shape profile functions into equations and using the differential quadrature method, the eigenvalue equations of the rotaing shell are derived in both rotating and fixed systems. To make more comparison, the eigenvalue equation of synchronous critical speeds is also derived. Convergence and comparison of the proposed method is investigated through comparing its results with available literature. The comparison results shows that the direction of the corresponding traveling waves and the graphical determination of critical speeds are determined by a more convenient criteria with easier physical interpretation in the fixed system, specially by using the direct method which is more efficient in computation than the converting method.
       
  • Nonlinear Finite Element Analysis of Composite Precast Concrete Sandwich
           Panels made with Diagonal FRP Bar Connectors
    • Abstract: Publication date: Available online 3 January 2019Source: Composite StructuresAuthor(s): Qian Huang, Ehab Hamed Composite precast concrete sandwich panels made with diagonal FRP bar connectors have increasingly been used in the last few decades mainly due to their excellent thermal insulating properties. However, there is a lack of standards, design guidelines and reliable models that can be used for their analysis and design. In this paper, a finite element model is developed for investigating their structural behaviour, which aims to clarify their response and to provide a basis for establishing design guidelines. The model accounts for cracking and tension stiffening, material nonlinearity of concrete in compression, and geometric nonlinearity. The modelling challenges and assumptions are investigated, and the model is validated by comparing with other models and test results from the literature. The results explain the structural behaviour of these panels, which exhibit a partial composite action. The results also show that the failure mode of typical panels is ductile and dominated by yielding of the flexural steel reinforcement. A preliminarily investigation of the thermal effects shows that temperature gradients can lead to significant arching action in the panel and can affect its stability. The influence of the diameter and shape of the shear connectors and the stiffness of the insulation are investigated.
       
  • Microwave Curing of Multidirectional Carbon Fiber Reinforced Polymer
           Composites
    • Abstract: Publication date: Available online 3 January 2019Source: Composite StructuresAuthor(s): Yingguang Li, Nanya Li, Jing Zhou, Qiang Cheng Composite microwave curing technologies have been researched and given great expectations for decades to cutting down the long curing cycle and enormous energy consumption during traditional curing process. However, this good vision was stopped since the microwave can hardly penetrate and heat multidirectional carbon fiber reinforced polymer composites. In this paper, the mechanism that multidirectional composite can hardly be heated was revealed. New method was found to stimulate Vertical Penetrating Microwave (VPM) by using metal strips, and the multidirectional carbon fiber reinforced polymer composites can be heated directly. The theory and model of VPM’s heating depth of multidirectional composite were established and verified. The results indicated that 2.3mm thickness multidirectional composite can be cured effectively by using the VPM.
       
  • Behavior of Circular CFRP-Steel Composite Tubed High-Strength Concrete
           Columns under Axial Compression
    • Abstract: Publication date: Available online 3 January 2019Source: Composite StructuresAuthor(s): Jiepeng Liu, Tianxiang Xu, Ying Guo, Xuanding Wang, Y. Frank Chen Application of high strength concrete (HSC) is an effective way to reduce the column size in high-rise and large-span structures, resulting in more available floor space. The concern on the brittleness of HSC can be alleviated by providing some confinement to it. To this end, carbon fiber reinforced polymer (CFRP) and steel tube are found to be very effective. This paper presents experimental and theoretical studies on the axial behavior of CFRP-steel composite tubed HSC columns. Totally, 25 specimens were tested to investigate the influences of CFRP layers, diameter-to-thickness ratio of steel tube, and concrete strength on the load bearing capacity and deformation behavior of such composite members. The observed failure modes, stress-strain relationships, stresses of steel tubes, and deformations of concrete are discussed. The experimental results indicate that with enough CFRP sheets the load bearing capacity and deformation behavior of core concrete are significantly improved, especially the ductility of specimens with concrete strength of 105MPa. Calculation methods for the axial load bearing capacity of a CFRP-steel composite tubed HSC column are presented and discussed.
       
  • Nonlinear bending of sandwich beams with functionally graded negative
           Poisson’s ratio honeycomb core
    • Abstract: Publication date: Available online 3 January 2019Source: Composite StructuresAuthor(s): Chong Li, Hui-Shen Shen, Hai Wang This paper investigates the nonlinear bending behavior of sandwich beams with functionally graded (FG) negative Poisson’s ratio (NPR) honeycomb core in thermal environments. The novel constructions of sandwich beams with three FG configurations of re-entrant honeycomb cores through the beam thickness direction are proposed for the first time. The temperature-dependent material properties of both face sheets and core of the sandwich beam are considered. 3D full scale finite element analyses are conducted to investigate the nonlinear bending behavior and the variation of effective Poisson’s ratio (EPR) of the sandwich beam in the large deflection region. The numerical simulations are carried out for the sandwich beams with FG-NPR honeycomb core, from which results for the same sandwich beam with uniform distributed NPR honeycomb core are obtained as a comparator. Finite element results showed that the thickness change of sandwich beams with NPR honeycomb cores are distinctly out of ordinary, and the NPR sandwich beams have significantly lower load-bending moment curves compared with those with positive Poisson’s ratio cores. The effects of functionally graded configurations, load distribution types, boundary conditions, temperature changes and length-to-thickness ratios on the bending load-deflection curves and EPR-deflection curves of sandwich beams are discussed in detail.
       
  • On using load-axial shortening plots to determine the approximate buckling
           load of short, real angle columns under compression
    • Abstract: Publication date: Available online 3 January 2019Source: Composite StructuresAuthor(s): Andrzej Teter, Zbigniew Kolakowski In the present paper, a methodology for determination of an approximate value of the lowest buckling load of the thin-walled column under compression and with an arbitrary cross-section, affected by initial imperfections, whose amplitude does not exceed half the thickness of the wall, using a load-axial shortening plot, is presented. It has been shown that the load corresponding to an alternation in rigidity of the real structure on the load-axial shortening plot determines the buckling load with high accuracy. The attained results have been compared to the values corresponding to the bifurcation load and the lowest buckling loads determined with commonly used methods based on post-buckling equilibrium paths (i.e., P-w method, P-w2 method, inflection point method).The formulated problem of nonlinear buckling has been solved with the analytical-numerical method and the FEM. An influence of the imperfection amplitude on an approximate value of the lowest buckling load of laminated thin-walled structures has been analysed on the determined post-buckling equilibrium paths and the load-axial shortening plot. Non-symmetric configurations of laminate layers that additionally exhibit various types of the membrane and bending state coupling have been selected. Detailed computations have been conducted for short angle sections (i.e. angle columns) under uniform compression.
       
  • Macro-mechanical Modeling and Experimental Validation of Anisotropic,
           Pressure- and Temperature-dependent Behavior of Short Fiber Composites
    • Abstract: Publication date: Available online 23 December 2018Source: Composite StructuresAuthor(s): A. Dean, N. Grbic, R. Rolfes, B. Behrens In this article, firstly a comprehensive experimental characterization of short fiber reinforced plastic (SFRP) composites sheets is presented. The micro-computed tomography (μCT) is utilized at first to analyze the degree of anisotropy of the SFRP sheets. Then, destructive tests are applied to investigate the mechanical behavior of the sheets at different loading states. The experimental results are presented and discussed thoroughly. Secondly, based on the findings from the experiments conducted, the numerical modeling of the SFRP sheets is discussed. Therein, a user-defined macro-mechanical constitutive model is suggested to represent the sophisticated constitutive behavior of SFRP composites. A brief description of the model and the parameter identification is provided. The performance of the model is assessed and verified via the FE simulation of the destructive characterization tests. Furthermore, the model is employed in the simulation of biaxial stretching experiments of SFRP sheets. The experimental-numerical correlation results demonstrate the validity, accuracy and applicability of the employed modeling procedure.
       
  • Estimations of the debonding process of aged joints through a new
           analytical method
    • Abstract: Publication date: Available online 21 December 2018Source: Composite StructuresAuthor(s): Hugo C. Biscaia, Carlos Chastre, Manuel A.G. Silva The estimation of the long-term durability of adhesively bonded interfaces between Fiber Reinforced Polymers (FRP) and concrete substrates is crucial because degradation potentiates FRP premature debonding. One of the main reasons for mistrusting the use of FRP composites is the premature debonding phenomenon, which, associated to degradation, has been preventing their widespread use. In this research work, an analytical model is proposed that introduces aging to estimate the effects of degradation of Glass (G) FRP externally bonded to concrete. Cycles were used to experimentally accelerate aging of beam specimens, namely, (i) salt fog cycles; (ii) wet-dry cycles with salted water; (iii) temperature cycles between -10°C and +30°C; and (iv) temperature cycles between +7.5°C and +47.5°C. Based on the experimental results obtained and a corresponding bond-slip curve, the analytical model predicts the complete debonding process between FRP composites and a substrate. Consequently, the temporal evolution of the degradation of the bonded interfaces can be calculated and compared with the initial situation prior to exposure. The effects of the environmental conditions are reported and compared.
       
  • Experimental Investigation and Probabilistic Models for Residual
           Mechanical Properties of GFRP Pultruded Profiles Exposed to Elevated
           Temperatures
    • Abstract: Publication date: Available online 19 December 2018Source: Composite StructuresAuthor(s): Esmaeil Pournamazian Najafabadi, Mohammad Houshmand Khaneghahi, Hossein Ahmadie Amiri, Homayoon Esmaeilpour Estekanchi, Togay Ozbakkaloglu Here, we investigate the influence of elevated temperatures with negligible ambient oxygen on mechanical properties of various embedded glass fiber reinforced polymer (GFRP) profiles, as well as the application of a predictive Bayesian model for predicting these properties. Both the flexural and compressive properties of FRP profiles were investigated through the tests of I-shaped and box-shaped profiles. To determine the impact of low and high elevated temperature, the profiles were exposed to a wide range of temperatures (i.e., 25 to 550°C); effects of the exposure time were also investigated. Experiments showed that specimens exposed to higher elevated temperatures for longer time periods lose more of their mechanical properties. We used profiles in a simulated embedded environment to prevent combustion and charring, thus reducing fire vulnerability of the GFRP material at high elevated temperatures. We found that elevated temperature for 15 min produces slight strength deterioration in the embedded FRP profiles. Also, exposure to a high elevated temperature for 45min reduced the maximum loads by up to 30%. Next, we performed a filled emission scanning electronic microscopy (FE-SEM) study before and after the mechanical tests to examine both the control specimens and conditioned specimens that were exposed to elevated temperatures. This approach allowed us to investigate the microscale effect of the elevated temperatures as well as the failure mode mechanisms of FRP profiles under flexure and compression. The micrographs revealed that a glut of small cracks formed in FRP profiles exposed to high elevated temperatures, leading to sole resin failure in the mechanical tests. Finally, Bayesian linear regression was applied to the laboratory test results, which led to a predictive model for mechanical properties of FRP profiles exposed to elevated temperatures.Graphical abstractGraphical abstract for this article
       
  • High strain rate compressive behaviors and adiabatic shear band
           localization of 3-D carbon/epoxy angle-interlock woven composites at
           different loading directions
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Junjie Zhang, Meiqi Hu, Shengkai Liu, Lei Wang, Bohong Gu, Baozhong Sun When serving as a lightweight structural member in many areas, the dynamic mechanical behavior of fiber-reinforced polymeric matrix composites, especially under different strain rates, means a lot to the optimization of structure design as to high-speed impact. Under different loading rates and directions, we experimentally and numerically investigated the strain rate effect on the impact compressive behavior of 3-D angle-interlock woven composites (3-D AWCs) composed of carbon fiber and epoxy resin. Based on the factual geometrical architecture of 3-D AWC, the meso-scale model, which considers the interfacial damage between the reinforcements and matrix, was established to visually characterize the deformation history and damage morphologies of 3-D AWCs during impact compression process. Further, we performed high strain rate compressive tests on the split Hopkinson pressure bar (SHPB) apparatus integrated with a high-speed photography system for capturing images of progressive damage process to validate the proposed mesoscopic model. The stress-strain curves of various strain rates show strain rate effect varies depending on loading direction. The rate sensitivity on the compressive failure strength exists at weft direction and through-thickness direction except for warp direction. Moreover, both from images and finite element model results, the localized adiabatic shear band induced by intense plastic strain, initiates mainly from epoxy resin matrix and propagates along the interface at all three loading directions.
       
  • Numerical and experimental study on deformation of 3D-printed polymeric
           functionally graded plates: 3D-Digital Image Correlation approach
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Maedeh Amirpour, Simon Bickerton, Emilio Calius, Raj Das, Brian Mace This paper presents a novel experimental and simulation investigation of quasi-static transverse deformation of 3D printed polymeric Functionally Graded (FG) plates, which obey the distribution of material properties through the length. Graded solid elements with continuous property distribution at different Gauss points were implemented by a user material subroutine (UMAT) in ABAQUS Finite Element (FE) software. In order to validate the proposed graded FE solutions, the original experimental deflection measurements using 3D-Digital Image Correlation (DIC) technique performed to capture transverse deformation of designed and manufactured 3D printed polymeric FG plates. DIC technique involved tracking the motion of geometric features on a specimen surface over the course of an experiment to generate the displacement field experimentally. It was found that the deviation between FE and experimental out of plane deflection for nonlinear FG plates is higher than that of linear FG plates, which is potentially due to the high gradient distribution of the material inclusions. It can be concluded that the presented 3D-digtal image correlation technique provides for transverse deformation of polymeric FG plates. The deflection contours for the FG plate are not symmetric, differences being more prominent for the linear high stiffness ratio combination. The outcomes of this study can be applied to determine the optimum material distribution to produce a controlled-stiffness polymeric FG plate corresponding to prescribed structural characteristics.
       
  • Experimental and numerical studies on the low-velocity impact response of
           orthogrid epoxy panels reinforced with short plant fibers
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): K. Hamamousse, Z. Sereir, R. Benzidane, F. Gehring, M. Gomina, C. Poilâne Experimental and numerical studies were conducted to analyze the low-velocity impact response of orthogrid stiffened panels reinforced with short alfa fibers. Tensile specimens and orthogrid panels were fabricated with two types of epoxy resins and different fractions of crushed and sieved alfa fibers (fiber volume fraction (Vf) from 10% to 50%). Impact tests were conducted on the orthogrid panels to investigate their low-velocity transverse impact behavior. The resistance to damage increased with an increase in fiber content and improvement in the mechanical properties of the composites (measured in static). Bending tests carried out on pre-impacted and non-impacted panels revealed a change in the linearity of the initial bending behavior, which could be justified by the small cracks generated by impact. A numerical model of impact on the orthogrid stiffened composite panels was developed using the nonlinear Hertz’s contact model. To simulate the failure mechanism and load-time history, a standard Tsai-Wu failure criterion was used on ANSYS explicit dynamic software. The simulations show a good correlation with the experimental data. The dominant stresses for damage evolution are found to be normal stresses. The presence of a stiffener reduces the stress, which confirms that stiffeners limit the propagation of damage.
       
  • Flexural response of continuous unbonded post-tensioned beams strengthened
           with CFRP laminates
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Wei Zhou, Xinying Xie The sudden brittle rupture of carbon fiber-reinforced polymer (CFRP) materials is often confused with the redistribution capacity of statically indeterminate CFRP-strengthened structures. Few investigations have been carried out regarding the flexural behavior of continuous CFRP-strengthened unbonded post-tensioned (UPT) beams, despite such beams having been extensively applied in practice, owing to retrofitting alternatives. This study emphasizes the flexural response of continuous UPT beams strengthened with CFRP laminates subjected to monotonic loading to failure. Progressive fracture of the CFRP laminates appears in the hogging and sagging regions, accompanied by concrete crushing in the sagging regions. The degree of moment redistribution (MR) and ductility generally increase with decreasing compressive zone depth of the critical section over the inner support. When the ratio of the global reinforcement index of the inner support to that of the mid-span increases, the MR and ductility decrease.
       
  • Thermal postbuckling behavior of FG-GRC laminated cylindrical panels with
           temperature-dependent properties
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Hui-Shen Shen, Y. Xiang, J.N. Reddy The current study deals with thermal postbuckling behavior of graphene-reinforced composite (GRC) laminated cylindrical panels resting on elastic foundations. The GRC layers of the panel are arranged in a piece-wise functionally graded (FG) distribution along the thickness direction, and each layer of the panel contains different volume fractions of graphene reinforcement. The temperature dependent material properties of GRCs are estimated by the extended Halpin–Tsai micromechanical model with graphene efficiency parameters being calibrated against the GRC material properties obtained from the molecular dynamics simulations. The nonlinear governing equations for the thermally-loaded GRC laminated cylindrical panels are derived based on the higher order shear deformation theory and include the geometric nonlinearity effects in the sense of the von Kármán nonlinear kinematic assumptions. The panel-foundation interaction and thermal effects are also considered. The thermal postbuckling equilibrium paths for the perfect and geometrically imperfect GRC laminated cylindrical panels are obtained by applying a singular perturbation method in conjunction with a two-step perturbation approach. An iterative scheme is developed to obtain the numerical thermal postbuckling solutions of the panels. We observe that the piece-wise functionally graded distribution of graphene reinforcement can enhance the thermal postbuckling strength of the GRC laminated cylindrical panel under a uniform temperature field.
       
  • Deformation sensing and electrical compensation of smart skin antenna
           structure with optimal fiber Bragg grating strain sensor placements
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Jinzhu Zhou, Zhiheng Cai, Le Kang, Baofu Tang, Wenhua Xu Skin antenna structure is a kind of multifunctional composite structure in which printed antennas are integrated. This paper proposes a new smart skin antenna structure with embedded fiber Bragg grating (FBG) strain sensors. Utilizing the measured strains from limited FBG strain sensors, the deformation shapes are reconstructed by using a strain–displacement transformation, and the deteriorated radiation patterns caused by the deformations are compensated by using a strain-electromagnetic coupling mode which is derived and validated for the first time in the paper. Moreover, a two-step sensor placement method considering the information redundancy is proposed to determine optimal FBG strain sensor locations. The comparisons show that the two-step sensor placement method is advantageous in terms of the sensor distribution and computational cost. The fabrication process of the smart skin antenna structure was presented, and an experimental system with optimal sensor placements was developed. The measured results demonstrate that the reconstructed shapes agree well with the real ones, and that the deteriorated radiating patterns were almost completely restored to the desired ones. The proposed smart skin antenna structure which can provide the electromagnetic receiving-sending, structural deformation monitoring and electrical correction functions has a potential application prospect in the future mobile vehicle.
       
  • Impact localization of composite stiffened panel with triangulation method
           using normalized magnitudes of fiber optic sensor signals
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Byeong-Wook Jang, Chun-Gon Kim The triangulation method has been an effective tool for estimating the source locations of various acoustic emissions (AE). However, it is hard to guarantee high accuracy in composite structures due to their anisotropy. Also, the conventional methods basically require the precise arrival time data of AE signals. Because most of commercial fiber optic sensing systems applicable to real structures have limited measurement performance, the arrival times cannot be clearly identified. In this paper, the magnitudes of fiber optic sensor signals were used for estimating the distances between each sensor and impact location. In order to obtain higher correlation between the magnitude and distance, the signal near the roughly estimated arrival time was used for calculating the magnitude. Then, through the neural network training, the accuracy of estimating the distances from the signal magnitudes could be enhanced. Finally, the triangulation method was applied for localizing the impact sources. As a result, our suggested triangulation method showed the acceptable localization results about the non-trained impact points. Because the input data for this method could be reliably obtained from the commercial fiber optic sensing system, it can be useful for constructing a simple impact monitoring system for the real composite structures.
       
  • Effect of fiber loading directions on the low cycle fatigue of intraply
           carbon-Kevlar reinforced epoxy hybrid composites
    • Abstract: Publication date: Available online 5 January 2019Source: Composite StructuresAuthor(s): Nurain Hashim, Dayang Laila Abdul Majid, El-Sadig Mahdi, Rizal Zahari, Noorfaizal Yidris Effect of fiber orientation on tensile and low cycle fatigue of intraply hybrid composites was investigated. In this work, intraply carbon/Kevlar fabric/epoxy hybrid composites were tested for static and cyclic loadings at 0°, 45 and 90° corresponding to carbon, off-axis and Kevlar fiber directions. Ambient fatigue tests were performed at stress levels established from static tests. Tensile results showed the best strength and modulus was in the carbon direction followed by Kevlar direction. At 45°, high ductility was observed associated to fiber rotation. Fatigue linear regression lines indicated a slower degradation rate in the Kevlar loading direction compared to the carbon loading direction. Large fatigue scatter in the Kevlar direction suggested two distinct phases of fatigue attributed to the stiffening of Kevlar fibers that further led to lower fatigue degradation. Investigation on residual strength of run-out samples and fracture modes were also presented with interesting findings.
       
  • Uniaxial Compression Mechanical Properties and Fracture Characteristics of
           Brucite Fiber Reinforced Cement-Based Composites
    • Abstract: Publication date: Available online 5 January 2019Source: Composite StructuresAuthor(s): Yuanyi Yang, Yi Deng, Xingkui Li In this work, the mechanical properties, stress-strain behaviors, and microstructure of brucite fiber reinforced cement-based composites are determined. The results reveal that the incorporation of brucite fiber limits the compressive strength reinforcement of cement-based composite but leads to a significant increase of tensile strength by 136% and flexural strength by 73%. The employment of brucite fiber increases the fracture toughness KIcS and KIcQ of the cement-based composite by 450% and 98%. The incorporation of brucite fiber increases the linear elastic fracture toughness energy GF by 455% and elastic-plastic fracture toughness energy JC by 279%. The constitutive model of brucite fiber reinforced cement paste is also established. The diameter of the brucite fiber bundle is 1.5-16.3μm, and the diameter of the single dispersed fiber is around 45-110nm. There are about 15-363 single fibers in a bundle. Due to the brucite fiber possesses an intrinsic fibrous anisotropy, and network topology, the brucite fiber reinforced cement composites exhibit advantages of greater bending strength and crack bridging, as well as better crack resistance properties.
       
  • Digital image correlation (DIC) for measurement of strains and
           displacements in coarse, low volume-fraction FRP composites used in civil
           infrastructure
    • Abstract: Publication date: Available online 4 January 2019Source: Composite StructuresAuthor(s): Enrique del Rey Castillo, Tom Allen, Richard Henry, Michael Griffith, Jason Ingham Accurately measured strains are critical when investigating the application of Fiber Reinforced Polymer (FRP) materials, but traditional mechanical strain measurement methods have several critical drawbacks related to the installation process and the recording capabilities of the devices. FRP materials typically used in the civil engineering field feature large asymmetries and heterogeneity originated from the manual installation procedures, as opposed to the highly controlled FRP fabrication methods used in other fields that result in more homogeneous materials. The feasibility of using an optical full-field Digital Image Correlation (DIC) technique for measurement of strain fields on FRP materials used in the civil engineering industry has been investigated and the level of error in the DIC method when using more traditional methods was determined. The main advantage of using DIC over more traditional methods, which is the capacity of DIC to measure full field strains instead of strains at isolated points, has been demonstrated by providing exemplar measurements of various specimens of FRP materials. The reported strain fields are examples of what was obtained during an experimental campaign to understand the behavior of FRP anchors and other materials. The main conclusions drawn from the observation of those strain fields are discussed.
       
  • Seismic behaviour of RC short shear wall strengthened with externally
           bonded CFRP strips
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Samiullah Qazi, Laurent Michel, Emmanuel Ferrier The present study addresses the applicability of CFRP partial strengthening technique on the short RC walls (weak in shear) to attain reasonable strength and drift without deterioration in the wall energy dissipation capacity, under seismic loading. Three RC walls were tested: one control wall and two walls strengthened with CFRP, using two different bonding configurations. The RC walls represent at 1:3 scale, the lower part of a shear wall of the existing typical five stories building designed prior to seismic loading consideration i.e., in 1960 in Europe (Switzerland and France). The walls were subjected to displacement controlled cyclic lateral loading, accompanied with a constant axial load at the head beam level. The strengthened walls showed satisfactory performance with improved shear strength and drift, compared to the control wall, with negligible deterioration in dissipation capacity. The test results discussion includes stiffness, ultimate load capacity, deformability, and energy dissipation.
       
  • Effect of thermal cycling heated Fibre Metal Laminates under static load
    • Abstract: Publication date: Available online 24 December 2018Source: Composite StructuresAuthor(s): Michiel Hagenbeek, Jos Sinke Heated GLARE, a Fibre Metal Laminate with an integrated heater element, has been developed for de- or anti-icing systems in aircraft structures. Besides cyclic thermal loading these structures are also subjected to mechanical loading. To investigate the effect of static loading in addition to thermal cycling a series of tests have been performed on heated GLARE using a specifically designed mechanical load fixture and thermal cycling setup. Three different tensile stress levels, 150, 200 and 300 MPa, were used in combination with up to 36,000 thermal cycles between -20 and 50 ° C.The effect of the combined thermo-mechanical loading was investigated by testing the interlaminar shear properties of each sample after thermal cycling. Thermal cycling under a 150 MPa static load showed much less reduction or even increase in strength compared to previously reported test results for thermal cycling only. This effect was not found for thermal cycling under the 200 and 300 MPa static load cases. On the contrary, in these cases more reduction in strength was found compared to test results after thermal cycling without static load.
       
  • A two-dimensional elasticity model for bending and free vibration analysis
           of laminated graphene-reinforced composite beams
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Miao Wang, Yong-Gang Xu, Pizhong Qiao, Zhi-Min Li By assuming the plane-stress state in each layer, a two-dimensional elasticity model is proposed for laminated graphene-reinforced composite (GRC) beams. It is assumed that the graphene disperses uniformly in each layer but the graphene volume fraction may vary from layer to layer. For an arbitrary individual layer, the governing partial differential equations and boundary conditions are given directly from the two-dimensional elasticity theory. Then, the multi-term Kantorovich-Galerkin method is employed to build a state-space equation for the layer, in which the axial and transverse displacements are expressed as products of trial function matrix and unknown function matrix. Eventually, a global equation for the laminated beam is established by virtue of the displacement and stress continuity conditions at the interfaces. Non-dimensional displacements, stresses and natural frequencies are obtained for laminated GRC beams with different boundary conditions. The effects of graphene distribution patterns, boundary conditions, length-to-thickness ratios, layer fraction increments and the number of layers are examined. It is found that the laminated GRC beam with graphene distribution pattern X has the smallest deflection and largest fundamental frequency at high length-to-thickness ratios, but it has largest deflection and smallest fundamental frequency at a very low length-to-thickness ratio due to its reduced transverse shear stiffness.
       
  • Effect of wall thickness and cutting parameters on drilling of glass
           microballoon/epoxy syntactic foam composites
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): H.S. Ashrith, Mrityunjay Doddamani, Vinayak Gaitonde Effect of glass microballoon (GMB) wall thickness and cutting parameters (cutting speed, feed and drill diameter) on thrust force (Ft), surface roughness (Ra), specific cutting coefficient (Kf), cylindricity (CYL), circularity error (Ce-Exit) and damage factor (Fd-Exit) in drilling of GMB/epoxy syntactic foam is presented. CNC vertical machining centre is utilised for conducting experiments based on full factorial design. Significant process parameters are identified through response surface methodology. Wall thickness significantly affects the Ce-Exit and CYL of the drilled hole. Increasing wall thickness significantly reduces the Ra (30%), CYL (41%) and Ce-Exit (56%) due to the increased thermal stability of syntactic foams. This observation is very crucial for the syntactic foams used in structural applications pertaining to structural stability. Drill diameter is observed to be significant for Ft, Ra, CYL and Fd-Exit; while Kf is governed by feed. Furthermore, grey relation analysis (GRA) is used to identify the specific combination of process parameters to obtain good quality drilled hole. Combination of higher particle wall thickness and feed, lower cutting speed and drill diameter produces a sound hole quality as observed from GRA. Hole quality is highly influenced by drill diameter followed by cutting speed and GMB wall thickness. The present study offers guidelines for the industries (structural applications) to produce quality holes in GMB reinforced epoxy matrix.
       
  • Review of research on the vibration and buckling of the FGM conical shells
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): A.H. Sofiyev The purpose of this study is to provide an exhaustive review of the literature on the vibration and buckling of functionally graded materials (FGMs), functionally graded conical shells (FGCSs), functionally graded layered conical shells (FGLCSs), and functionally graded sandwich-conical shells (FGSCSs). The methodological solutions for various problems encountered in pure FGCSs and FGSCSs in the design, for example, linear and non-linear (NL) vibration and stability under various loads and the influences of the different environment are presented. The examples of FGM structures included in the review cover a wide range of applications in nuclear, space and marine engineering, electronics and biomedical fields.
       
  • Reliability analysis of blade of the offshore wind turbine supported by
           the floating foundation
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Liqin Liu, Hengdong Bian, Zunfeng Du, Changshui Xiao, Ying Guo, Weichen Jin The reliabilities of the offshore wind turbine blades supported by the floating foundation are studied. The motion of the floating wind turbine is calculated by the Fast software, and the structure model of the blade is established by the Ansys software. The failure probabilities of the blade root overload, the blade root fatigue and the excessive displacement of the blade tip are calculated. The fixed wind turbine blades and the floating wind turbine blades are compared to investigate the influences of the floating foundation motion on the blade reliabilities. The results show that, the failure probability of blades supported by the floating foundation is greater than that supported by the fixed foundation. The floating wind turbine blades with different piezoelectric material are analyzed to investigate the influences of the piezoelectric material on the blade reliabilities. It is shown that for the blade with piezoelectric material, the stress of blade root and the displacement of blade tip both decrease, and the probabilities of fatigue failure and overloaded of the blade root decrease significantly.
       
  • Three-dimensional multifilament finite element models of Bi-2212
           high-temperature superconducting round wire under axial load
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Yang Liu, Xu Wang, Yuanwen Gao We established a three-dimensional (3D) multifilament finite element model for Bi-2212 round wire under axial load and analyzed its mechanical behavior. The model considered the initial thermal residual stress and damage of Bi-2212 superconducting filaments. The proposed model accurately predicted the axial mechanical behavior of strands. In addition, the characteristics of hysteresis loops in the stress–strain curves of Bi-2212 high-temperature superconducting (HTS) round wire under axial cyclic load were also obtained, agreeing well with experimental data. We constructed a 3D multifilament finite element model and 3D homogenized finite element model of a Bi-2212 HTS triplet. Both the results predicted by multifilament finite element model and homogenized model are close to the experimental data. The former gave more accurate stress distribution characteristics of strands than the latter. However, the homogenized model maybe more suitable for modeling of higher-level cables than the triplet model because of its lower computational cost.
       
  • Experimental and numerical analyses of the penetration resistance of
           ceramic-metal hybrid structures
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Chao Tian, Xuanyi An, Qitian Sun, Yongxiang Dong Ceramic-metal hybrid structures have attracted significant attentions as protection structures because of their high anti-penetration performance. In the present study, a ceramic-metal hybrid structure was constructed with a TC4 frame and ceramic prisms, and its anti-penetration performance and mechanism against a vertical steel projectile were investigated experimentally and numerically. The hybrid structure exhibited much higher penetration resistance than the TC4 monolithic plate of equal areal density. It was found that the high anti-penetration performance was mainly attributed to the frame in the structure, which confined the ceramic prisms and effectively improved their penetration resistance. Additional performance improvement was found to derive from the adhesive that bound the ceramic prisms with the frame. The TC4 frame and adhesive prolonged the dwell time of the projectile on the ceramic prisms and significantly dissipated the projectile kinetic energy. In addition, although the hybrid structure in this investigation was heterogeneous, its anti-penetration performance was affected less by the impact position than those of conventional hybrid structures.
       
  • Characterizing the thermal and mechanical properties and improvement in
           sound insulation performance of magnetite containing nonwovens depending
           on coating conditions
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): İlhan Özen, Hayriye Haskan, Gamze Okyay, Oğuz Demiryürek The scope of this work consists in studying the effects of different processing parameters such as magnetite grinding, magnetite loading amount, type of coating polymer and also sound frequency on the sound insulation property of layered nonwoven structures. Thermal stability and mechanical properties were also investigated. To achieve this goal, nonwoven fabrics were coated with styrene butadiene copolymer latex and ethylene vinyl acetate polymers by using raw and ground magnetite in three different amounts, i.e., 100, 200 and 400 g/m2. Sound transmission loss measurements were performed on the samples using an impedance tube equipped with four microphones. Independent of the coating polymer, addition of magnetite improved thermal stability and mechanical properties. But, sound insulation property was substantially changed depending on the coating polymer. Magnetite incorporation provided noticeable improvements in the ethylene vinyl acetate coated samples (increment values of 3–16 dB), while the effect of magnetite usage was limited in the latex coated samples (0.1–2.9 dB).
       
  • Numerical and experimental tests of steel-concrete composite beam with the
           connector made of top-hat profile
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Piotr Lacki, Jacek Nawrot, Anna Derlatka, Julita Winowiecka The paper presents solution for a steel-concrete composite beam structure. The connectors were executed from sections of a non-weldable top-hat profile 80 × 85 × 3 made of S235 steel. The connectors were fastened to the beam with four shot nails.In the first part of the work the push-out tests of connectors were carried out. The tests allowed to optimize the length of the connector. The connectors with a length of 60 and 100 mm were considered. The results were verified in a numerical analysis.In the second part of the work, for the best variant of the connector, two models of the composite ceiling beam were made: a numerical one and in real scale. The ceiling model was constructed from an IPE I-beam, galvanized trapezoidal sheet, concrete, reinforcing mesh and top-hat connectors. The values of normal stresses and displacements were determined based on the numerical analysis. These results were compared with the displacements obtained in experimental test.The numerical analysis was carried out using the ADINA System program based on the Finite Element Method. The stresses and displacements in the steel and concrete parts as well as cracking in concrete were assessed.
       
  • Prediction of the vacuum assisted resin transfer molding (VARTM) process
           considering the directional permeability of sheared woven fabric
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Jae-In Kim, Yeon-Taek Hwang, Kyung-Hee Choi, Hee-June Kim, Hak-Sung Kim In this study, the in-plane permeability of a woven composite was characterized with respect to the fiber orientation of the deformed woven fabric, to predict the vacuum assisted resin transfer molding (VARTM) process. An analytical model was suggested to predict the permeability of shear-deformed woven fabric and the model was compared to the experiment results. Based on the developed model, the VARTM process for the U-shaped composite structure was simulated using commercial software (Pam-Form and Pam-RTM). The simulation results were compared with that of the VARTM experiment. Considering the fiber directional permeability of the shear-deformed woven fabric, it was concluded that the VARTM simulation could accurately predict the VARTM process results such as the filling time and flow front pattern.
       
  • Deformation behavior of nanoporous gold based composite in compression: A
           finite element analysis
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Jiejie Li, Chenyao Tian, Binbin Lu, Yuehui Xian, Runni Wu, Guoming Hu, Re Xia Integrating a polymer into the nanoporous metals (NPMs) could efficiently reduce the density change during plastic flow with better ductilization, which widens great potential applications of nanocomposites. In this work, a finite element model of stochastic bicontinuous nanoporous structure is generated for the first time. A nanocomposite material is generated by fitting a polymer into the pore space of NPMs, and the mechanical behaviors of the composite of nanoporous gold (npg) and epoxy under uniaxial compression are investigated via finite element analysis. Results show that the stress is mainly concentrated at the ligament necks rather than junctions of the npg constitute phase and the epoxy constitute phase during deformation. In analogy to npg, the Young’s modulus of npg-epoxy composite as a function of metal volume fraction displays a power-law relation and the yield stress has an approximately linear relation. It is worth noticing that the Young’s modulus and the yield stress of nanocomposite exceeds that of each of its constituent phases and are higher than the sum of two pure phases. The present study provides new insights into the mechanical behaviors of npg-epoxy composite, as well as a practical guide for designing a new class of strong and ductile nanocomposites.
       
  • Ultrasonic spectroscopic analysis of impact damage in composites by using
           laser vibrometry
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Daria Derusova, Vladimir Vavilov, Stefano Sfarra, Fabrizio Sarasini, Vladimir Krasnoveikin, Arsenii Chulkov, Sachin Pawar Contemporary composite materials are continuously being modified and improved in accordance with growing quality requirements of aerospace systems. New manufacturing technologies stimulate development of appropriate (novel) nondestructive testing (NDT) methods and respective hardware for detecting and characterizing hidden defects. One of the recent improvements in this area is related to combining acoustic stimulation of test objects and scanning laser vibrometry. This paper describes an ultrasonic spectroscopic approach to laser vibrometry applied to hybrid composite materials subjected to impact damage. The meander-shaped signal for resonance stimulation was applied to enhance the detection of multi-component defects. It has been shown that wide-band frequency stimulation provides some advantages in regard to mono-frequency excitation because it activates more zones of multi-component defects thus allowing more accurate estimation of defect size.
       
  • Damage assessment of carbon-epoxy composites with and without resin flow
           channels
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Kariappa M. Karumbaiah, Christoph Kracke, Mark Battley, Simon Bickerton, Tom Allen The integration of resin flow channels in resin transfer moulding aids manufacturers in numerous ways. They reduce total flow resistance, allowing faster filling, and provide the capability to steer resin flow within a mould. However, the presence of resin flow channels in moulded composites results in local geometric variations affecting fibre alignment. In this work, the static tension and flexural performance of composite laminates with resin flow channel(s) have been investigated. Acoustic emission monitoring was used to characterise damage. The frequency of each distinct damage event was monitored to categorise the damage. Under flexural loads, multiple channel specimens demonstrated damage initiation at lower loads and a high accumulation of AE based damage events when channels were facing the compression side of the bending loads. This study provides insight to the damage mechanism of composites with and without resin flow channels.
       
  • Two-level layup optimization of composite laminate using lamination
           parameters
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Xiaoyang Liu, Carol A. Featherston, David Kennedy This paper provides an efficient method for performing global layup optimization of composite laminates with buckling and manufacturing constraints. The optimization problem is divided into two stages and is based on the use of lamination parameters. During the first stage, exact finite strip analysis and continuous optimum design are employed for buckling optimization of the lamination parameters and laminate thickness. In the second stage, a logic-based procedure combining the branch and bound method with a global layerwise technique is employed to find the optimal stacking sequences to match the optimized lamination parameters obtained in the first stage. In order to ensure the optimized layup can be used in practice, four manufacturing constraints are added into the logical search process, and the feasible region for the lamination parameters with a manufacturing constraint which requires at least 10% of each of four possible ply orientations is studied. By comparing the logic-based method with the use of a genetic algorithm for searching stacking sequences under different requirements, the high efficiency and ability to achieve a global optimal result of the logic-based method are demonstrated.
       
  • Damage mode identification of adhesive composite joints under hygrothermal
           environment using acoustic emission and machine learning
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): D. Xu, P.F. Liu, J.G. Li, Z.P. Chen This paper studies the hygrothermal aging effect on the damage behaviors of adhesive composite joints by acoustic emission (AE) technique. Tensile tests and AE tests are launched for both non-aging and aging specimens under regular and hygrothermal environments, respectively. The clustering analysis, the time-domain analysis and the frequency-domain analysis are combined to identify various damage modes and to study the hygrothermal aging effect of single-lap joint (SLJ). First, the clustering analysis is performed to study the damage mode correlation using four AE characteristic parameters including the time of duration, the peak amplitude, the RA value (the rise time divided by the peak amplitude) and the frequency centroid of gravity. Then, the time-domain analysis is conducted to investigate the hygrothermal effect of the single-lap joint (SLJ). Finally, the frequency spectrum analysis is carried out to study the frequency range for the shear failure of adhesive layer. In addition, the dominant damage mode of SLJ is identified using the wavelet-based decomposition of the ultimate AE signals with the largest energy.
       
  • An accurate and computationally efficient uniaxial phenomenological model
           for steel and fiber reinforced elastomeric bearings
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Nicolò Vaiana, Salvatore Sessa, Francesco Marmo, Luciano Rosati We present a uniaxial phenomenological model to accurately predict the complex hysteretic behavior of bolted steel reinforced elastomeric bearings and unbonded fiber reinforced elastomeric bearings. The proposed model is based on a set of only five parameters, directly associated with the graphical properties of the hysteresis loop, leads to the solution of an algebraic equation for the evaluation of the isolator restoring force, requires only one history variable, and can be easily implemented in a computer program. The proposed model is validated by means of experimental tests and numerical simulations. In particular, the results predicted analytically are compared with some experimental results selected from the literature. Furthermore, numerical accuracy and computational efficiency of the model are assessed by performing nonlinear time history analyses on a single degree of freedom mechanical system and comparing the results with those associated with a modified version of the celebrated Bouc-Wen model.
       
  • Progressive failure of inter-woven carbon-Dyneema fabric reinforced hybrid
           composites
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): M. Cao, Y. Zhao, B.H. Gu, B.Z. Sun, T.E. Tay This study investigates the in-plane mechanical behavior of a twill 2,2 carbon-Dyneema fabric reinforced hybrid composite. A finite element (FE) model of a meso-scale representative volume element (RVE) is developed for simulating the in-plane behavior of the composite. The development of damage in both carbon and Dyneema yarns is modeled through progressive damage models with linear softening laws and the non-linear response of the Dyneema yarn is experimentally determined and described by the Ramberg-Osgood equation. The epoxy resin is regarded as an elasto-plastic material. The damage development in different constituents of the composite is analyzed and correlated with experimental observations. In addition, the role of RVE size in modeling the behavior of the hybrid composite is investigated. It is found that a minimum of size of about five basic units of RVEs is necessary to achieve acceptable predictive results due to shear lag effects.
       
  • Modelling the variability of skin stiffener debonding in post-cured
           top-hat stiffened panels
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): J.E. Yetman, A.J. Sobey, J.I.R. Blake, R.A. Shenoi Glass structures are often used in industries utilising large structural topologies. These structures are typically manufactured by post-curing subcomponents together, using a chopped strand mat layer at the interface. To predict failure of these joints requires an accurate assessment of the material and fracture properties. In this paper two industrially manufactured top-hat stiffened panels are tested to determine the fracture behaviour at the component level. This highlights that the variability seen in fracture properties at coupon level is less evident in structural component response. Then a previously developed set of material properties is used to accurately model the structural response, crack initiation and debonding of the panels under four point bend using Finite Element Analysis which gives final failure at 6.2 kN and a 4.4% error compared to the experimental results which exhibits final failure at 5.94 kN. The specific fracture properties tested and R curve are shown to be critical in assessing crack initiation and propagation with considerable error, 14.5%, provided by data assumed from the literature.
       
  • An analytical-numerical approach to vibration analysis of periodic
           Timoshenko beams
    • Abstract: Publication date: Available online 26 December 2018Source: Composite StructuresAuthor(s): Łukasz Domagalski, Michał Świątek, Jarosław Jędrysiak The subject of this article is analysis of transverse vibrations of beams which geometric and material properties vary periodically along the longitudinal axis. The aim is to present averaged models that take into account the shear deformation and geometric non-linearity, and to analysand transverse vibrations of such beams in moderately large deflection range. As the theoretical foundations, we use Timoshenko beam theory with von Kármán-type non-linearity. This results in obtaining new differential equations with constant coefficients, some of which explicitly depend on the beam inhomogeneity period size. Then, a reasonably simplified model is proposed to describe the vibrations of the considered beams in the low frequency range. The differential equations are transformed into a system of algebraic equations according to the Galerkin method. The response of the beam to transverse harmonic load is investigated by means of a pseudo arc-length continuation scheme. Non-linear coupling between vibration modes and the possibility of superharmonic resonance occurrence are taken into account. As an example of application, few special cases of beam geometry and boundary conditions are examined and compared. The results have the potential application to structural vibration control.
       
  • Damage detection of sandwich panels with truss core based on time domain
           dynamic responses
    • Abstract: Publication date: Available online 26 December 2018Source: Composite StructuresAuthor(s): Lingling Lu, Jie Le, Hongwei Song, Yabo Wang, Chenguang Huang A damage identification method, based on structural time domain dynamic responses and Teager energy operator, is presented for sandwich panels with truss core in the paper. The dimensionless structural dynamic responses, i.e., dimensionless velocity and displacement, are combined to construct damage index. Application of the method on sandwich panels in the cases of single damage and multiple damages with different extents are conducted. Effects of some factors on the method are discussed, including excitation location, excitation frequency, boundary condition, number of points N in Poincare maps. Numerical and experimental results show that the proposed method is effective in detecting both single damage and multiple damages with different extents. Excitation location plays a very important role in affecting the effectiveness of the method. Excitation frequency has little effect on the method, and there is a great selection space of excitation frequencies. Increasing the boundary condition constraint is beneficial for damage identification.
       
  • Dynamic multiscale topology optimization for multi-regional
           micro-structured cellular composites
    • Abstract: Publication date: Available online 25 December 2018Source: Composite StructuresAuthor(s): Jie Gao, Zhen Luo, Hao Li, Peigen Li, Liang Gao In this paper, a new dynamic multiscale topology optimization method for cellular composites with multi-regional material microstructures is proposed to improve the structural performance. Firstly, a free-material distribution optimization method (FMDO) is developed to generate the overall configuration for the discrete element densities distributed within a multi-regional pattern. The macrostructure is divided into several sub regions, and each of them consists of a number of elements but with the same densities. Secondly, a dynamic topology optimization formulation is developed to perform the concurrent design of the macrostructure and material microstructures, subject to the multi-regional distributed element densities. A parametric level set method is employed to optimize the topologies of the macrostructure and material microstructures, with the effective macroscopic properties evaluated by the homogenization. In the numerical implementation, the quasi-static Ritz vector (QSRV) method is incorporated into the finite element analysis so as to reduce the computational cost in numerical analysis, and some kinematical connectors are introduced to make sure the connectivity between adjacent material microstructures. Finally, 2D and 3D numerical examples are tested to demonstrate the effectiveness of the proposed dynamic multiscale topology optimization method for the material-structural composites.
       
  • A Fourier-related FE2 Multiscale Model for Instability Phenomena of Long
           Fiber Reinforced Materials
    • Abstract: Publication date: Available online 24 December 2018Source: Composite StructuresAuthor(s): Rui Xu, Yanchuan Hui, Heng Hu, Qun Huang, Hamid Zahrouni, Tarak Ben Zineb, Michel Potier-Ferry The aim of this work is to develop a computationally efficient multiscale model to accurately simulate and analyze the instability phenomena of long fiber reinforced composites. The multi-level finite element method (FE2), see Feyel 2003, based on the homogenization theory is adopted to realize the real-time interaction between the microscopic and the macroscopic levels. To increase the computational efficiency in the microscopic level and control the nonlinear calculations, the Fourier-related analysis, see Liu et al. 2012, is carried out on the representative volume elements (RVEs), where all fast varying unknowns are replaced by slowly varying unknowns. The established nonlinear multiscale system is solved by the asymptotic numerical method (ANM), see Cochelin 1994, which is more reliable and less time consuming than other classical iterative methods. This model is used to study the instability of the macro structure and the fiber micro buckling of long fiber reinforced composite. The effects of fiber wavelength to the buckling and post-buckling of macro structure are discussed.
       
  • Effects of mechanical properties of adhesive and CFRP on the bond behavior
           in CFRP-strengthened steel structures
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Chuanxi Li, Lu Ke, Jun He, Zhuoyi Chen, Yang Jiao The bond between carbon fiber-reinforced polymer (CFRP) composites and steel is a key issue in CFRP-strengthened steel structures. The determination of key parameters in the bond strength model remains debatable. We studied the bond behavior between CFRP and steel, focusing on the effects of different types of epoxy adhesive and CFRP on the failure modes, bond–slip relationships, and bond strength parameters. The results show that due to the use of various materials, some specimens fail in interface debonding characterized by brittle failure, whereas others have cohesive failure or CFRP delamination characterized by ductile failure. The bond–slip models showed gentle-slope descending branches for interfaces with ductile failure, which is missing in brittle failure. The bond–slip relationships of most specimens can be simplified as bilinear models. However, trilinear models should be used for the specimens failing in the delamination and tearing of CFRP. As for the modes of interface debonding and CFRP superficial delamination, the maximum shear stresses in the interface linearly correlate with the elastic moduli of adhesive. The nonlinear mechanical behavior of interfaces can be well simulated by a cohesive zone model.
       
  • Tailoring of AP-PLY composite laminates for improved performance in the
           presence of delaminations
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Weiling Zheng, Christos Kassapoglou, Longxi Zheng A fibre placement architecture, Advanced Placed Ply (AP-PLY), has been shown to give significantly improved damage tolerance characteristics of composite structures. The behavior of delaminations resulting from low speed impact damage is of particular concern. Emphasis is placed on using developed methodology to expand current knowledge on the delamination response and optimization of simple AP-PLY composite structure. A proposed energy method to analyze the strain energy release rate (SERR) of an existing crack in a composite laminates, was applied to an AP-PLY beam structure. A step by step approach was developed to obtain the SERR of a crack that grows in regions of variable stiffness. The analytical SERR determined when two materials are used in sequence, sets the stage for optimization of AP-PLY composite laminates to tailor stiffness and minimize SERR. The results show promise in providing designs where the stiffness is altered so that delamination growth is delayed.
       
  • An analytical approach to characterize uniaxial in-plane responses of
           commercial hexagonal honeycomb core under large deformations
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): C. Yang, H. Shahverdi Moghaddam, S.R. Keshavanarayana, A.L. Horner In this article, an analytical model is derived to investigate the in-plane homogenized stress-strain relationship of an adhesively bonded commercial hexagonal honeycomb core under large deformation. The model incorporates some advanced features of the core cell such as cell wall curvatures, node bond adhesive layers, and adhesive fillets at the cell wall intersections in the analysis. Nonlinear homogenized results of the fiberglass/phenolic honeycomb core predicted by the analytical model are compared with test data as well as predictions from finite element models (FEMs) of both real and idealized (without modeling the node bond adhesive) core cells to investigate the effects of the node bond adhesive. Predictions of the analytical model are in good agreement with the test data and predictions of the FEM of the real core cell. Homogenized properties of the honeycomb core obtained from the analytical model at infinitesimal strains are compared with several analytical models from the literature. Adhesive peel stress is also calculated by the analytical model and compared with the FEM.
       
  • A frameless picture frame test with embedded sensor: Mitigation of
           imperfections in shear characterization of woven fabrics
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): H. Montazerian, A. Rashidi, M. Hoorfar, A.S. Milani Picture frame test (PFT) is frequently employed for characterizing the shear behavior of woven fabrics. In the present study, the main sources of possible imperfections in the PFT, arising from the operator error during sample installation, to the fixture misalignment and the inherent non-uniformities within the fabric, are reviewed and modeled using the kinematic as well as continuum-based approaches. Upon new understandings from these models, a new test methodology was designed where the shearing frame boundary condition is inscribed on the fabric sample itself during sample preparation; in lieu of fabricating and installing a metallic picture frame. The new frameless picture frame (FPF) test was proven to effectively mitigate the imperfections and provide a simple operation and better control and uniformity of the fabric installation and deformation. Contrary to the conventional PFT, the wrinkling behavior and normalized force response in the FPF was in agreement with the conventional bias extension test, with no close-to-arm fiber bending, while showing a superior test repeatability at both loading and unloading stages. Finally, a mechanically compatible, stretchable sensor was developed and integrated into the fabric samples to monitor and verify the induced local deformation along the yarns under different test methods.
       
  • A novel size-dependent quasi-3D isogeometric beam model for
           two-directional FG microbeams analysis
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Tiantang Yu, Jiankang Zhang, Huifeng Hu, Tinh Quoc Bui A two-directional functionally graded microbeam model is developed for natural frequency and mechanical bending analysis by using NURBS–based isogeometric analysis combined with a non-classical quasi-3D beam theory (NCQ3BT). Material parameters of microbeam continuously and smoothly change along thickness and axial directions. The small size effects are seized with the modified couple stress theory. In the NCQ3BT, both normal and shear deformations are considered without the need for the shear correction factor. The high-order continuity of NURBS directly meets the demand of C1-continuity in the NCQ3BT. Numerical results prove the superior performance and accuracy of the developed approach. The influences of material gradient factors along the axial and thickness directions, material length scale factor, boundary condition, and other aspect ratios of two-directional FG microbeams on mechanical behavior are investigated.
       
  • Synergistic improvement of electrical and thermal conductivities of
           carbon-based nanocomposites and its prediction by Mori-Tanaka scheme with
           interfacial resistances
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Hyung min Kim, Suyeon Lee, Young Seok Song, Doojin Lee Carbon-based nanomaterials have widely been used to enhance the thermal and electrical properties of polymer composites with the aid of miniaturization of electronic devices that require fast heat dissipation and electromagnetic interference shielding at a desired level. A combination of different carbon nanofillers can lead to a strong synergistic effect by creating the electron hopping pathway and conductive network. Here, we fabricate the hybrid nanocomposites composed of two-dimensional graphite nanoplatelets, one-dimensional microscale carbon fibers, and one-dimensional nanoscale multiwalled carbon nanotubes. The synergistic improvement of electrical and thermal conductivities of the hybrid nanocomposites is achieved by a three-dimensional network formation among the microscale and nanoscale fillers. A Mori-Tanaka averaging scheme with perfect and imperfect interfacial resistances under uni-directional and random fiber orientations is presented to predict the synergistic improvement of thermal conductivity of the nanocomposites. A transient temperature response in the nanocomposites is investigated to evaluate heat dissipation capability in which heat transfer rate is enhanced in the case of hybrid nanocomposites. Finite element simulation results are in a good agreement with the transient temperature response experimentally obtained.
       
  • New micromechanics approaches for the effective properties of
           multiferroics composites with spring-type imperfect interfaces
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Yao Koutsawa This study proposed two new micromechanics models to predict the effective properties of multiferroics composites with spring-type imperfect interfaces. The first model is a full field micromechanics scheme based on the mechanics of structure genome, a multiscale constitutive modeling framework, recently discovered to unify the micromechanics and the structural mechanics. The second model is a mean field micromechanics approach that extends the Mori-Tanaka scheme using the concept of the interior and exterior-point Eshelby tensors to multiferroics composites. The imperfect interface model assumes that the normal components of the fluxes (stress, electric displacement and magnetic flux) are continuous across the interface, whereas the potential fields (displacement, electric potential and magnetic potential) suffer interfacial jumps proportional to the normal components of the fluxes. In contrast to multiferroics composites with perfect contact conditions, the effective properties formulations show the dependence on the size of the reinforcements. Numerical examples of fibrous multiferroics composites are used to demonstrate the robustness and accuracy of the proposed micromechanics theories. The size-dependency of the overall properties shows the importance of imperfect interfaces in predicting the effective properties of multiferroics composites.
       
  • Investigation of thermo-elastic buckling of variable stiffness laminated
           composite shells using finite element approach based on higher-order
           theory
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): D. Aditya Narayan, M. Ganapathi, B. Pradyumna, M. Haboussi Here, the thermo-elastic buckling characteristics of variable stiffness composite shells, viz., cylindrical and spherical shell panels, subjected to uniform/non-uniform thermal fields are investigated based on finite element approach introducing higher-order theory accounting through thickness effect. The variable stiffness in the composite laminate is spatially created introducing curvilinear fibers that continuously changes the fiber orientation within the lamina. The critical buckling temperature is evaluated solving the governing equations developed through the principle of minimization of total potential energy by adopting the eigenvalue approach. To select the appropriate structural model, the thermal buckling of such curved panels subjected to thermal fields are initially examined using different structural theories. To predict the buckling temperature, the thermal stress resultants are firstly evaluated using the displacement fields of pre-buckling of the laminated shells under the assumed temperature. The formulation is tested against considering problems for which analytical/numerical solutions available in the literature. A comprehensive study based on various design factors such as curvilinear fiber angular variation, lay-up, length-to- and radius-to-thickness ratios, and boundary conditions on the thermoelastic stability of laminated composite shell panels is made.
       
  • Effects of contact between rough surfaces on the dynamic responses of
           bolted composite joints: Multiscale modeling and numerical simulation
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Zhen Zhang, Yi Xiao, Yuanhong Xie, Zhongqing Su A multiscale numerical model, considering both microscopic interfacial properties and macroscopic composite properties, has been developed to model the dynamic responses of bolted composite structures using the elastic-viscoelastic correspondence principle. The complex contact moduli of the uneven interfaces of the joints, featuring multi-asperity contact at the micro perspective, were derived using the fractal contact theory. The frequency-dependent complex moduli of composite materials were ascertained through modal impact tests on unidirectional composites. The damping and stiffness of the composite specimens were solved within ABAQUS software using the complex eigenvalue method. The damping ratios of the joints decreased by over 8.5% while the resonant frequencies increased by more than 0.59% when the bolts of the joints were adjusted from fully loose to fully tightened. Results from the numerical prediction and the experiment were found to be in good agreement, whereby the influence of the interfacial contact conditions on the dynamic responses of the bolted composite structures was revealed through the multiscale analysis.
       
  • Flexural behavior of basalt fiber-reinforced concrete slab strips
           reinforced with BFRP and GFRP bars
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Karim Attia, Wael Alnahhal, Ahmed Elrefai, Yousef Rihan This research investigates experimentally and analytically a novel one-way slab system reinforced with either basalt fiber-reinforced polymer (BFRP) or glass fiber-reinforced polymer (GFRP) longitudinal bars embedded in fiber-reinforced concrete (FRC) incorporating basalt macro-fibers (BMF). Twelve one-way concrete slab strips were prepared and tested to failure under four-point loading configuration. The investigated parameters included the type of fiber-reinforced polymer bars (BFRP and GFRP), the longitudinal reinforcement ratio ρf (1.4 and 2.8ρbf, where ρbf is the balanced reinforcement ratio), and the volume fraction of the fibers added (0, 0.5, 1, and 2% per volume). The test results demonstrated the promise of BMF to enhance the flexural performance of the tested slab strips in terms of ductility and load-carrying capacities. The formulations of different available codes and design guidelines were used to predict the test results. Comparison between the experimental and predicted results showed the adequacy of the models to predict the flexural performance of the tested slab strips. The findings of this study demonstrated the potential of using the BMF as alternatives to conventional fibers in flexural concrete members.
       
  • Effect of direct service temperature exposure on the bond behavior between
           advanced composites and CMU using NSM and EB techniques
    • Abstract: Publication date: 1 March 2019Source: Composite Structures, Volume 211Author(s): Zuhair Al-Jaberi, John J. Myers, K. Chandrashekhara The durability of fiber reinforced polymer (FRP) and fiber reinforced cementitious matrix (FRCM) for strengthening structural elements has been rather extensively studied in the literature. The influence of directly applying temperature on bond behavior represents an open topic that needs to be considered in more detail. This study is one of the initial studies to investigate the advanced composite bond behavior when subjected to tension force simultaneously with applying temperature. The temperatures considered in this study were at freezing −18 °C (0 °F), ambient 21 °C (70 °F), and high service temperature 49 °C (120 °F), which covers much of the spectrum of structural element service temperatures in the field. The key parameters investigated include different strengthening system under different level of temperature. A total of 36 specimens were subjected to single-lap direct shear simultaneously with applying temperature, and 12 specimens were tested after exposure to the cycles of heating and cooling temperature. The results showed a high reduction of FRP-epoxy bond properties up to 59% when exposed to high service temperatures, while there was insignificant reduction for FRCM bond when subjected to the same temperature.
       
 
 
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