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  Subjects -> ENGINEERING (Total: 2431 journals)
    - CHEMICAL ENGINEERING (210 journals)
    - CIVIL ENGINEERING (203 journals)
    - ELECTRICAL ENGINEERING (112 journals)
    - ENGINEERING (1271 journals)
    - ENGINEERING MECHANICS AND MATERIALS (402 journals)
    - HYDRAULIC ENGINEERING (57 journals)
    - INDUSTRIAL ENGINEERING (77 journals)
    - MECHANICAL ENGINEERING (99 journals)

CIVIL ENGINEERING (203 journals)                  1 2 | Last

Showing 1 - 200 of 203 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: 2)
Advances in Civil Engineering     Open Access   (Followers: 39)
Advances in Structural Engineering     Full-text available via subscription   (Followers: 32)
Agregat     Open Access   (Followers: 1)
Ambiente Construído     Open Access   (Followers: 1)
American Journal of Civil Engineering and Architecture     Open Access   (Followers: 34)
Architectural Engineering     Open Access   (Followers: 5)
Archives of Civil and Mechanical Engineering     Full-text available via subscription   (Followers: 3)
Archives of Civil Engineering     Open Access   (Followers: 12)
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: 6)
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)
Bioinspired Materials     Open Access   (Followers: 5)
Bridge Structures : Assessment, Design and Construction     Hybrid Journal   (Followers: 14)
Building & Management     Open Access   (Followers: 1)
Building and Environment     Hybrid Journal   (Followers: 15)
Building Women     Full-text available via subscription  
Built Environment Project and Asset Management     Hybrid Journal   (Followers: 14)
Bulletin of Pridniprovsk State Academy of Civil Engineering and Architecture     Open Access   (Followers: 6)
Canadian Journal of Civil Engineering     Hybrid Journal   (Followers: 13)
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: 9)
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: 6)
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: 7)
Civil and Environmental Research     Open Access   (Followers: 17)
Civil Engineering = Siviele Ingenieurswese     Full-text available via subscription   (Followers: 4)
Civil Engineering and Architecture     Open Access   (Followers: 22)
Civil Engineering and Environmental Systems     Hybrid Journal   (Followers: 3)
Civil Engineering and Technology     Open Access   (Followers: 12)
Civil Engineering Dimension     Open Access   (Followers: 10)
Civil Engineering Infrastructures Journal     Open Access   (Followers: 1)
Cohesion and Structure     Full-text available via subscription   (Followers: 2)
Composite Structures     Hybrid Journal   (Followers: 284)
Computer-aided Civil and Infrastructure Engineering     Hybrid Journal   (Followers: 11)
Computers & Structures     Hybrid Journal   (Followers: 38)
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: 22)
Construction Science     Open Access   (Followers: 5)
Constructive Approximation     Hybrid Journal  
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: 2)
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: 9)
Fatigue & Fracture of Engineering Materials and Structures     Hybrid Journal   (Followers: 17)
Frontiers in Built Environment     Open Access  
Frontiers of Structural and Civil Engineering     Hybrid Journal   (Followers: 6)
Geomaterials     Open Access   (Followers: 3)
Geosystem Engineering     Hybrid Journal   (Followers: 1)
Geotechnik     Hybrid Journal   (Followers: 3)
Géotechnique Letters     Hybrid Journal   (Followers: 7)
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: 2)
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: 30)
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 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: 8)
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: 1)
Journal of Applied Research in Water and Wastewater     Open Access  
Journal of Bridge Engineering     Full-text available via subscription   (Followers: 14)
Journal of Building Engineering     Hybrid Journal   (Followers: 1)
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  
Journal of Civil Engineering and Construction Technology     Open Access   (Followers: 15)
Journal of Civil Engineering and Management     Open Access   (Followers: 7)
Journal of Civil Engineering and Science     Open Access   (Followers: 9)
Journal of Civil Engineering Research     Open Access   (Followers: 7)
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: 78)
Journal of Composites for Construction     Full-text available via subscription   (Followers: 13)
Journal of Computing in Civil Engineering     Full-text available via subscription   (Followers: 24)
Journal of Construction Engineering     Open Access   (Followers: 9)
Journal of Construction Engineering and Management     Full-text available via subscription   (Followers: 18)
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: 5)
Journal of Materials in Civil Engineering     Full-text available via subscription   (Followers: 8)
Journal of Nondestructive Evaluation     Hybrid Journal   (Followers: 9)
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: 3)
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  
Journal of Structures     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  
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)
Materiales de Construcción     Open Access   (Followers: 1)
Mathematical Modelling in Civil Engineering     Open Access   (Followers: 4)
Media Komunikasi 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)
Photonics and Nanostructures - Fundamentals and Applications     Hybrid Journal   (Followers: 3)
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: 9)
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: 3)
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)
Research in Nondestructive Evaluation     Hybrid Journal   (Followers: 6)
Resilience     Open Access   (Followers: 1)
Revista IBRACON de Estruturas e Materiais     Open Access   (Followers: 1)
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: 10)
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)
Structure and Infrastructure Engineering: Maintenance, Management, Life-Cycle Design and Performance     Hybrid Journal   (Followers: 12)
Structures     Hybrid Journal   (Followers: 1)
Study of Civil Engineering and Architecture     Open Access   (Followers: 10)
Superlattices and Microstructures     Hybrid Journal   (Followers: 2)
Surface Innovations     Hybrid Journal  
Technical Report Civil and Architectural Engineering     Open Access   (Followers: 1)
Teknik     Open Access  
Territorium : Revista Portuguesa de riscos, prevenção e segurança     Open Access  
The IES Journal Part A: Civil & Structural Engineering     Hybrid Journal   (Followers: 6)
The Structural Design of Tall and Special Buildings     Hybrid Journal   (Followers: 5)
Thin Films and Nanostructures     Full-text available via subscription   (Followers: 2)
Thin-Walled Structures     Hybrid Journal   (Followers: 4)
Transactions of the VŠB - Technical University of Ostrava. Construction Series     Open Access   (Followers: 1)
Transportation Geotechnics     Full-text available via subscription   (Followers: 1)
Transportation Infrastructure Geotechnology     Hybrid Journal   (Followers: 8)

        1 2 | Last

Journal Cover
Composite Structures
Journal Prestige (SJR): 1.905
Citation Impact (citeScore): 5
Number of Followers: 284  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0263-8223
Published by Elsevier Homepage  [3162 journals]
  • Sandwich panels under interfacial debonding mechanisms
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Marco Francesco Funari, Fabrizio Greco, Paolo Lonetti The paper presents a nonlinear approach to investigate the behavior of composite sandwich structures with transversely compressible core, under static and dynamic loading conditions. The proposed model, formulated in the 2D framework, incorporates moving mesh cohesive modeling, crack initiation and nucleation at core/skin interfaces. Interface elements are used to predict debonding mechanisms, whereas shear deformable beams and two-dimensional plane stress elements identify skin and core behavior, respectively. In this framework, interfacial crack onset, layer kinematic and debonding propagation effects are correctly simulated. The moving mesh technique, combined with a multilayer formulation, ensures a reduction of the computational costs, required to predict crack onset and progressive evolution of debonding phenomena. Cohesive models for sandwich core/skin interfaces are calibrated by means of comparisons with numerical and experimental data with respect mode I and mode II configurations. Moreover, a parametric study to address the influence of the loading rate and sandwich characteristics on both static and dynamic frameworks is proposed.
       
  • Seismic behavior of glass fiber-reinforced polymer wall panels
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Hao Wu, An Chen, Simon Laflamme Glass fiber-reinforced polymer (GFRP) panels have been increasingly used for structural applications due to their light weight, corrosion resistance and construction-easiness. This study evaluates the seismic performance of GFRP wall panels based on comprehensive shaking table tests and Finite Element Analysis (FEA). A GFRP wall panel is experimentally subjected to harmonic ground motions of frequencies ranging from 10 to 15 Hz. A mass is attached to the top of the panel to simulate gravitational weight. The panel remains undamaged under a peak base acceleration of 2.1 g. Its FEA is conducted using Abaqus based on Rayleigh damping. There is a good correlation between the experimental and FEA results. Another FEA model is developed to study the seismic behavior of a Reinforced Concrete (RC) wall, which is validated by results from an existing study. The two FEA models are then used to compare the seismic performance of GFRP wall panels versus RC walls in terms of drift ratio and hysteretic behavior. It is found that while GFRP wall panels cannot replace RC walls in multi-story buildings due to their low stiffness, their performances are comparable to RC walls for low-rise buildings. Therefore, GFRP wall panels can be potentially used in low-rise buildings in seismic regions.
       
  • Deformation behavior of sandwich hemispherical structure under axial
           compression at low temperature
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Ji He, Shuhui Li, Shanshuai Wang Foam core sandwich structure has excellent insulation and specific strength and is widely used in the aerospace, aviation, navigation and military fields. The hemispherical shell of this kind sandwich structure is often used as energy and load carrying component due to its energy absorption ability. Some foam core sandwich hemispherical structures work in particular ultra-low temperature environments which undergo both temperature and mechanical loads. The research on the load carrying capacity of such structures in ultra-low temperature environment is essential for design and verify its properties. In this paper, the low-temperature mechanical properties of the face sheet and core materials were tested. The thermo-mechanical coupling numerical model was established and verified by comparison with the experimental results. Through the numerical simulation, the compressive behavior of the foam core hemispherical shells with different sizes was obtained under three different low-temperature loading situations. The effect of temperature loading on the deformation mode, load carrying capacity and deformation accumulation is further studied. It is suggested that the cooling of the out sheet is a relatively preferred low-temperature loading method. It also provides advice and ideas for the use of such structures.
       
  • Analysis of effective elastic properties for shell with complex
           geometrical shapes
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): D. Guinovart-Sanjuán, K. Vajravelu, R. Rodríguez-Ramos, R. Guinovart-Díaz, J. Bravo-Castillero, F. Lebon, F.J. Sabina The manuscript offers a methodology to solve the local problem derived from the homogenization technique, considering composite materials with generalized periodicity and imperfect spring contact at the interface. The general expressions of the local problem for an anisotropic composite with perfect and imperfect contact at the interface are derived. The analytical solutions of the local problems are obtained by solving a system of partial differential equations. In order to validate the model, the effective properties of the structure presented in the literature are obtained as particular cases. The solution of the local problem is used to extend the study to more complex structures, such as, wavy laminates shell composites with imperfect spring type contact at the interface. Also, the results are compared with the results for perfect and imperfect contact models available in the literature.
       
  • Dynamic stability of sandwich functionally graded micro-beam based on the
           nonlocal strain gradient theory with thermal effect
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Mohammed Al-shujairi, Çağrı Mollamahmutoğlu In this study, the dynamic stability of functionally graded (FG) size dependent sandwich micro-beam subjected to parametric axial excitation with different boundary conditions including thermal effects is investigated. Based on the nonlocal strain gradient theory (NLSGT) in conjunction with the first order shear deformation beam theory (FSDBT) and Hamilton's principle, governing equations of motion and corresponding boundary conditions were obtained. Differential quadrature (DQ) method is utilized to solve the derived differential equations. Material properties of the FG part of sandwich micro-beam are varied through the thickness of the beam by assuming the classical rule of mixture. Effects of the slenderness ratio (L/h), nonlocal parameter (ea), FG mixture index (k), length scale parameter (lm), static load factor (ηs), temperature change, various boundary (C-C), (S-S), (C-S) conditions and different cross-section shapes on the dynamic stability behavior of the sandwich micro-beam are investigated. Numerical solution for determining the parametric instability regions of a FG sandwich micro-beam under different boundary conditions and various effects are the original contributions of this study.
       
  • Dynamic stability of doubly-curved multilayered shells subjected to
           arbitrarily oriented angular velocities: Numerical evaluation of the
           critical speed
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Francesco Tornabene, Michele Bacciocchi The paper is focused on the evaluation of the critical speed of rotating doubly-curved multilayered shell structures. The theoretical framework developed to this aim is based on a general formulation capable to define several Higher-order Shear Deformation Theories (HSDTs) in a unified manner. The current approach can deal easily with angular velocities applied about a generic axis of the structure. This aspect represents a clear advancement with respect to the formulations available in the literature, which are developed mainly to investigate the dynamic behavior of rotating shells of revolution (disks, circular cylinders and conical shells), in which the angular velocity is applied about their revolution axis. It is important to underline that the effects of both Coriolis and centripetal accelerations on the dynamic response of shell structures, characterized by various geometric shapes, are included in the model. The quadratic eigenvalue problem that lies behind the free vibration analysis in hand is solved numerically by means of the well-known Generalized Differential Quadrature (GDQ) method. The critical speed is obtained as a result of many parametric investigations, which are defined for increasing values of the applied angular velocities. Finally, it should be mentioned that the current research falls within the aim of the study of the dynamic stability of rotating structures. For this purpose, several considerations concerning the flutter and divergence phenomena are presented.
       
  • Experimental investigation of the effect of defects in Automated Fibre
           Placement produced composite laminates
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Wilhelm Woigk, Stephen R. Hallett, Mike I. Jones, Moritz Kuhtz, Andreas Hornig, Maik Gude Automated composite manufacturing processes such as Automated Tape Laying (ATL) and Automated Fibre Placement (AFP) are effective methods to produce high quality, lightweight parts. Typically, preimpregnated fibres or tapes are laid side-by-side onto a tooling surface to generate the composite preform. Although these two main technologies are widely used to produce large composite components, inconsistencies such as overlapping tapes or gaps between adjacent tapes may occur during the manufacturing. Within this study, the effect of gaps and overlaps, so-called defects, has been investigated experimentally. Tensile and compressive testing has been carried out on specimens with a quasi-isotropic, symmetric layup into which artificial defects in various defined formations were introduced. Of particular interest were the strength knockdown factors and changes in the failure mode.
       
  • The coupling mechanism and damage prediction of carbon fiber/epoxy
           composites exposed to lightning current
    • Abstract: Publication date: Available online 12 July 2018Source: Composite StructuresAuthor(s): H. Chen, F.S. Wang, X.T. Ma, Z.F. Yue Numerical implementation of carbon fiber/epoxy composites exposed to simulated lightning current is presented in order to elucidate coupling mechanism and damage prediction caused by a lightning strike. In order to accurately simulate lightning load, the coupling simulation of lightning electromagnetic fluid and composite plate is used to study lightning damage. Multivariate interpolation scheme for coupling procedure is necessary to transfer information of fluid-solid coupling interface. A complete set of computational models are established that contains magneto hydro dynamic (MHD) model, Structural finite element (FE) model and the corresponding interpolation procedure for non-matching mesh points. Different radial basis methods are discussed for interpolation scheme, which show that volume spline function has an advantage in terms of precision and efficiency for mesh points in this paper. Based on numerical results, damage mechanism of carbon fiber/epoxy composites is revealed and temperature dependency of electrical/thermal material parameters is assumed. According to numerical results of carbon fiber/epoxy composites and thermal decomposition behavior, the damage area and depth estimated from numerical results are predicted.
       
  • Integration of Material and Process Modelling in a Business Decision
           Support System: Case of COMPOSELECTOR H2020 Project
    • Abstract: Publication date: Available online 12 July 2018Source: Composite StructuresAuthor(s): Salim Belouettar, Carlos Kavka, Borek Patzak, Hein Koelman, Gast. Rauchs, Gaetano Giunta, Angela Madeo, Sabrina Pricl, Ali Daouadji This paper shares and contributes to a ground-breaking vision developed and being implemented which consists in the integration of materials modelling methodologies and knowledge-based systems with business process for decision making. The proposed concept moves towards a new paradigm of material and process selection and design by developing and implementing an integrated multi-disciplinary, multi-model and multi-field approach together with its software tool implementation for an accurate, reliable, efficient and cost effective prediction, design, fabrication, Life Cycle Engineering (LCE), cost analysis and decision making. This new paradigm of integrated material design is indeed endowed with a great potential by providing further insights that will promote further innovations on a broad scale.
       
  • Micromechanical modeling of water-induced interfacial failure of ramie
           fiber reinforced thermoplastic composites
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Jianxia Yang, Yitong Guo, Lan Yao, Yiping Qiu This paper proposed a micromechanical model to describe water-induced interfacial failure of natural plant fiber reinforced composites. The model was built with the consideration of fiber swelling, thick-wall cylinder deformation and analysis of shear-lag effect. Debonding tests and scanning electron microscope tests of ramie fiber/polypropylene micro-composites conditioned in environments with different water content were done to verify the model. The results showed that in the environment with 65% relative humidity (RH), the water-induced interfacial shear stress was predicted to be 1.51 MPa, much lower than the interfacial shear strength (IFSS) of dry micro-composites (19.67 MPa) and the interface was not damaged. In liquid water, a water-induced interfacial shear stress of 20.02 MPa was predicted, larger than 19.67 MPa and the interfacial adhesion was damaged solely by water absorption. At 90% RH, however, the predicted water-induced interfacial shear stress was only 5.32 MPa but premature debonding already occurred, which could be due to the matrix creep creating radial debonding.
       
  • Intelligent 3D data extraction method for deformation analysis of
           composite structures
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Xiangyang Xu, Hao Yang, Yi Zhang, Ingo Neumann Nowadays, with the development of demand for construction, the use of composite structures in architectures become more and more popularity. How to improve the intelligent level of deformation monitoring has become one of the key problems. A detailed understanding about deformation behavior is significant for better monitoring of structures, especially in terms of accuracy and detail. The innovation of this paper focuses on that terrestrial laser scanning (TLS) measurement is adopted to investigate deformation of the composite masonry structures.In this paper, deformation segmentation and analysis of the masonry structures are investigated and the deformation tendency is compared and analyzed, based on the intelligent data extraction by window selection method, where high precision 3D laser technology provides reliable experimental data for this research. The deformation of different surfaces of a composite arch is considered and the maximum displacement distribution is analyzed through partially comparing the deformation of different epoch data.
       
  • Experimental study of the deformation of a ballistic helmet impacted with
           pistol ammunition
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): A. Miranda-Vicario, P.M. Bravo, F. Coghe Currently, ballistic helmets are mostly designed to stop fragments from diverse explosive devices. Nowadays, new requirements have emerged for helmets, such as stopping direct impacts from revolver and pistol threats. The probability of these types of impacts on helmet systems is increasing due to the changes in warfare and military operations. Although, it is possible to stop this kind of projectile, there is a lack of studies regarding the possible injuries suffered by the user due to non-perforating impacts.In this research, a comparison between the results obtained with a clay head form and a head surrogate with force sensors was done to estimate the load force on the skull during an impact. 9 × 19 mm FMJ projectiles were fired against a ballistic helmet to study the indentation and the force generated by the back face deformation against the two different head forms.
       
  • Flexural behavior of full-scale circular concrete members reinforced with
           basalt FRP bars and spirals: Tests and theoretical studies
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Salaheldin Mousa, Hamdy M. Mohamed, Brahim Benmokrane, Emmanuel Ferrier This paper reports on the experimental results of flexural tests on full-scale circular reinforced concrete members with a total length of 6000 mm and diameter of 500 mm reinforced with Basalt Fiber-Reinforced-Polymer (BFRP) reinforcement, followed by an intensive analytical study and finite-element analysis. The main investigated parameters were the ratio and type of longitudinal reinforcement. A steel-reinforced concrete specimen was fabricated as a reference. Test results show that the deformability of the tested circular BFRP-RC members significantly exceeded the limitations in North American codes. Moreover, the nominal flexural strength of one BFRP-RC specimen was almost two times that of its steel-reinforced counterpart with the same reinforcement ratio. The analytical model presented herein using a layer-by-layer analysis was capable of predicting the flexural strength of the circular BFRP-RC members. In addition, a non-iterative analysis method including simple design equations are presented. This method accurately and simply predicted the flexural capacity and can be considered a simple and more straightforward method for practicing engineers. In addition, the finite-element model developed predicted the response of the tested specimens with a reasonable degree of accuracy and was used to extend the range of the investigated parameters.
       
  • Influence of micro-scale uncertainties on the reliability of fibre-matrix
           composites
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Sadik L. Omairey, Peter D. Dunning, Srinivas Sriramula This study investigates the effect of micro-scale geometric and material property uncertainties on the elastic properties and reliability of fibre reinforced composite materials. Composite materials are often designed using conservative design factors to account for a limited understanding of how multi-scale uncertainties effect reliability. Structural reliability analysis can produce more efficient designs, but requires an understanding of how all sources uncertainty effect probability of failure. Previous studies have not considered micro-scale geometrical uncertainties and their combinations in a multi-scale probabilistic-based reliability framework. Thus, this study will investigate the effect of numerous combinations of micro-scale material property and geometric uncertainties on the homogenised elastic properties. Furthermore, to account for the effect in a reliability-based framework, a novel surrogate modelling technique is developed to represent the uncertainties efficiently. The study concluded that the geometrical fibre stacking uncertainty is as influential as the widely investigated constituent material stiffness uncertainties. Consequently, representing the micro-scale geometric uncertainties within the developed multi-scale probabilistic-based framework improves the estimated stiffness. Thus probability of failure is reduced, compared with considering material property uncertainties only. Moreover, the framework clarified and highlighted the importance of representing fibre geometrical stacking uncertainty for a deeper understanding of their effect on composite stiffness properties.
       
  • Construction of statistically similar representative volume elements for
           discontinuous fiber composites
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Takashi Sasagawa, Masato Tanaka, Ryuji Omote, Daniel Balzani A computational method is proposed for the construction of statistically similar representative volume elements (SSRVEs) for discontinuous fiber composites (DFCs) in order to enable an efficient calculation of material properties based on computational homogenization. The SSRVEs are obtained by solving an optimization problem which minimizes the difference between the power spectral density of a target microstructure and its simplified one. The SSRVEs are constructed for target microstructures serving as examples for DFCs, which are validated by means of comparing the mechanical properties of the target microstructures with the ones of the SSRVEs. The results show that the mechanical properties of the SSRVEs agree with the target microstructures and that the SSRVEs can extremely reduce the computational costs of finite element analyses to derive macroscopic material properties of DFCs.
       
  • Integration of carbon nanotube sensing skins and carbon fiber composites
           for monitoring and structural repair of fatigue cracked metal structures
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Shafique Ahmed, Erik T. Thostenson, Thomas Schumacher, Sagar M. Doshi, Jennifer R. McConnell Advanced composite materials have been investigated for repair of fatigue-damaged metal structures, but one of the challenges is the repair often covers-up underlying damage, preventing visual inspection. A novel approach where a carbon nanotube-based sensing layer integrated in a steel/composite adhesive bond has been investigated as an approach for repair while adding capability to detect the adhesive bond integrity and monitor propagation of cracks in the underlying substrate. The sensing layer, composed of a random mat of aramid fibers coated with carbon nanotubes, offers tremendous application flexibility for integration of sensing capabilities in structures. Experiments examining fatigue crack propagation in structural steel with a composite repair and integrated bondline sensing increased the fatigue life by 380% to over 500%, depending on configuration. The sensing layer was able to monitor deformation and crack propagation in real-time and shows potential for use in periodic inspection-based monitoring of cracks using electrical property changes.
       
  • Numerical study of composite fragment impacts onto rigid target
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): J. López-Puente, A. Mata-Díaz, J. Pernas-Sánchez, J.A. Artero-Guerrero, D. Varas In this work, it is proposed a numerical methodology to model the behaviour of composite laminates when they act as impactors at high velocity. The numerical model uses an intralaminar criterion based in the Hashin model and a Progressive Damage model to describe the ply behaviour, whereas the interlaminar failure is taken into account by means of cohesive interactions. The validation of the model is performed attending the kinematics and erosion of the laminate during the impact process onto a rigid target as well as the force and impulse generated. Once validated, the model is used to analyse the influence of the fragment miss-alignment in the impact process.
       
  • Damage identification for plate-like structures using ultrasonic guided
           wave based on improved MUSIC method
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Hao Zuo, Zhibo Yang, Caibin Xu, Shaohua Tian, Xuefeng Chen The ultrasonic guided wave has emerged as one of the most prominent and promising tools for metal and composite structures in the fields of structural health monitoring (SHM) and nondestructive testing (NDT). This paper presents a novel model-based 2D multiple signal classification (MUSIC) damage identification algorithm for plate-like structures. Unlike the conventional MUSIC algorithm, the proposed model-based 2D MUSIC damage identification algorithm is deduced based on the assumption of near-field according to the propagation model of guided waves. Since scattered signals contain the location information of damage, the cross-correlation function of residual signals received by experiment and scattered signals received by damage scattering model are developed for spatial spectrum estimation MUSIC algorithm. Due to the uncorrelation of signal and noise, the damage can be successfully identified by searching the peak point of spatial spectrum in the monitored area employing the orthogonality of signal subspace and noise subspace. The accuracy and effectiveness of the proposed method are firstly validated by numerical simulation on aluminum plate, and the general applicability is further verified by experiments for the damage identification of laminated composite plate. The numerical and experimental results demonstrate the proposed damage identification algorithm is appropriate for damage identification of plate-like structures with high estimation accuracy and resolution.
       
  • A novel univariate method for mixed reliability evaluation of composite
           laminate with random and interval parameters
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Xiao Li, Zheng Lv, Zhiping Qiu Requiring probability density distribution functions of uncertain variables, it is difficult for conventional structural reliability analysis methods to calculate the reliability of composite laminates with both random and interval variables. To evaluate the safety of composite laminated structures under this circumstance, this paper is aimed at developing a precise and efficient univariate method for the reliability assessment of composite laminates taking use of Legendre orthogonal polynomials and Monte Carlo Simulation. In this paper, based on the Tsai-Wu failure criterion and first-ply failure assumption, the failure criterion of composite laminate is constructed firstly. Then the performance function of each lamina is approximately expressed as the sum of univariate contributions of all uncertain variables on the basis of the univariate method. Taking use of Legendre orthogonal polynomials, the univariate functions of random and interval variables are constructed by the least square fitting method and the univariate contribution bounds of interval variables are derived afterwards. Furthermore, the interval of failure probability can be calculated by substituting contribution bounds of interval variables and sample points of random variables into univariate function. At last, two examples and an engineering application are provided to demonstrate the efficiency and accuracy of the proposed method.
       
  • Experimental and simulation investigation of the reversible bi-directional
           twisting response of tetra-chiral cylindrical shells
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Chao Ma, Hongshuai Lei, Jian Hua, Yingchun Bai, Jun Liang, Daining Fang Chiral-type cells consisting of rigid nodes and rotatable ligaments provide an opportunity to develop lightweight engineering structures with unique mechanical performances. For a 2D or 3D chiral-type cellular structure system with a periodic arrangement of chiral cells, a distinct rotational response will present because of the asymmetrical and geometrical configuration. In this article, a tetra-chiral cylindrical shell is proposed on the basis of natural plant architecture. This shell exhibits a reversible bi-directional twisting deformation in the axial compression and tension processes. A theoretical model is proposed via the geometrical parameters of cells to describe the relationship between twist angle and axial displacement. Two categories of tetra-chiral cylindrical shell specimens are fabricated utilizing additive manufacturing technique involving the application of nylon and AlSi10Mg materials. Uniaxial compressive tests and finite element simulation are conducted to reveal the twist deformation mechanism. Results verify that the twist characteristics of the chiral-type shell, which are adjustable in terms of the rotational direction and angle, are only related to the distribution and geometrical sizes of ligaments. The innovative chiral-type cylindrical shell provide a new design strategy which can be used in engineering applications as compress- or stretch-twist coupled smart actuators, biomechanical devices, and micro sensors.
       
  • Paperboard tubes failure due to lateral compression-experimental and
           numerical study
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Leszek Czechowski, Maria Bieńkowska, Włodzimierz Szewczyk The work provides an analysis of paperboard tubes subjected to transversal compression force. The investigations were performed for 8 tubes of different radii and different wall thicknesses. The number of layers for detailed pipe ranged from 4 up to 13. The each layer of the paper was modelled with orthotropic material properties. To compare the obtained results of experimental tests, numerical simulations of considered tubes in Ansys 16.2® software were conducted. The calculations were carried out for total failure of pipes using the anisotropic Hill potential theory to implement progressive phase of damage. The scores of investigations were compared with each other and discussed.
       
  • Elastic dependence of particle-reinforced composites on anisotropic
           particle geometries and reinforced/weak interphase microstructures at
           nano- and micro-scales
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Wenxiang Xu, Yang Wu, Mingkun Jia This contribution sheds light on the coupled effects of anisotropic particle geometries (i.e., shape and size) and reinforced/weak interphase characteristics (i.e., volume fraction, thickness, moduli and Poisson ratio) on the elastic properties of particle-reinforced composites (PRCs) at nano- and micro-scales. A powerful micromechanics approach that incorporates interphase microstructures into the average-field theory is used to predict the effective elastic modulus, Poisson ratio, shear modulus and bulk modulus of three-phase PRCs including spheroidal nano-/micro-particles, reinforced/weak interphase and matrix. Comparison with measurements indicates this optimized model is a reliable means to evaluate the elastic properties of three-phase PRCs at nano- and micro-scales. Plus, the results show that the elastic response of PRCs strongly depends on the coupled effects of the aspect ratio and geometrical size factor of spheroidal nano-/micro-particles and the volume fraction of reinforced/weak interphase, suggesting that the properties of such materials can be tailored via proper composite engineering and design.
       
  • Morphology, static and fatigue behavior of a natural UD composite: The
           date palm petiole ‘wood’
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): R. Benzidane, Z. Sereir, M.L. Bennegadi, P. Doumalin, C. Poilâne Large quantity of date palm wastes annually accumulate in Algeria. We investigate date palm petiole wood (DPPW) and macroscopic fibers from northern and southern Algeria by X-ray tomography, monotonic tension and compression, microscopy analysis, and fatigue tensile tests. DPPW is a unidirectional composite (VF=25%,ρ=210kgm-3) consisting of a fibrovascular ultrastructure (reinforcement) and parenchyma (matrix). Mechanical properties of southern DPPW (E=0.5GPa,σu=6MPa,εu=1.75%) are higher than northern ones because of the dry climatic conditions, its density also is higher. Main failure modes are cell-wall tearing and spheroidal-cell detachment (parenchyma), and pull-out or net fracture (fibers). Stress ratio is the major fatigue parameter, R=0.125 is a limit of endurance for transverse southern DPPW. High mechanical homogeneity of DPPW along that direction reduces the risk for damage development. Thanks to limited density, high fatigue life, and neglectable cost, DPPW is a good candidate for local development of sandwich core.
       
  • Numerical modelling of partially potted inserts in honeycomb sandwich
           panels under pull-out loading
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Ralf Seemann, Dieter Krause Sandwich panel inserts are prone to pull-out loading, while predicting the pull-out strength is challenging due to the multitude of damage mechanisms involved. The present paper describes the implementation of two state-of-the art non-linear finite element models for predicting the pull-out strength. The two models include a 3D-continuum model where the core was modelled using 8-node brick elements with a homogenized material model and a detailed meso scale model with accurate honeycomb cell representation using 4-node shell elements. The simulation results are benchmarked against experimental data of the reference configuration. Both models enable to predict the strength accurately, while the 3D-continuum model can be considered favourable for most applications due to the reduced computational effort.
       
  • Simplified stress analysis of functionally graded single-lap joints
           subjected to combined thermal and mechanical loads
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Eric Paroissien, Lucas F.M. da Silva, Frédéric Lachaud Functionally graded adhesive (FGA) joints involve a continuous variation of the adhesive properties along the overlap allowing for the homogenization of the stress distribution and load transfer, in order to increase the joint strength. The use of FGA joints made of dissimilar adherends under combined mechanical and thermal loads could then be an attractive solution. This paper aims at presenting a 1D-bar and a 1D-beam simplified stress analyses of such multimaterial joints, in order to predict the adhesive stress distribution along the overlap, as a function of the adhesive graduation. The graduation of the adhesive properties leads to differential equations which coefficients can vary the overlap length. For the 1D-bar analyses, two different resolution schemes are employed. The first one makes use of Taylor expansion power series (TEPS) as already published under pure mechanical load. The second one is based on the macro-element (ME) technique. For the 1D-beam analysis, the solution is only based on the ME technique. A comparative study against balanced and unbalanced joint configurations under pure mechanical and/or thermal loads involving constant or graduated adhesive properties are provided to assess the presented stress analyses. The mathematical description of the analyses is provided.
       
  • Assessment of uncertainty in damage evaluation by ultrasonic testing of
           composite structures
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Angelika Wronkowicz, Krzysztof Dragan, Krzysztof Lis Ultrasonic testing (UT) is a commonly used non-destructive testing method of composite materials. UT enables determining a geometry of internal damage, its surface area and depth location. However, measurement uncertainty should be taken into consideration when interpreting UT results, which follows from various factors including the test material parameters and selection of the operating parameters, such as the scanning method and applied transducer’s characteristics. Moreover, uncertainty in the flaw size assessment is caused by signal or image processing methods applied to the obtained ultrasonic scans, which may return incorrect results. The article presents an overview of factors influencing on the measurement uncertainty depending on variable UT parameters, with reference to appropriate standards, as well as post-processing of the obtained scans. The experimental studies aimed at investigation on the measurement errors were performed on composite specimens made of CFRP with flat-bottom holes of various diameters using the Pulse-Echo and the Phased Array UT methods.
       
  • Time-dependent damage analysis for viscoelastic-viscoplastic structural
           laminates under biaxial loading
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Thomas Berton, Sandip Haldar, John Montesano, Chandra Veer Singh Many composite structures are required to sustain severe thermo-mechanical loads over extended periods of time, during which viscoelastic and viscoplastic behavior can cause the progression of micro-damage. In this paper, a new computational multi-scale model that couples micro-damage mechanics with Schapery’s theory of viscoelasticity and viscoplasticity has been developed to predict time-dependent damage evolution in laminates under constant biaxial loading. After validation with experimental data, the new model capabilities are showcased by predicting damage evolution in two distinct laminates under different axial and transverse loads over time. It is found that damage evolution in both laminates is highly sensitive to the biaxial loading levels, and that crack multiplication in each ply is dependent on stacking sequence and ply orientation. The developed multi-scale model may be a suitable design tool for composite structures required to endure long-term loads in demanding environments.
       
  • Finite element analysis of initial imperfection effects on kinking failure
           of unidirectional glass fiber-reinforced polymer composites
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Wei Sun, Anastasios P. Vassilopoulos, Thomas Keller The compressive kinking behavior of non-slender unidirectional glass fiber-reinforced polymer (GFRP) specimens has been analyzed by finite element (FE) models. The experimentally observed imperfections, including the initial fiber waviness throughout the entire specimen volume and the scattered resin/interface defects, were taken into account in the FE models. The birth-and-death method was employed to simulate the progressive damage to the material. The consideration of the coexistence of initial fiber waviness and initial resin/interface defects was found to be essential for accurate modeling of the kinking failure process. Kinking was initiated due to the disproportional increase of the fiber microbuckling at the locations of initial defects. The numerically obtained peak load, fiber microbuckling amplitudes, kink band angle and width, and compressive strain concentrations at the kink band edges were well predicted compared to the experimental results. The number of defects was less significant than the fact that defects existed that served as initiation points of the kink band formation.
       
  • Development of work-hardening performance in stainless-steel cylindrical
           columns by application of CFRP jackets
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): A.R. Nazari, M.Z. Kabir, H. Hosseini-Toudeshky Recent researches indicated advantageous characteristics for the metallic structural components, strengthened by FRP materials. The current paper examines the load carrying capacity and energy absorption of strengthening stainless-steel cylindrical columns using CFRP jackets. In the experimental program, the circumferentially over-wrapped columns showed considerable development in the work-hardening performance in addition to its maximum load carrying capacity. In the succeeding, a numerical simulation using the FE method was implemented for the further parametric studies. The validation of numerical modeling was primarily carried out with the experimental results. Subsequently, the influence of various lay-up configurations of the FRP jackets was investigated on the response of the strengthened columns. Furthermore, the failure mechanism based on damage criteria in FRP jacket and stainless steel column was studied in details. The main theme of the current work is focused on the interactive mechanical behavior of the metallic column and the composite jacket in the post yield of the nonlinear domain of the stainless-steel column. The results showed the promising influence of the CFRP-strengthening procedure on stainless-steel cylindrical columns under axial compression.
       
  • Spatiotemporal characterization of 3D fracture behavior of
           carbon-fiber-reinforced polymer composites
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Shenli Pei, Kaifeng Wang, Yang Li, Danielle Zeng, Xuming Su, Jingjing Li, Hui Yang, Xianghui Xiao This study proposed a spatiotemporal algorithm to quantitatively characterize the in-situ 3D fracture behavior of carbon-fiber-reinforced polymer (CFRP) composites at microscale. In-situ micro X-ray computed tomography (µXCT) integrated with a tensile stage was applied to capture the 3D fracture evolution of the CFRP composites, where the initiation and propagation of fracture features (e.g., fiber tip-end crack and fiber/matrix debonding) were identified. After the reconstruction of the 3D material microstructure, the proposed spatiotemporal algorithm thereafter extracted the fracture features by employing multiple image processing techniques for quantitative analysis. A similar distribution of the 3D strain obtained from the volumetric digital image correlation demonstrated the feasibility of the developed spatiotemporal algorithm. Moreover, this algorithm provided in-depth and quantitative analysis of fracture features, which provided insights into the microscale failure mechanism and thus shed light on the improvement of failure criteria for CFRP composites with complex microstructures.
       
  • Hysteretic friction behavior of aluminum foam/polyurethane
           interpenetrating phase composites
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Shaobo Liu, Aiqun Li In this study, the hysteretic friction behavior of aluminum foam/polyurethane interpenetrating phase composites (AF/PU composites) was experimentally investigated by different pre-compression, loading frequency and displacement amplitude. To describe this hysteretic response, the Bouc-Wen model was modified by introducing the accumulated stiffness, which was affected by the displacement amplitude. The maximum force, stiffness and damping ratio were measured in load-displacement hysteretic curves to evaluate the multi-phased hysteretic friction behavior. The experimental results illustrate that the hysteretic friction behavior is divided into three phases by the loading amplitude and is independent of the loading frequency, but the transition in each phase is greatly influenced by the enhanced pre-compression. The modified Bouc-Wen model is found to adequately capture the hysteretic friction response by comparisons with experimental data. All of the results demonstrate that the AF/PU composites have a good potential applied in friction dampers for improving the seismic performance of structures under the ground motion with different intensities.
       
  • Measuring the negative pressure during processing of advanced composites
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Navid Zobeiry, Caitlin Duffner Pre-impregnated sheets of advanced carbon fibers with highly viscous thermoset-based resin systems are commonly used in fabricating aerospace composite parts. As prepreg sheets are vacuum bagged and heated during processing, the resin slowly infiltrates in dry spots between fibers. Under vacuum condition, surface tension-induced capillary effects impose deep negative pressures on the liquid resin, leading to tensile stretching. A method is presented to quantify the capillary-induced negative pressure. During processing, samples are quenched to freeze the infiltration process before taking SEM images. Using image analysis and by invoking interfacial stress boundary condition, the pressure distribution is determined. Sub-micron radii of curvature at the resin interface were measured corresponding to local negative pressures up to several atmospheres and an average pressure of −10 to −50 kPa. Effects of negative pressures on the state of material and on defects such as resin phase separation are discussed.
       
  • Meshing recommendations for the P-approach application in ABAQUS – A
           tool for pheno-numerical spring-in prediction
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): Erik Kappel A numerical study is performed which analyzes the effect of mesh parameter settings on the prediction accuracy of the P-approach, a simulation concept which has been proposed earlier by the author for predicting process-induced distortion of composite structures. A parameterized solid-element finite element (FE) ABAQUS model of a composite L-profile is used as the reference geometry, while numerically predicted distortions are compared with nominal values. This paper shows that significant, unacceptable mesh-related deviations occur for some mesh-parameter configurations. The paper also shows that the main drivers of these deviations are related to the effective geometry of the finite elements at the L-profile’s bend.Based on this finding, the P-approach has been extended with a novel model formulation, which helps to minimize mesh-related deviations, especially for coarse meshes. The validity of the proposed model is verified by a re-execution of the full study, which shows a remarkable reduction of mesh-related deviations. The paper provides general mesh-parameter guidelines for the P-approach application in ABAQUS as well as measures to apply coarser meshes without losing prediction accuracy.
       
  • Energy absorption study considering crush test on carbon fiber/epoxy and
           carbon fiber/polyurethane structural composite beams
    • Abstract: Publication date: 1 November 2018Source: Composite Structures, Volume 203Author(s): R.M. Di Benedetto, B.Z. (Gama) Haque, M.A. Ali, J. Tierney, D. Heider Crashworthiness of a high-performance composite structure is associated to its energy absorption capacity through controlled failure mechanisms during an impact or crushing event. Furthermore, crush and compression testing usually characterize the failure mechanisms, which considers the specimen geometry, material type, fiber architecture and loading rate. This study focuses on energy absorption capability of carbon fiber/epoxy (CF/Epoxy) and carbon fiber/polyurethane (CF/PU) composite hat beams (HB) by a nonstandard quasi-static crush test for crashworthiness applications, including a discussion of how the material properties affect the structural behavior. In addition, the materials evaluation by low velocity impact (LVI), compression after impact (CAI) test, and in-plane shear response by tensile test was performed to determine and compare mechanical behavior and damage modes caused by the impact event. Despite the differences observed on the CF/Epoxy and CF/PU composites in terms of energy absorption capacity on impact, post-impact compression strength and shear strength, the HB specimens presented similar average crush force when subjected to the crush loading, but different types of failure modes. A multiple linear regression model has been developed which is able to predict the HB absorbed energy on crush considering the matrix behavior and energy absorption capability corresponding the failure mechanisms observed.
       
  • A novel interface-treated micromechanics approach for accurate and
           efficient modeling of CNT/polymer composites
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Majid Karimi, Rahmatollah Ghajar, Abbas Montazeri In this paper, a two-step incremental micromechanics formulation in conjunction with FEM and weakened interface model is utilized to characterize elasto-plastic behavior of CNT/polymer nanocomposites. For the validation purpose, results corresponding to the perfect bonding assumption are compared with the experimental data. The micromechanics approach considering the weakened interface is extended to represent the nanotube, its surrounding polymer and the interfacial interactions via an equivalent fiber. The most important factor in the developed method is the sliding parameter determined through comparing the results of the model with that of a molecular structural mechanics-finite element multiscale approach at various loading conditions. Subsequently, employing several case studies, various aspects of the effects of interfacial strength on the elastoplastic behavior of these nanocomposites are systematically examined. The results show that the interfacial bonding characteristics plays a crucial role in enhancing the mechanical behavior of the host polymer and thus, should be thoroughly studied.
       
  • An extended Ritz formulation for buckling and post-buckling analysis of
           cracked multilayered plates
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): A. Milazzo, I. Benedetti, V. Gulizzi An extended Ritz formulation for the analysis of buckling and post-buckling behaviour of cracked composite multilayered plates is presented. The formulation is based on: (i) the First-order Shear Deformation Theory to model the mechanics of the multilayered plate; (ii) the von Kármán’s theory to account for geometric non-linearities; (iii) the use of an extended set of approximating functions able to model the presence of an embedded or edge crack and to capture the crack opening fields as well as the global behaviour within a single cracked domain. The numerical results of the buckling analyses and the equilibrium paths in the post-buckling regime are compared with the results from finite elements simulations, confirming the accuracy and potential of the formulation.
       
  • A planar finite element formulation for corrugated laminates under
           transverse shear loading
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): D.T. Filipovic, G.R. Kress This paper contributes a planar finite-element unit-cell formulation based on the principle of virtual displacements for simulating the structural as well as the local transverse-shear response of thick-walled corrugated laminates. The theory observes that bending-strain gradients are invariable under constant internal force held in equilibrium by the transverse shear stresses in the corrugated cross-section. It is explained how the load information is transmitted by macro strains which are valid for arbitrary laminates. The unit-cell model assumes periodicity of the corrugation pattern and homogeneity of the global load. Postprocessing aspects include best-fit of the warped cross-section to a vertical plane and extrapolation of the secondary solutions with quadratic polynomials fitted to results at the Barlow points of a Lagrange type finite element with cubic shape functions. Simulation results with the proprietary software show peculiar stress redistributions and it is explained how these are caused by an interplay of geometry, equilibrium, and homogeneous natural boundary conditions. A convergence study along with model verification is included.
       
  • Numerical and experimental study on hydroelasticity in water-entry problem
           of a composite ship-hull structure
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Hang Xie, Huilong Ren, Sen Qu, Haoyun Tang The problem of hydroelastic impact draws immense attention in marine structural design due to the complex interactions between structure and fluid. In this study, the water entry problem of a composite ship-hull structure, which is one segment of an idealized ship bottom structure, is investigated. This structure was made of composite lightweight structures and the bottom panel consists of 3 longitudinal stiffeners and 2 transverse frames. In the numerical model, a CFD solver and a FEM solver are coupled through the interface of structure and fluid, and solved through using a partitioned approach. Correspondingly, a series of drop tests of this structure were conducted. The falling displacement, acceleration, pressure and stress responses were measured and the experimental uncertainty was studied through analyzing the repeatability, symmetry and oscillations. Numerical results were compared with the experimental ones, and reasonable agreements on falling kinemics, slamming loads and stress responses are achieved. Meanwhile, the hydroelastic effects on the hydrodynamic pressure and stress responses were discussed through analyzing the natural frequency of structure. High hydroelastic effects are observed and more than one mode shape dominates the structural deformation in case of hydroelastic impact.
       
  • Periodic boundary conditions for FE analyses of a representative volume
           element for composite laminates with one cracked ply and delaminations
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): L. Maragoni, P.A. Carraro, M. Quaresimin In this work, a periodic laminate Representative Volume Element (RVE) is developed for composite laminates having cracks in a single ply and delaminations originated from those cracks. The boundary conditions to be applied for a Finite Element (FE) analysis are illustrated in details for different loading conditions, namely longitudinal, transverse, and shear stress, as well as for temperature gradient. The proposed RVE can be used to calculate the elastic properties of a damaged laminate, the stress trends in each ply, the Energy Release Rate (ERR) of the off-axis cracks and the ERR of the delaminations. Some examples are reported for each of those applications. Eventually, the proposed laminate RVE is validated against FE of full laminates and experimental data.
       
  • Micro-mechanical FE numerical model for masonry curved pillars reinforced
           with FRP strips subjected to single lap shear tests
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Elisa Bertolesi, Gabriele Milani, Mario Fagone, Tommaso Rotunno, Ernesto Grande The present paper discusses the results obtained by using a micro-mechanical FE numerical model for the study the bond behavior of some curved specimens strengthened by Fiber Reinforced Polymer (FRP) composite materials. The numerical model, implemented into the FE code Abaqus, is a sophisticated micro-modelling (heterogeneous) approach, where bricks and mortar are meshed separately by means of 4-noded plane strain elements exhibiting distinct damage in tension and compression, FRP is assumed elastic and an elastic uncoupled cohesive layer is interposed between FRP reinforcement and masonry pillar. The experimental investigation considered to benchmark the numerical approach is aimed at characterizing the influence of normal stresses induced by curved supports on the stress-transfer mechanism of FRP materials. To this scope some single lap shear tests performed at the University of Florence on FRP reinforced curved pillars with two different curvature radii (1500 and 3000 mm) are here considered. The obtained numerical results show a promising match with experimental evidences, in terms of elastic stiffness, peak loads and post-peak behavior. Indeed, the proposed approach allows to correctly account for important local effects, such as the effect of FRP-masonry interfacial normal stresses on the global delamination strength and the distribution of damage in the pillar volume. By using the proposed modelling approach, comprehensive numerical sensitivity analyses to investigate the role played by the curvature on the ultimate delamination strength, are also presented in the paper.
       
  • Cyclic stress-strain model for FRP-confined concrete considering post-peak
           softening
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Pengda Li, Yu-Fei Wu, Yingwu Zhou, Feng Xing The majority of existing cyclic stress–strain models for fiber reinforced polymer (FRP) confined concrete are applicable only to cases where post-peak strain hardening occurs. Cyclic model catering for strain softening is rare due to the lack of sufficient experimental data. Recent experimental tests on FRP-confined concrete cylinders involving strain-softening have identified new factors that have a significant effect on the cyclic behavior. Through an analytical study, a newly defined parameter, the effective confinement rigidity, is found to be a key factor governing the cyclic softening and hardening. By including the additional key factors and using the latest database with more strain-softening cyclic stress–strain curves, a stress–strain model of FRP-confined concrete subjected to cyclic loading considering both post-peak hardening and softening is proposed. Compared with the existing models, the proposed model can predict the cyclic behavior of FRP-confined concrete with better accuracy.
       
  • Static and dynamic bending behaviors of carbon fiber reinforced composite
           cantilever cylinders
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Hui Xu, Lei Zu, Bing Zhang, Houfeng You, Debao Li, Huabi Wang, Bin Zi In this paper a carbon fiber reinforced composite cantilever cylinder under gravity was designed using the cantilever beam theory. The finite element model of the composite cantilever cylinder was established using software ANSYS. The static and dynamic bending responses of the cantilever cylinder were investigated with the aid of the finite element method and theory of flexible multi-body dynamics. The deflection calculated using fully constraints at the root of the cantilever cylinder under gravity satisfies the design requirements. Moreover, the response curves of deflections of the cantilever cylinder with time were obtained in terms of the step motion and sinusoidal motion, respectively, using software ADAMS. The deflections of the cantilever cylinder were also evaluated for various motions. The results indicate that the maximum deflections of the cantilever cylinder for the both motion modes do not exceed the allowable design values. The present models and methods are able to provide a useful reference for design and production of carbon fiber composite cantilever cylinders.
       
  • Nonlinear transient isogeometric analysis of FG-CNTRC nanoplates in
           thermal environments
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): P. Phung-Van, Cuong-Le Thanh, H. Nguyen-Xuan, M. Abdel-Wahab This paper presents size-dependency effects on nonlinear transient dynamic response of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) nanoplates under a transverse uniform load in thermal environments. To consider the length scale and size-dependency effect of nanostructures, a nonlocal continuum theory of Eringen is adopted. The nonlocal governing equations for nanoplate theory are derived from the Hamilton’s principle and approximated by using isogeometric analysis associated with the higher-order shear deformation theory. A numerical model based on the von Kármán strains and Newmark time integration scheme is employed to solve geometrically nonlinear transient problems. The material properties of the FG-CNTRC nanoplate are assumed to be graded and temperature-dependent in the thickness direction, which are expressed through a micromechanical model. Effects of nonlocal parameter, carbon nanotube volume fraction, length-to-thickness ratio, distributions of carbon nanotubes and temperatures through thickness are investigated in detail. Several numerical results show the reliability of the present method.
       
  • Three-dimensional hygrothermal vibration of multilayered cylindrical
           shells
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Tiangui Ye, Guoyong Jin, Siyang Gao The rise in moisture concentration and temperature reduces both strength and stiffness of composites. A thorough understanding of the effects of temperature and moisture concentration in composite structures is critical in ensuring safety design. There seems to be no such solutions available for multilayered composite cylindrical shells. This paper is therefore devoted to the three-dimensional hygrothermal vibration analysis of multilayered cylindrical shells under general boundary conditions for the first time. The formulation is based on the 3-D elasticity theory. The vibrational displacement field is numerically discretized by the sampling surface technique in the transfer domain and approximated by the spectral method in the remaining domains. The transverse deformations and interlaminate continuities are taken into account in combination with differential-quadrature concept. The governing equations are finally derived in a modified variational form for constrained system and the boundary conditions are taken into account in a unified form by utilizing penalty functions and Lagrange multipliers. The boundary conditions may be free, simply-supported, clamped or/and elastically restrained. The solutions match well with those reported in the literature in verification. The effects of hygrothermal environment, boundary conditions, shell geometry, lamination are brought out and discussed through parametric study.
       
  • A new numerical method for the mechanical analysis of chopped carbon fiber
           tape-reinforced thermoplastics
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Peng Qu, Yi Wan, Chunjiang Bao, Qun Sun, Guangqiang Fang, Jun Takahashi Discontinuous carbon fiber-reinforced thermoplastics (DCFRTP) are promising materials for the fabrication of complex parts. In predicting the mechanical properties of DCFRTP with randomly oriented reinforcement, the application of numerical methods, which employ homogeneous models, is limited because the mesoscopic structural parameters influencing mechanical properties are not adequately represented in the macroscopic numerical model. On the basis of the peridynamic (PD) theory, a new numerical method, which employs a heterogeneous particle model, is proposed in this investigation for the mechanical analysis of DCFRTP. The tensile properties of ultra-thin chopped carbon fiber tape-reinforced thermoplastics (UT-CTT) are investigated using this numerical method. The relationship between PD horizon size and characteristic size of UT-CTT is discussed. The effect of model size on the scattering of the tensile properties is analyzed and the influence of interface properties on crack propagation is investigated. A comparison between PD simulations and experimental results indicated a good agreement.
       
  • Compressive and shear properties of carbon fiber composite square
           honeycombs with optimized high-modulus hierarchical phases
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Li-Jia Feng, Zhi-Tao Yang, Guo-Cai Yu, Xiao-Jian Chen, Lin-Zhi Wu This paper focuses on strengthening carbon fiber hierarchical composite square honeycomb structures (HCSH) by selecting high-modulus hierarchical phase and optimizing its thickness. HCSH have been manufactured from carbon fiber composite foam sandwich structures by a simple snap-fit and bonding method. The measured compressive and shear strengths are shown to be well predicted by micromechanics failure models of HCSH. Compared to the monolithic composite square honeycomb structures (CSH), the measured specific out-of-plane compressive strength of HCSH improves to approximately 330% and the specific shear strength improves to about 180%. Furthermore, the relationships between hierarchical phase modulus and its optimum thickness are developed to design the optimum HCSH. Carbon fiber HCSH are found to exhibit better mechanical properties than other cellular structures, and thus provide new opportunities for light-weight multifunctional sandwich structures.
       
  • Analysis of ballistic resistance of composites based on EN AC-44200
           aluminum alloy reinforced with Al2O3 particles
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Adam Kurzawa, Dariusz Pyka, Krzysztof Jamroziak, Miroslaw Bocian, Piotr Kotowski, Pawel Widomski The work presents the research conducted on the impact resistance of newly developed metal-ceramic composites with aluminum matrix on firing with 5.56 × 45 mm caliber intermediate ammunition. For this purpose, materials based on AC-44200 alloy reinforced with Al2O3 particles were made using the squeeze casting method. The ballistic resistance was compared between the shot composites with 20% vol. and 40% vol. of Al2O3 particles and the shot material of the non-reinforced matrix. The ABAQUS program was used to carry out the preliminary analysis of ballistic resistance of the composites. The performed works also included homogenization through the Representative Volume Element (RVE), the 3D geometry of the 5.56 mm SS109 projectile and the simulations in the scope of shooting through materials. In the basic research, the shot samples of composite materials were subjected to the thorough metallographic analysis with the explanation of the mechanism of scrap formation while being shot. As a result of the tests and analyzes, conclusions were drawn on the application possibilities of aluminum composites reinforced with Al2O3 particles in construction of add-on-armor protection structures.
       
  • Timber-mortar composites: The effect of sol-gel surface modification on
           the wood-adhesive interface
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Sanja Kostic, Vivian Merk, John K. Berg, Philipp Hass, Ingo Burgert, Etienne Cabane Timber-mortar composite structures require rigid, strong, but also ductile connections to optimize their performances. Up to now, the preferred connection systems were based on metal fasteners and notches in wood. In this study, an alternative approach based on a fully glued connection was studied (using an epoxy-based system), and a wood pre-treatment was applied in order to enhance the compatibility and the adhesion properties at the interface between beech wood and mortar. The wood surface was functionalized with a xerogel obtained by means of a sol-gel process, consisting of two layers of silane nanofilms – namely tetra-ethoxysilane and (3-Aminopropyl) triethoxysilane. Chemical analysis of the wood surface confirmed the chemical bonding of the silanes. Microscopy images revealed that the silane pre-treatment also affects adhesive penetration into the wood. In terms of mechanical properties, 3-point bending tests on pre-treated beech wood-mortar samples showed an improved load bearing capacity in comparison to unmodified wood-mortar specimens.
       
  • Experimental and simulation investigation of temperature effects on modal
           characteristics of composite honeycomb structure
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Yunhe Bai, Kaiping Yu, Jie Zhao, Rui Zhao Modal analysis is the basis of the structural dynamics design and optimization. When operating in a thermal environment, the structure may be affected by the temperature in diverse aspects. In this paper, a sandwich structure composed of carbon fiber woven skins and a Nomex honeycomb core is taken as the research object. Temperature effects on its modal characteristics are investigated by experiments and simulations. During the test, natural frequencies and modal damping ratios of the specimen change with temperature dramatically, while each mode exhibits a particular trend. Although the temperature-dependent material property of the skin is identified as the essential factor of the variations in the modal parameters, the modulus components of the skin material have different sensitivities to the temperature change. As a result, correlations between the natural frequencies and modulus components are related to the corresponding mode shapes. And these correlations are studied by the finite element analysis.
       
  • A review of analytical models to describe pull-out behavior –
           Fiber/matrix adhesion
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Fatiha Teklal, Arezki Djebbar, Samir Allaoui, Gilles Hivet, Yoann Joliff, Bachir Kacimi Micromechanical tests are reliable tools to study the failure mechanisms in composites reinforced with continuous fibers. This paper presents an overview of various analytical models developed to study the pullout (push-back) behavior of a fiber embedded in a matrix block to characterize the fiber/matrix interfacial adhesion. Two approaches can be distinguished: one based on a maximum stress criterion (shear lag) and the other based on fracture mechanics. This article gives an overview of the analytical models reported in the literature to measure the shear strength and critical fracture energy at the interface, the parameters influencing these properties, the geometry of the model, embedded length of the fiber, fiber diameter and loading conditions (opening width between the knife-edges for example), including components (fiber, matrix, interface), manufacturing route and the resulting defects.
       
  • An experimental and numerical study into the development of FRP guyed
           towers
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Sami A. Alshurafa, Dimos Polyzois A research project has been carried out at the University of Manitoba, Canada, to develop fibre-reinforced polymer (FRP) meteorological guyed towers. Both theoretical and experimental results are presented in this paper. The theoretical work involved the development of finite element models to analyze the structural behavior of an 81 m tower. The experimental work involved the testing of an 8.6 m long segment, representing the bottom segment of the 81 m guyed tower used in the analysis, under static and dynamic loading. This segment was constructed from three cells bonded together with epoxy resin to form an equilateral triangle shape. Each cell was fabricated using four layers of glass fibre matting for a total thickness of 5 mm with a sequence of [90°/0°/0°/90°] impregnated in epoxy resin. An extensive material testing program was also carried out to define the material properties for finite element analysis. The numerical results are compared with the experimental results to confirm the validity of the finite element models.
       
  • Inherently multifunctional geopolymeric cementitious composite as
           electrical energy storage and self-sensing structural material
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): M. Saafi, A. Gullane, B. Huang, H. Sadeghi, J. Ye, F. Sadeghi In this paper, we demonstrate for the first time that potassium-geopolymeric (KGP) cementitious composites can be tuned to store and deliver energy, and sense themselves without adding any functional additives or physical sensors, thus creating intelligent concrete structures with built-in capacitors for electrical storage and sensors for structural health monitoring. Density function theory (DFT)-based simulations were performed to determine the electronic properties of the KGP cementitious composite and understand its conduction mechanism. Experimental characterization was also conducted to determine the structure, chemical composition, conduction mechanism, energy storage and sensing capabilities of the KGP cementitious composite. The DFT simulations suggested that the KGP cementitious composite relies on the diffusion of potassium (K+) ions to store electrical energy and sense mechanical stresses. The geopolymeric cementitious composite exhibited a good room temperature ionic conductivity in the range of 12 (10−2 S/m) and an activation energy as high as 0.97 eV. The maximum power density of the KGP capacitors is about 0.33  kW/m2 with a discharge life of about 2 h. The KGP stress sensors showed high sensitivity to compressive stress: 11 Ω/MPa based on impedance measurement and 0.55 deg/MPa based on phase measurement. With further development and characterization, the KGP cementitious composite can be an integral part of concrete structures in the form of a battery to store and deliver power, and sensors to monitor the structural integrity of urban infrastructure such as bridges, buildings and roads.
       
  • Analysis of defect detectability in polymeric composites using
           self-heating based vibrothermography
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Andrzej Katunin, Dominik Wachla The self-heating based vibrothermography (SHVT) is a new non-destructive testing method dedicated for testing of polymer matrix composite structures, where the excitation is performed by externally applied mechanical vibrations in a low frequency range. Exciting a structure with several resonant frequencies, the heating up of this structure is possible due to the occurrence of the thermoviscoleastic effect called the self-heating, whose nature originates from the mechanical energy dissipation. In order to examine an efficiency of the SHVT an analysis of defect detectability on composite specimens with milled artificial defects was performed. The post-processing of the series of resulting thermograms was performed in order to enhance defect detectability. The obtained results allow to conclude about high efficiency of SHVT NDT technique, which can be used especially in cases when a direct access to the testing structure in order to excite it externally is difficult or impossible.
       
  • Dynamic characteristics of composite tilting pad journal bearing for
           turbine/generator applications
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Seung Yoon On, Yun Seong Kim, Jun Il You, Jun Woo Lim, Seong Su Kim Tilting pad journal bearings have been employed for turbine, compressor, pump, and generator applications owing to their high loading capacity, excellent stability, and service durability at high operation speed compared to conventional journal bearings. For high-speed and high-performance applications, tilting pad journal bearings should reduce the rotor vibration. Therefore, the bearings are designed to have excellent damping characteristics. In this study, composite tilting pad journal bearings consisting of carbon fiber/epoxy composites and a backup metal are fabricated to increase the dynamic performance and durability. A modal analysis is performed to investigate dynamic stability of the composite tilting pad. Moreover, the damping coefficient of fluid film, oil film pressure, and orbit of rotor are calculated with respect to the liner materials under a hydrodynamic lubrication state. To verify the analysis results, hydrodynamic lubrication tests of composite and white metal tilting pad journal bearings are conducted using an industrial test bench. As a result, the composite tilting pad journal bearing has effectively reduced the rotor vibration and increased the stability and durability of the bearing system compared to the white metal tilting pad journal bearing.
       
  • Wave component solutions of free vibration and mode damping loss factor of
           finite length periodic beam structure with damping material
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Yongbin Ma, Kai Zhang, Zichen Deng Free vibration and mode damping loss factor of the finite periodic beam structure with viscoelastic damping material are investigated in this paper based on wave component method. A simple iterative operation for the natural vibration modes of the beam structure is firstly proposed by considering that the mode shape can be formed through superposition of the wave shapes of the wave components of the beam structure at the corresponding natural frequency. And then, wave component solution of the mode damping loss factor of the beam structure is obtained and analyzed based on the modal stain energy method. It is found that the kinetic energy of the unit cell of propagative wave component is always the same with the strain energy, and for non-propagative wave component these two quantities will never be equal. In numerical examples, the proposed iterative operation is validated.
       
  • Effect of using CFRP wraps on the strength and ductility behaviors of
           exterior reinforced concrete joint
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Yazan B. Abu Tahnat, Mahmud M.S. Dwaikat, Mohammad A. Samaaneh One considerable weakness in reinforced concrete (R.C) structures is the connection between beams and columns. Several researchers showed that R.C joints suffer brittle failure due to combined effect of loading on the joints. Therefore, the ductility of the beam-column joints in R.C structures is an essential factor to prevent sudden failure of the joint. Different techniques were adapted by several researchers to increase the ductility and strength of beam-column joints including the use of high strength concrete, special stirrups and reinforcement configuration, steel plates and Fiber-Reinforced Polymer (FRP).One way to improve the ductility of such joints is the use of FRP sheet wraps. This research focuses on studying the effect of using FRP wraps around beam on ductility of exterior R.C beam-column joints. To achieve this main objective; this research focuses on the key parameters controlling ductility of joints, namely, relative inertia of column to beam (G), amount of transverse steel in joint (Av/s)J and amount of transverse steel in beam (Av/s)B. Finite Element (F.E.) analysis using commercial F.E. software (ABAQUS) is used to investigate the ductility behavior of R.C joints strengthened by FRP. The mentioned parameters are investigated numerically. Results show that the using CFRP wraps around beam converts the brittle failure to ductile failure. Stirrups continuity inside the joint increases the capacity and ductility for models dominated by shear failure.
       
  • Experimental and numerical investigation of mechanical behaviors of 2.5D
           woven composites at ambient and un-ambient temperatures
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Jian Song, Weidong Wen, Haitao Cui An angle-interlock 2.5D woven composites (2.5D-WC), as a man-made new structural layout in the family of woven composites, have recently attracted increasing interest in its promising applications in the fields of astronautics and aeronautics. Nevertheless, published results are rarely associated with the temperature-dependent mechanical behaviors of this material. The current work emphasizes on the evaluation of the thermo-mechanical behaviors, damage propagation and failure mechanisms of 2.5D-WC at ambient and un-ambient temperatures by using experimental and numerical approaches. Experimental results show warp mechanical modulus and strength experience a decrease trend when the temperature increases. However, the weft strength is not sensitive to temperature, giving an indication of anisotropic behavior. There is no necking phenomenon near the fracture surface regardless of temperature and loading direction, indicating a brittle fracture mode. Temperature and fiber yarn arrangement direction play a critical role in alternating the damage propagation and failure mechanisms. Additionally, simulation results quantitatively elaborate the corresponding experimental findings and proposed mechanisms, which can be used to evaluate the temperature-dependent mechanical behaviors of 2.5D-WC. Ultimately, we hope these findings could further promote the engineering applications of 2.5D-WC, especially in aero-engine fields.
       
  • Experimental study on delamination migration in multidirectional laminates
           under mode II static and fatigue loading, with comparison to mode I
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Yu Gong, Bing Zhang, Supratik Mukhopadhyay, Stephen R. Hallett This paper presents an experimental investigation to better understand the mechanisms of delamination migration in multidirectional End Loaded Split (ELS) specimens. A stacking sequence susceptible to delamination migration was selected for this study and subjected to pure mode II static and fatigue loading. The static and fatigue results gave comparable migration mechanisms, however, differences were noted regarding the damage sequence, the fracture surface, the migration angle and the horizontal distances of migrated location to the front of pre-crack. Scanning Electron Microscopy (SEM) results indicated that fibre imprints and cusps were two dominant micro-features on the fracture surfaces for all specimens. Interactions between delamination and ply splits were observed and confirmed by X-ray CT scanning. Furthermore, comparison was made to understand the effects of loading modes (mode I and II) on delamination migration.
       
  • Three-point bending of sandwich beam with special structure of the core
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Piotr Paczos, Radoslaw Wichniarek, Krzysztof Magnucki The subject of the study are short sandwich beams with special structure of the core (honeycomb). The beam is made using additive manufacturing technology. The values of elastic modules vary along beam. The linear shear deformation theory – the “zig-zag” hypothesis is assumed for plane cross section. The analytical model of beam is based on this hypothesis. The deflection of beam is analytically calculated. Moreover, the deflection of beam is experimentally determined on a test stand. The results of these two methods are compared.
       
  • A strain-rate-dependent damage model for evaluating the low velocity
           impact induced damage of composite laminates
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Kangkang Wang, Libin Zhao, Haiming Hong, Jianyu Zhang Low velocity impact (LVI) has always been a potential threaten to composite structures. This out-of-plane dynamic impact load easily leads to a dramatic increase of the strain state in the material transverse plane, which can affect the dynamic stress state and damage evolution of the composite laminate, especially for LVI with a relatively high energy. However, the strain rate effect was always neglected in existing investigations, thus introducing inevitable errors in numerical predictions for engineering practices. To accurately capture the failure process of composite laminates under LVI, a three-dimensional strain-rate-dependent damage model was proposed. This model was composed of three parts: a modified stress–strain relationship for composites under a dynamic stress state; a strain-rate-dependent progressive damage model to evaluate the intra-laminar damage; and a cohesive zone model to examine the inter-laminar delamination. LVI tests with different impact energies were conducted to provide validating data. It is shown that the numerical results from the strain-rate-dependent damage model are highly consistent with the experimental outcomes. The contact force history curves, intra- and inter-laminar damage evolution process are found to be strain rate dependent, and thus the numerical errors predicted by the strain-rate-independent damage model significantly increase with the increment of the applied impact energy, which is unacceptable in practice for LVI with relatively high impact energies.
       
  • A simple first-order shear deformation theory for vibro-acoustic analysis
           of the laminated rectangular fluid-structure coupling system
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Hong Zhang, Dongyan Shi, Shuai Zha, Qingshan Wang This paper presents a simple first-order shear deformation theory (SFSDT), which is used for the first time to analyze the vibro-acoustic characteristics of the laminated rectangular plate-cavity coupling system filled with air or water. The proposed theory contains only four unknowns and has greater application scope and higher computation accuracy compared with the classical plate theory (CPT). The admissible functions of displacements and sound pressure of the fluid-structure coupling system are expressed as superposition of the periodic functions based on the Fourier series method. Combined with the artificial virtual spring technology, the proposed theory could be used to analyze the composite coupling system under various combinations of classical boundary conditions or arbitrary elastic boundary conditions. Based on the free vibration analysis of the laminated rectangular plate in-vacuo, both the natural characteristics analysis and the forced response analysis under the excitation of a unit point force or a unit point sound source are carried out. The differences between the weak coupling system with air as medium and the strong coupling system with water as medium are discussed in detail and some new results and new conclusions have been given, which could be the benchmark for the future research.
       
  • Generation of the representative volume elements of composite materials
           with misaligned inclusions
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Witold Ogierman, Grzegorz Kokot The paper presents the novel method of generation of the representative volume elements of composite materials with misaligned inclusions. The novel method, that is based on the solution of the optimization problem, allows to represent the prescribed orientation distribution by applying a reduced number of inclusions, in compariswwwwwon with other methods presented in the literature. The accuracy of the proposed method is demonstrated by the analysis of exemplary orientation distributions. Both the orientation state reconstruction accuracy and the effective material properties prediction accuracy are investigated. Moreover, the effective material properties determined on the basis of the representative volume elements with a reduced number of inclusions are compared with the results of the analysis of representative volume elements containing a large number of inclusions.
       
  • Static nonlinear model of both ends clamped magnetoelectric
           heterostructures with fully magneto-mechanical coupling
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Yikun Yang, Muqing Niu, Bintang Yang A static fully magneto-mechanical coupling nonlinear model of magnetoelectric (ME) effect in both ends clamped magnetostrictive/piezoelectric heterostructures is established. The magnetoelectric effect, which arose from piezoelectric effect driven by magnetostrictive force, is studied. As the both ends of the heterostructures are fixed, the piezoelectric material can be equivalent to the linear spring load of magnetostrictive actuator. The nonlinear theoretical model is built based on a nonlinear magnetostrictive constitutive relation and a linear piezoelectric model. The hysteresis and fully coupled magneto-mechanical effects, including stress-dependent magnetization, stress-dependent magnetostriction and ΔE effect of magnetostrictive material are considered in this model. Using the model, the influence of the pre-stress, magnetic field and the length fraction of the magnetostrictive material on the magnetoelectric response is qualitatively predicted. Furthermore, the model can explain the “self-biased” response caused by the hysteretic characteristics of the ME composites. A ME heterostructures prototype is designed and manufactured based on Terfenol-D/PZT heterostructures. The model is validated by comparing the simulated ME response with experiment at the quasi-static condition. The nonlinear ME model provides a theoretical basis for the optimization design of high-performance ME devices.
       
  • Optimal design of triaxial weave fabric composites under tension
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Zhenzhou Wang, Jiangbo Bai, Adam Sobey, Junjiang Xiong, Ajit Shenoi Triaxial weave fabrics are increasingly used in ultralight structures, such as the wings of unmanned aerial vehicles (UAVs) and deployable antenna on spacecraft. The tensile strength to stiffness ratio for these applications is important, requiring an optimal weave pattern; in this paper Genetic Algorithms are used to improve these designs. The mechanical response is obtained using the minimum total complementary potential energy principle where the yarns are approximated as curved beams in a micromechanical unit cell. Leading Genetic Algorithms are benchmarked to determine which perform best. The results form a disconnected Pareto front where the left hand part can be used for flexible structures but is difficult to find. An overall improvement in strength to stiffness ratio of 1191% is made with 643 designs found better than a current example. The selection of the Genetic Algorithm is shown to be crucial with only MLSGA-NSGAII regularly finding the entire Pareto front.
       
  • Design and manufacture of a dual-functional exterior wall structure for
           1.1–5 GHz electromagnetic radiation absorption
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Shuai Xie, Zhijiang Ji, Zhonghe Shui, Bin Li, Jing Wang, Guoyan Hou, Jimei Wang In order to solve the increasing serious electromagnetic (EM) radiation pollution, this paper presents a dual-functional exterior wall structure for EM radiation protection. The EM wave absorption properties of the exterior wall structure were investigated in 1.1–5 GHz using arch reflecting method, and results indicate that the optimal absorption property with effective bandwidth below −10 dB reaches 3.7 GHz (1.1–4.8 GHz) can be obtained by the combination of periodic structure and multi-layer structure. The destructive interference, dielectric loss of carbon black (CB), and multiple reflection and scattering of expanded perlites (EP) are the main EM wave absorption mechanisms. The absorption peaks of reflection loss curves are caused by destructive interference, and effective bandwidth is determined by the dielectric loss capacity of CB. Moreover, the multiple reflection and scattering of EP particles play a major role in EM wave absorption. It is expected that the devised exterior wall structure has great potentials in EM radiation protection.
       
  • On a robust FE2 model for delamination analysis in composite
           structures
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): T. Herwig, W. Wagner The present paper deals with a robust two-scale delamination model based on a FE2 formulation, whereby a finite element model on the macro- and meso-scale are solved simultaneously. For a correct modeling of the delamination kinematics, the composite structure on macro-scale is discretized by a combined element. Only one single integration point over the full height of the composite structure contains the information about shell and interfacial kinematics, allowing a straight forward enhancement to the FE2 model. On the meso-scale, the combined kinematics are applied to a coupled representative volume element (cRVE), which describes the entire stacking sequence including an interfacial layer. The coupling between the shell and the interfacial kinematics results in a more robust delamination model. Numerical examples demonstrate the applicability and the improvements by reducing the oscillations of the load displacement curve during the softening process and the influence of the macroscopic mesh discretization under single and mixed mode loading.
       
  • Advanced nonlinear dynamic modelling of bi-stable composite plates
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Zhangming Wu, Hao Li, Michael I. Friswell This paper proposes a novel analytical model to study the nonlinear dynamics of cross-ply bi-stable composite plates. Based on Hamilton’s principle, in conjunction with the Rayleigh-Ritz method, an advanced analytical model with only 17 unknown terms is developed to predict the entire nonlinear dynamic response of bi-stable composite plates, which are excited by an electrodynamic shaker. The coupling between the bi-stable plate and the shaker is considered in the development of the analytical model. This work, for the first time, simulates the full dynamics of bi-stable plates using an analytical model, including the prediction of the nonlinear characteristics of single well vibration and cross well vibration. Numerical results on three vibrational patterns of two standard cross-ply composite plates are obtained to study the nonlinear dynamics of bi-stable plates. The prediction accuracy on the dynamic characteristics of different vibrational patterns of bi-stable plates are verified by both finite element analysis (FEA) and experimental results. Large amplitude cross-well vibrations due to the transitions between different stable states of bi-stable plates are also characterized accurately. Applying this 17-term analytical model for the dynamic analysis of bi-stable plates is straightforward, as the mass and stiffness properties are obtained directly from the geometry and material properties. Only the damping coefficients for different plates need to be determined from experiments. Furthermore, this proposed 17-term analytical model has much higher computational efficiency than FEA.
       
  • Optimisation of local in-plane constraining forces in double diaphragm
           forming
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): S. Chen, O.P.L. McGregor, L.T. Harper, A. Endruweit, N.A. Warrior Rigid blocks (risers) were introduced in the double diaphragm forming (DDF) process to change the local in-plane strain distribution in the diaphragms, aimed at reducing wrinkling defects in the production of fabric preforms. A two-step optimisation method was developed to determine the position and dimension of each riser. In Step I, optimisation of the riser position was conducted using a simplified finite element (FE) model coupled with a genetic algorithm (GA). The height of each riser was optimised in Step II using a detailed FE model with the optimised riser positions from Step I. For demonstration, a hemisphere preform was manufactured by DDF using the optimum riser arrangement established by the optimisation routine. Results indicate that the optimum riser pattern (shape and position relative to the component boundary) can dramatically improve the preform quality through reduction of out-of-plane wrinkles, validating the feasibility of the two-step routine.
       
  • An experimental study on the effect of adding multi-walled carbon
           nanotubes on high-velocity impact behavior of fiber metal laminates
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): H. Khoramishad, H. Alikhani, S. Dariushi In this paper, the effect of adding multi-walled carbon nanotubes (MWCNTs) on high-velocity impact behavior of fiber metal laminates (FMLs) was investigated. The unreinforced and reinforced FMLs with different MWCNT weight percentages of 0.25, 0.5 and 1 were manufactured and tested under high-velocity impact loading using a gas gun and a spherical projectile. Moreover, tensile tests were performed on the unreinforced and reinforced composite laminates of FMLs. Incorporating 0.5 wt% of MWCNTs into the composite laminate of FML resulted the maximum reduction of 29.8% in projectile residual velocity and the maximum increase of 18.9% in the absorbed energy during projectile perforation compared to the unreinforced FMLs. This was consistent with the tensile test results in which maximum improvements in the strength, stiffness and toughness were obtained for the 0.5 wt% MWCNT-nanocomposite. The detailed visual inspections and SEM images showed that adding MWCNTs improved the resin-fiber adhesion consequently reduced the composite delamination and matrix cracking. Conversely, MWCNTs weakened bonding between the aluminum and composite layers and allowed the aluminum layer to experience larger plastic deformation.
       
  • A water-soluble magnesium sulfate bonded sand core material for
           manufacturing hollow composite castings
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Fuchu Liu, Peng Jiang, Ying Huang, Wenming Jiang, Xinwang Liu, Zitian Fan A high-strength and water-soluble magnesium sulfate bonded sand core (WSMBS) material cured by twice microwave heating was successfully fabricated using magnesium sulfate aqueous solution as a binder, which is suitable for manufacturing hollow composite structures castings. The effects of various factors on the properties of WSMBS were investigated. The results shows that WSMBS possesses some advantages of good water solubility, high curing speed and strength. The tensile strength of WSMBS is more than 0.6 MPa under optimal parameters, and when the temperature of WSMBS ranges from 105 °C to 116 °C, the tensile strength is superior and MgSO4·7H2O is dehydrated to MgSO4·4H2O or MgSO4·3H2O. The moisture absorbability of WSMBS is quite high, and it rises with increasing the stored time and the magnesium sulfate binder content. The scanning electron microscope analysis shows that there are some micro-cracks or holes in the bonding bridge that decreases the strength of WSMBS after being put in humidistat for several hours. The energy dispersive X-ray analysis shows that the bonding bridge mainly comprises magnesium sulfate and so the use of WSMBS in casting does not release toxic gases. The water-solubility rate of WSMBS is 57.9 kg·min−1·m−2, which can be dissolved in water quickly after casting and overcome the poor leachability of the common bonded sand core, and therefore the used WSMBS can be easily reclaimed by water scrubbing method and the use of WSMBS can improve the production efficiency of the complex hollow composite castings with many interior channels or passages, undercuts. What is more, the aqueous solution of magnesium sulfate can be made from waste water which is used for dissolving the sand core after casting, and therefore it can realize green casting with no toxic gas during casting and recycling magnesium sulfate binder.
       
  • Interfacial behavior and debonding failures of full-scale
           CFRP-strengthened H-section steel beams
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Jun-Jie Zeng, Wan-Yang Gao, Feng Liu Strengthening existing steel beams with externally bonded carbon fiber-reinforced polymer (CFRP) plate has attracted many interests in the research community. Debonding of the CFRP plate is the dominant failure mode in a flexurally strengthened steel beam, and the debonding failure is controlled by the interfacial responses between the CFRP plate and the substrate steel beam. Although some experimental investigations have been conducted on CFRP-strengthened steel beams, limited test results on the interfacial stress and strain responses especially in full-scale steel beams, are available to verify the numerical modeling. This paper presents an experimental study on the flexural behavior of full-scale CFRP-strengthened H-section steel beams. The effects of different bond lengths of CFRP plates and the presence of steel stiffeners are investigated. The test results in terms of the failure modes, load-deflection responses, CFRP strains, interfacial shear stress distributions are reported in detail. A three-dimensional finite element model is proposed to predict the flexural performance of full-scale CFRP-strengthened steel beams, and it is then validated extensively by the test results.
       
  • A general multi-scale two-level optimisation strategy for designing
           composite stiffened panels
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Marco Montemurro, Alfonso Pagani, Giacinto Alberto Fiordilino, Jérôme Pailhès, Erasmo Carrera This work deals with the problem of the least-weight design of a composite stiffened panel subject to constraints of different nature (mechanical, geometrical and manufacturability requirements). To face this problem, a multi-scale two-level (MS2L) design methodology is proposed. This approach aims at optimising simultaneously both geometrical and mechanical parameters for skin and stiffeners at each characteristic scale (mesoscopic and macroscopic ones). In this background, at the first level (macroscopic scale) the goal is to find the optimum value of geometric and mechanical design variables of the panel minimising its mass and meeting the set of imposed constraints. The second-level problem focuses on the laminate mesoscopic scale and aims at finding at least one stacking sequence (for each laminate composing the panel) meeting the geometrical and mechanical parameters provided by the first-level problem. The MS2L optimisation approach is based on the polar formalism to describe the macroscopic behaviour of the composites and on a special genetic algorithm to perform optimisation calculations. The quality of the optimum configurations is investigated, a posteriori, through a refined finite element model of the stiffened panel making use of elements with different kinematics and accuracy in the framework of the Carrera’s Unified Formulation (CUF).
       
  • Experimental and numerical studies on seismic performance of traditional
           style steel-concrete composite frame
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Liangjie Qi, Jianyang Xue, Lei Zhai, Xuan Zhao, Roberto T. Leon In order to study the seismic performance of a Chinese traditional style steel-concrete composite frame, a half-scale prototype was designed for a region with intensity seven in the Chinese seismic design code. In the experiment, the El Centro, Taft, Lanzhou and Wenchuan ground motions with different peak accelerations (0.035 g, 0.1 g, 0.22 g, 0.4 g) were used to simulate earthquakes of different characteristics and intensities. The displacement response, restoring force and acceleration response of the measured structure were analyzed, and the hysteresis characteristics, failure mechanism, deformability and energy dissipation capacity of the model were quantified. The results show that the damage caused is concentrated in the beams and at the transition zone between the upper and lower column as evidenced by noticeable pinching of the hysteresis curves. The ultimate story drift reached is about 1/157–1/153 (0.65%), satisfying the elastic-plastic limits in the code. At a peak acceleration of 0.4 g, the stiffness of the specimen is 66% lower than that at a peak acceleration of 0.035 g. The most obvious structural response is under the excitation of El Centro wave, while the smallest is under the action of Wenchuan ground motion. The finite element software SAP2000 was used to analyze the failure of the specimen, the displacement time history curve and sequence of the plastic hinges. The calculated values of the finite element are in reasonable agreement with the experimental values, which can supply some reference to the practical engineering application.
       
  • Double lap shear test on steel fabric reinforced cementitious matrix
           (SFRCM)
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): F.O. Falope, L. Lanzoni, A.M. Tarantino The present work deals with the experimental characterization of the mechanical bond behaviour of a galvanized steel fabric reinforced cementitious matrix (SFRCM) laminated on concrete support. The specimens, made of two low strength concrete blocks connected with a galvanized steel fabric embedded in a geo-polymeric mortar layer, have been tested according to double lap test (DLT) set-up. Six different groups of specimens have been tested varying both the lamination length and the steel fabric density. In order to reproduce the load-slip or bond-slip curves, a tri-linear bond slip model together with its parameters identification has been proposed.For some specimens, the slip profile and the slip distribution have been analysed and split into the substrate laminate slip and inner laminate layers slip. This distinction has been used as a measure of the fabric-matrix compatibility. In addition, the effect induced by the rigid blocks rotation occurred during the DLT has been argued. The DIC optical system monitoring has been used to asses both the force-slip distribution and the crack opening displacement (COD).
       
  • Optimal form and size characterization of planar isotropic petal-shaped
           auxetics with tunable effective properties using IGA
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Zhen-Pei Wang, Leong Hien Poh Focusing on planar isotropic petal-shaped auxetics, an isogeometric design framework is presented to achieve tunable effective properties. Specifically, the design framework includes (i) a NURBS-based parametric modelling scheme that characterizes petal-shaped auxetics with a small number of design variables; (ii) a systematic consideration of petal form, component widths and base material properties; (iii) a semi-analytical sensitivity analysis method based on material derivatives; and (iv) constraints for effective stiffness and target Poisson ratio. Three cases are considered: Case A with the same component width, Case B with different component widths, and Case C for composite designs with multiple base materials. For each case, a design limit curve is obtained for the effective Poisson ratio over a range of effective stiffness constraints, to give a quick overview on the properties attainable for each design setting. The optimization framework is next demonstrated for designing composite petal-shaped auxetics with target effective properties.
       
  • An experimental study on cracking and deformations of tensile concrete
           elements reinforced with multiple GFRP bars
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Viktor Gribniak, Arvydas Rimkus, Lluis Torres, David Hui Although different setups have been developed for analysis of the serviceability properties (cracking and deformations) of reinforced concrete elements, tensile tests are remaining the most often used testing layouts. Recent studies, however, have revealed noticeable limitations of the traditional tests of concrete prisms reinforced with a centre bar. The essential aspect responsible for adequate interpretation of the test outcomes could be addressed to inter-correlation of the basic cross-section parameters, i.e. bar diameter, reinforcement ratio, and cover depth. Furthermore, the test equipment has a limited possibility comparing outcomes of the tensile prisms reinforced with bars made of steel and fibre reinforced polymer materials. To solve these problems, a special equipment for the anchorage of multiple bars has been developed. This manuscript presents and discusses the tests results of 16 prismatic specimens reinforced with steel and glass fibre reinforced polymer (GFRP) bars provided by different producers. At the same deformation range of reinforcement, almost identical crack distances are characteristic of the prisms reinforced with steel and GFRP bars with similar axial stiffness. This result enables formulating a hypothesis that crack spacing in tensile elements of equivalent axial stiffness is predominantly dependent on geometry of the concrete and, particularly, on the cover depth.
       
  • Dynamic fracture analysis of functionally graded materials under thermal
           shock loading by using the radial integration boundary element method
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Baojing Zheng, Yang Yang, Xiaowei Gao, Ch. Zhang A coupled thermoelastic radial integration boundary element method is applied to analyze the dynamic fracture mechanics of functionally graded materials (FGMs) subjected to the thermal shock loadings. The dynamic stress intensity factor (DSIF) of the crack tip is defined by the crack open displacement (COD) near the crack tip. The effects of material gradating direction versus crack direction and the coupling effects on the stress intensity factor are studied for two- and three-dimensional crack structures. The results demonstrate that the present method is very accuracy and efficiency to analyze the dynamic fracture mechanics for the cracked FGMs. The research also provides a theoretical basis for engineering design, and can extend the application range of the boundary element method.
       
  • Strain rate effects on the intralaminar fracture toughness of composite
           laminates subjected to tensile load
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Luiz Fernando Martins Leite, Bruno Martins Leite, Vitor Luiz Reis, Nubia Nale Alves da Silveira, Maurício Vicente Donadon This paper presents a numerical and experimental study on the intralaminar tensile fracture toughness of carbon fiber reinforced composite subjected to high strain rates. As there is no standardized testing procedures for intralaminar fracture toughness characterization of composites at high strain rates, there is a clear need to design specimen geometries, testing apparatus and data reduction schemes that allows the characterization of the fracture toughness of composites in the dynamic regime. Initially numerical studies were performed based on finite element simulations in order to investigate the viability of its construction for different testing configurations to characterize the intralaminar toughness of composite laminates. A comparative study is presented showing the advantages and disadvantages of each testing configuration. A new data reduction scheme based on modifications in the ASTM standard, accounting for material anisotropy and specimen finite geometry effects is suggested. Experimental tests were carried out, using the proposed specimen configuration at different strain rates in order to investigate the strain rate effects using a modified version of the Split Hopkinson Pressure Bar. Fractography analyses using Scanning Electron Microscopy(SEM) have been also performed in order to investigate the strain rate effects on the failures mechanisms of the composite material studied herein.
       
  • A reduced micromorphic model for multiscale materials and its applications
           in wave propagation
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Mohamed Shaat In this study, a reduced micromorphic model for multiscale materials is developed. In the context of this model, multiscale materials are modeled with deformable microstructures. The deformation energy is formed depending on microstrain and macroscopic strain residual fields. The constitutive equations according to the reduced micromorphic model only depend on eight material coefficients for linear elastic materials. These material coefficients are related to the material micro/macro-stiffnesses and the material’s microstructural features. The wave dispersions in multiscale materials are then derived according to the reduced micromorphic model. It is revealed that this model can reflect nine dispersion curves (three acoustic modes and six optics) for a two-scale material. To demonstrate the effectiveness of the proposed model, the wave propagation characteristics, the band structure, and the absolute bandgap features of phononic materials are investigated. It is demonstrated that the reduced micromorphic model can effectively reflect the increase in the bandgap width with the increase in the filling factor in a composite phononic material with square lattices.
       
  • A computationally efficient model to predict the uniaxial tensile loading
           response for dry woven fabrics
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Yabin Yang, Pan Zeng Woven structure is an essential component widely used in composite materials, bio-materials and mechanical metamaterials. The mechanical response of the dry woven fabric, which is widely used as reinforcement in composite materials is studied in the present paper. Typically, for the dry woven fabric, the warp and weft yarns are weaved with each other. Each warp or weft yarn also consists of large amounts of small filaments. Because of this multiscale nature, a model that can predict the material response as a function of the underlying structure is important for the design of the dry woven fabric. Hence, a computationally efficient model to simulate the uniaxial tensile loading response for dry woven fabrics is proposed. The proposed model is able to predict the macroscopic loading-deformation response, the effective in-plane Poisson’s effect and the deformation of the thickness by taking into account the influence of the filaments, the weaving pattern and the surface contact at the crossover of the yarns. The accuracy of the model is validated by a digital image correlation (DIC) experiment. For the weaved yarns, complex yarn geometries can be easily modelled and different yarn curve assumptions can be conveniently incorporated in the proposed model. The high computational efficiency of the model makes it potentially helpful for designing woven materials with high mechanical performance.
       
  • Crushing and energy absorption of density-graded foam-filled square
           columns: Experimental and theoretical investigations
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Xuehui Yu, Qinghua Qin, Jianxun Zhang, Siyuan He, Chunping Xiang, Mingshi Wang, T.J. Wang The static axial crushing and energy absorption of density-graded aluminum foam-filled square metal columns are experimentally and theoretically investigated. Typical deformation modes are observed in experiments, such as symmetric, asymmetric, extension and rupture modes. Theoretical analysis is carried out and the predictions are in good agreement with the experimental results. The effects of gradient pattern, density difference, average density of foam, and wall thickness on the crushing of foam-filled columns are discussed. It is shown that the density-graded aluminum foam-filled square metal column is a novel topological structure with higher energy absorption, higher load-carrying capacity and much higher crushing force efficiency.
       
  • Dynamic response of viscoelastic functionally graded hollow cylinder
           subjected to thermo-mechanical loads
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Ahmad Akbari, Akbar Bagri, Sundararajan Natarajan In this paper, the dynamic response of functionally graded viscoelastic hollow cylinder subjected to thermo-mechanical loads is studied using the meshless local Petrov-Galerkin method. The material is assumed to be graded in the radial direction with aluminum as viscoelastic constituent and alumina as the elastic constituent. The macroscopic viscoelastic properties are evaluated using the rule of mixtures and the inverse rule of mixtures, whilst that of the cylinder is computed by employing the Mori-Tanaka homogenization scheme. A systematic parametric study is carried out to bring out the influence of material gradient index, the viscoelastic properties and the boundary conditions on the dynamic/transient response of the cylinder.
       
  • Post-fire residual properties of GFRP reinforced concrete slabs: A
           holistic investigation
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Hamzeh Hajiloo, Mark F. Green This paper provides critical data regarding the post-fire residual strength of Glass Fibre Reinforced Polymer (GFRP) reinforced concrete slabs. The residual tensile and bond strength of three types of GFRP reinforcing bars and the post-fire residual strength of a GFRP reinforced concrete slab are examined. For residual tensile strength, GFRP bars with a nominal diameter of 16 mm are exposed to temperatures up to 450 °C and tested after 24 h at room temperature. After 24 h, the specimens are loaded to failure at room temperature. For residual bond strength, pullout specimens are heated under various sustained load values. Finally, a full-scale GFRP reinforced concrete slab is tested at room temperature to evaluate the post-fire residual capacity after exposure to three hours of a standard fire. The residual tensile test results show that the bars that were exposed to 400 °C recovered at least 45% of the original strength while the residual bond strength is approximately 40% for pullout specimens that had experienced 300 °C. The post-fire residual strength of the slab is 68% of its room temperature flexural design strength with the bond loss at the ends of the slab being the governing mode of failure.
       
  • Refill friction stir spot welding of 7075-T6 aluminium alloy single-lap
           joints with polymer sealant interlayer
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Andrzej Kubit, Dawid Wydrzynski, Tomasz Trzepiecinski With the addition of a sealant interlayer, 7075-T6 aluminium alloy sheets were refill friction stir spot welded (RFSSW). Two sealants were used in the investigations: phenol-formaldehyde resin-based adhesive and epoxy resin-based tape. Single-lap RFSSW joints were made in 0.8- and 1.6-mm-thick sheets, which corresponds to the actual thicknesses of welded stringer of aircraft skin. The welding of the sheets with polymeric interlayer lowered the tensile pure/shear load capacity of the joint from approximately 9% to 28%, according to the variant of sealant application. However, the polymer interlayer increases considerably the protection of the weld against the corrosion environment. Considering that the main indicator of joint quality is a tight interlayer of sealant between the faces of joined sheets and simultaneously a minimum degree of imperfection induced in the joint microstructure by sealant material, it can be concluded that the most advantageous joint variant is that with a single interlayer of epoxy-based tape.
       
  • An efficient approach to investigate the post-buckling behaviors of
           sandwich structures
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Jongchol Choe, Qun Huang, Jie Yang, Heng Hu In this paper, we propose an efficient and accurate approach to investigate the post-buckling behavior of sandwich structures. In this framework, a novel one-dimensional layer-wise model using Euler-Bernoulli beam theory in the skins and higher-order kinematics in the core is proposed. The resulting nonlinear governing equations are then solved by the Asymptotic Numerical Method (ANM) with a bifurcation indicator, which is more reliable and efficient than the classical iterative methods, e.g., Newton-Raphson method, in terms of detecting critical points and computing bifurcated branches. Several numerical tests, i.e., global buckling, local wrinkling and global-local-coupling instability phenomena of sandwich beams, are performed and the results show that the proposed approach is able to efficiently and precisely characterize the critical loads and the post-buckling behaviors of sandwich structures. Finally, the effect of three aspects, i.e., kinematics, strain-displacement relationships and interpolation functions on the computational accuracy of predicting these instability phenomena are investigated.
       
  • Behavior of RC beams flexurally strengthened with NSM CFRP laminates
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): S.J.E. Dias, J.A.O. Barros, W. Janwaen An experimental program was carried out to investigate the behavior of RC beams flexurally strengthened using the NSM technique with CFRP laminates. Four beams were tested, a reference beam without CFRP, and three beams flexurally strengthened using different percentage of laminates. The experimental results show that NSM CFRP laminates is an effective solution to increase cracking, yielding and maximum loads of beams failing in bending. Furthermore, the high tensile strength of the CFRP was effectively mobilized. By increasing the CFRP percentage, the load carrying capacity of the NSM beams increased, while the ductility level decreased. Taking into account the experimental results, the predictive performance of the analytical formulation proposed by the ACI was assessed considering two methodologies to determine the maximum strain that can be applied to the CFRP: i) the ACI proposal; ii) the equation proposed by Barros et al. (2007). ACI formulation provides safe results by using both methodologies, but the Barros et al. equation ensures better predictions. A numerical strategy was used to evaluate the load–deflection relationship of the tested beams and to highlight the influence of the longitudinal bars percentage, the CFRP percentage and the concrete strength on the NSM flexural strengthening effectiveness of RC beams.
       
  • The impact of weak interfacial bonding strength on mechanical properties
           of metal matrix – Ceramic reinforced composites
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Dariusz M. Jarząbek In this work the influence of weak interface between particles and matrix on mechanical properties of metal matrix – ceramic reinforced composites is studied. Firstly, the samples made of coelectrodeposited Ni-SiC composites with 10% of SiC with poor interface bonding have been prepared. Furthermore, the tensile tests of samples have been performed. The determined Young’s modulus was equal to 67 ± 8 GPa and the ultimate tensile strength to 230 ± 15 MPa. It is assumed that the very weak interface is the reason for the poor mechanical properties of the created material. In order to confirm the assumption and get the necessary parameters for the numerical model, the measurements of the normal and shear interfacial bonding strength of the interface have been performed. The measured normal interfacial bonding strength is equal to 0.1 ± 0.03 MPa and the interfacial shear strength is equal to 4.9 ± 0.2 MPa. The experimental results have been confirmed qualitatively by the computer simulations. Representative Volume Element has been created and modelled by the Finite Element Method with cohesive zone elements. The computer simulations result in the Young’s modulus values from 119 GPa up to 126 GPa.
       
  • Bloch wave filtering in tetrachiral materials via mechanical tuning
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): F. Vadalà, A. Bacigalupo, M. Lepidi, L. Gambarotta The periodic cellular topology characterizing the microscale structure of a heterogeneous material may allow the finest functional customization of its acoustic dispersion properties. The paper addresses the free propagation of elastic waves in micro-structured cellular materials. Focus is on the alternative formulations suited to describe the wave propagation in the material, according to the classic canons of solid or structural mechanics. Adopting the centrosymmetric tetrachiral microstructure as prototypical periodic cell, the frequency dispersion spectrum resulting from a synthetic lagrangian beam-lattice formulation is compared with its counterpart derived from different continuous models (high-fidelity first-order heterogeneous and equivalent homogenized micropolar continuum). Asymptotic perturbation-based approximations and numerical spectral solutions are cross-validated. Adopting the low-frequency band gaps of the material band structures as functional targets, parametric analyses are carried out to highlight the descriptive limits of the synthetic models and to explore the enlarged parameter space described by high-fidelity models. The final tuning of the mechanical properties of the cellular microstructure is employed to successfully verify the wave filtering functionality of the tetrachiral material.
       
  • FRCM/internal transverse shear reinforcement interaction in shear
           strengthened RC beams
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Tadesse G. Wakjira, Usama Ebead This paper presents a study on the efficacy of a shear strengthening technique utilizing fabric reinforced cementitious matrix (FRCM) systems for beams with and without internal transverse shear reinforcement (ITSR) within the critical shear span (CSS). The paper focuses on the FRCM/ITSR interaction, experimentally and analytically. Three different FRCM fabric types were used; namely, glass, carbon and polyparaphenylene benzobisoxazole (PBO). The test matrix consisted of fourteen medium-scale RC beams prepared and tested to fail in shear. The test results indicated a clear influence of the ITSR within the CSS on the gain in the ultimate load carrying capacity (Pu) of the beams. The FRCM strengthening system has enhanced the shear strength of the beams. With regard to the FRCM fabric type, carbon FRCM was the most effective of all in terms of the gain in Pu of the strengthened beams. Moreover, the beams strengthened with continuous strengthening configuration intuitively performed better than those strengthened with discontinuous configuration. A simplified compression field theory (SCFT) model was used for predicting the ultimate load carrying capacity of the beams. This model features two important contributions; namely, considering the effect of FRCM strengthening and accounting for the critical shear span to depth ratio.
       
  • Eccentric low-velocity impact on fiber-metal laminates under in-plane
           loading using unified zigzag theory
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Mehran Ghalami-Choobar, Gholamhossein Liaghat, Mojtaba Sadighi, Hamed Ahmadi This paper investigates the eccentric low-velocity impact of Fiber metal laminates (FMLs) subjected to spherical projectile using a unified Zig-Zag plate theory. The presented zig-zag plate theory enforces transverse shear stress continuity through the thickness and can be reduced to conventional plate theories using appropriate shape function. The governing equations and suitable boundary conditions are obtained using the principle of minimum total potenital energy. Runge-Kutta method is employed to solve initial value problem resulted by the method of Ritz. The present model is validated by comparison and good agreement between its results and those of reports in open literature. Influence of various specifications of impact phenomenon such as laminate thickness, projectile radius, projectile velocity, in-plane load and eccentricity parameter is examined on deflection and contact force time history. The obtained results indicate that continuity of transverse shear stress is required to achieve accurate contact force even for moderately thin FMLs.
       
  • Effect of resin matrix on the strength of an AZ31 Mg alloy-CFRP joint made
           by the hot metal pressing technique
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Barton Mensah Arkhurst, Mokyoung Lee, Jeoung Han Kim This study investigated the effect of two types of carbon fiber reinforced plastics (CFRPs) with different matrices, on the strength of a metal alloy–plastic composite joint made by the hot metal pressing (HMP) technique. One set of experiments was carried out with a PAN-type CFRP with a thermoplastic polyurethane (TPU) matrix, and the other with a PAN-type CFRP with a polyamide 6 (PA6) matrix. Both matrices were joined with either as-received or annealed AZ31 Mg-alloy sheets processed at different annealing durations to produce oxide layers on the alloy sheets. Due to the complete suppression of CFRP-resin decomposition at its joint interface, the CFRP with a PA6 matrix exhibited superior joint strength as compared to the TPU-matrix CFRP, which showed partial suppression of the CFRP-resin decomposition and bubble formation, with complete suppression characterized by microcracking at its joint interface. A reaction between C and MgO was observed at the joint interface for the TPU-CFRP but not for the PA6-CFRP. The melting/decomposition temperature of the matrix materials and the influence of the oxide layer on the conduction of heat between the materials were the key determinants of the AZ Mg alloy-CFRP joint strength.
       
  • Elastoplastic CDM model based on Puck’s theory for the prediction of
           mechanical behavior of Fiber Reinforced Polymer (FRP) composites
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): I. Ud Din, P. Hao, G. Franz, S. Panier In this paper, the plane stress version of the Puck’s failure theory is used as an indicator of the intra-laminar meso-damage initiation. The thermodynamically consistent damage evolution law is defined to accumulate the damage leading to the subsequent stiffness degradation coupled with the isotropic hardening plasticity. The model is formulated in incremental form keeping in view the implementation by following the plasticity theory which is later used in the Return Mapping Algorithm (RMA). In the implicit scheme based on the Newton-Raphson approach, the consistent tangent operator is derived for the current model. The developed model has been implemented in ABAQUS/Standard via UMAT subroutine in a strain-driven problem where strain tensor is provided as an independent argument into the solution scheme. The non-linear mechanical behavior and ultimate failure of Carbon Fiber Reinforced Polymers (CFRPs) laminates are predicted for the small strain time-independent boundary value problem. The results are compared with the experimental results collected from the previously published literature which exhibit better correspondence.
       
  • On the static strength of aluminium and carbon fibre aircraft lap joint
           repairs
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Siddharth Pitta, Victor de la Mora Carles, Francesc Roure, Daniel Crespo, Jose I. Rojas The behaviour of various aircraft lap joint repair configurations is investigated experimentally and numerically under static loading. The lap joints consist of aluminium alloy (AA) 2024-T3 substrates repaired with twin single-sided AA 2024-T3 or Carbon Fibre Reinforced Epoxy (CFRE) doublers. Pure riveted, pure bonded and hybrid (riveted and bonded) joints of metal–metal and metal–composite configurations are investigated. From experimental results, joints with adhesive bond showed nearly 5 times higher average strength than pure riveted joints, while hybrid joints performed better than riveted and bonded joints because of higher stiffness. On the other hand, hybrid metal–metal joint has 70% higher average strength compared to hybrid metal–composite joint. Rivet-shear has caused failure of riveted joints, and adhesive failure is observed in pure bonded joints. Hybrid joints with metal doublers have failed initially due to adhesive failure and later rivet shear. Interestingly, net-section failure is observed in composite doublers with breakage of doublers due to the presence of holes in the doublers. Experimental results are complimented with numerical analysis using commercial finite element code ABAQUS. Load–displacement curves obtained from the numerical results are in good agreement with experiments with a marginal error of 2%. In addition to load–displacement curves, a detailed stress analysis is performed numerically on metal–metal and metal-composite joints under riveted, bonded and hybrid configurations to study stress distribution on substrate and doublers. Numerical analysis showed hybrid and bonded joints have lower stresses in substrate and doublers compared to the riveted joints. Bonded joints have smoother load transfer due to the adhesive spread over a larger area. And finally, Stress Intensity Factors (SIFs) are performed numerically for unreinforced and reinforced metal substrate with crack length of 1, 5 and 10 mm with metal and composite doublers under riveted and bonded configuration. For crack of 10 mm, 35% reduction in SIFs is observed for reinforced substrate with bonded metal or composite doublers compared to unreinforced cracked substrate.
       
  • 3D explicit finite element analysis of tensile failure behavior in
           adhesive-bonded composite single-lap joints
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Jinxin Ye, Ying Yan, Jie Li, Yang Hong, Ziyang Tian The tensile failure behavior in adhesive-bonded composite single-lap joints with different overlap lengths is investigated through experiments and various three-dimensional (3D) explicit finite element methods (FEMs). Different failure modes are observed in different overlap lengths. Three parameterized finite element models are developed to discuss the accuracy and applicability of the 3D explicit FEMs based on different modeling strategies and improved failure criteria. All criteria are programmed with the explicit user subroutines employing element deletion to avoid convergence problems caused by element distortion. The load-displacement curves predicted by these models are consistent with the experimental results, while the prediction of failure morphology depends on model types. The models neglecting interface elements cannot simulate the delamination when cohesive zone models (CZMs) are adopted to predict adhesive failure. The influence of CZMs on delamination is analyzed comprehensively to address this problem. Analysis of stress distribution in an overlap of a length of 10 mm indicates that the peak stress of the adhesive layer occurs on the overlap ends along the axial direction, coinciding with implicit results.
       
  • Cyclic flexural behavior of hybrid SMA/steel fiber reinforced concrete
           analyzed by optical and acoustic techniques
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Muhammad M. Sherif, Evelina M. Khakimova, Jonathon Tanks, Osman E. Ozbulut Superelastic shape memory alloys (SMAs) are smart materials that can recover 6–8% elastic strains due to their phase transformation. SMAs also possess unique characteristics such as good energy dissipation, excellent re-centering capabilities and corrosion resistance. Recent studies have incorporated the use of superelastic SMA fibers in cementitious composites to achieve re-centering and crack-closing capabilities. Consequently, it is important to investigate the performance of fiber reinforced concrete (FRC) members under cyclic loading. This study investigates the use of hybrid steel/SMA fibers as reinforcement in concrete members subjected to cyclic flexural loading. Digital image correlation (DIC) was used to monitor the full field displacements and strains of the concrete beam specimens. Fiber density and statistical spatial point pattern functions were used to assess the fiber distribution. Two acoustic emission sensors were attached to each side of the concrete specimens to characterize crack development. A correlation between the crack width propagation and cumulative energy captured by the acoustic emission sensors was established. Results showed that the hybrid specimen with equal fiber volume ratios for steel and SMA fibers exhibit a lower mid-span deflection and smaller crack width.
       
  • Confinement path-dependent analytical model for FRP-confined concrete and
           concrete-filled steel tube subjected to axial compression
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Peng Chen, Yuyin Wang, Changyong Liu In composite component, confined concrete is widely used in civil engineering due to its excellent performance, such as high compressive strength and good plasticity. In this study, an actively-confined concrete model is developed using current published models and test data, the stress-strain behavior of concrete in active confinement and fiber-reinforced polymer confinement are compared, then the influence of loading path on concrete is quantified. An analytical model is developed to predict the mechanical behavior of confined concrete columns, and validated using previously published test results. The analytical model is found to provide satisfactory predictions in short concrete columns confined by FRP or steel tubes.
       
  • Topology optimization for continuous and discrete orientation design of
           functionally graded fiber-reinforced composite structures
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Jaewook Lee, Dongjin Kim, Tsuyoshi Nomura, Ercan M. Dede, Jeonghoon Yoo This paper presents a topology optimization method for the sequential design of material layout and fiber orientation in functionally graded fiber-reinforced composite structures. Specifically, the proposed method can find the optimal structural layout of matrix and fiber materials together with optimal discrete fiber orientations. In this method, an orientation design variable in the Cartesian coordinate system is employed with a conventional density design variable. The orientation design variable controls not only the fiber orientation, but also fiber volume fraction. The fiber volume fraction control can be used to relax the orientation design problem and simultaneously design a functionally graded structural layout of fiber material. To avoid intermediate fiber orientations and achieve discrete fiber orientation design, a penalization scheme is applied to the orientation design variable. For solving the optimization problem which involves multiple design variables such as the density variable, fiber orientation variable, and target discrete orientation set, a three-step sequential optimization procedure is proposed. In this procedure, the result for each step provides the isotropic design, continuous fiber orientation design, and functionally graded discrete orientation design, respectively. To validate the effectiveness of the proposed approach, numerical examples for structural compliance minimization and compliant mechanism design are provided.
       
  • Formulation of a consistent pressure-dependent damage model with fracture
           energy as input
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): Azam Arefi, Frans P. van der Meer, Mohammad Reza Forouzan, Mohammad Silani Micromechanical simulation of composite material failure requires a pressure-dependent failure model for the polymeric matrix. Available pressure-dependent damage formulations assume a certain shape of the stress-strain law under uniaxial loading. However, upon close inspection none of the available formulations is able to reproduce the assumed shape. This implies that input values for the fracture energy cannot be recovered exactly.In this paper, a new methodology for developing consistent pressure-dependent damage models for polymeric materials is presented. Using this method the predefined shape of the stress-strain relation of an element with localized deformation under uniaxial tension can be exactly reproduced which enables further to recover the exact amount of energy dissipation consistent with the input toughness. The methodology is demonstrated for two different softening laws, namely linear and exponential softening. These models are applied to the damage analysis of unidirectional continuous fiber-reinforced composites. The formulation is validated by simulation of a test for Mode-I fracture energy characterization and comparing the load-displacement response with that obtained with cohesive elements.
       
  • Fundamental frequency of a composite anisogrid lattice cylindrical panel
           with clamped edges
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): A.V. Lopatin, E.V. Morozov, A.V. Shatov A derivation and validation of an analytical formula for the calculation of the fundamental frequency of a composite anisogrid lattice cylindrical panel with clamped edges is presented in this paper. Free vibration analysis is performed based on the continuous model of a lattice structure using the equations of engineering theory of orthotropic cylindrical shells. The problem was solved using the Galerkin method in which the displacements of the panel were approximated by the clamped-clamped beam functions. The analytical formula derived from this solution was employed to study the effects of the structural parameters of composite lattice panels on their fundamental frequencies. The results of these parametric analyses were successfully verified by comparisons with the finite-element solutions. It is shown that the analytical model that only takes into account the inertia of the transverse motion of the panel in the direction normal to its surface provides a reasonable estimate of the value of fundamental frequency. It is also demonstrated how the formula works in the calculations delivering the required fundamental frequency when designing the composite lattice panels.
       
  • Bond strength model for near-surface mounted (NSM) FRP bonded joints:
           Effect of concrete edge distance
    • Abstract: Publication date: 1 October 2018Source: Composite Structures, Volume 201Author(s): S.S. Zhang As one of the mainstream topics in the research field of infrastructure application of FRP composites, the near-surface mounted (NSM) fiber-reinforced polymer (FRP) strengthening technique has attracted an increasing attention over the last decade and become an effective alternative to the externally bonded FRP strengthening method. The bond strength (i.e., maximum force that can be developed in the FRP reinforcement) of NSM FRP bonded joints has been extensively studied by worldwide researchers, and several bond strength models have been established. All the existing bond strength models, however, are not able to consider the detrimental effect of insufficient concrete edge distance (i.e., the distance between the groove and the nearer edge of the concrete). To clarify such detrimental effect on the bond strength between NSM FRP strip and concrete, a numerical parametric study, employing a three-dimensional meso-scale model developed by the author for NSM FRP bonded joints, is conducted in the present study. Based on the results from the parametric study, reduction factors are formulated to consider such detrimental effect and a bond strength model incorporating the reduction factors are proposed. The accuracy of the proposed bond strength model is verified with a large test database containing 86 specimens.
       
 
 
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