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  Subjects -> ENGINEERING (Total: 2358 journals)
    - CHEMICAL ENGINEERING (201 journals)
    - CIVIL ENGINEERING (192 journals)
    - ELECTRICAL ENGINEERING (107 journals)
    - ENGINEERING (1240 journals)
    - ENGINEERING MECHANICS AND MATERIALS (394 journals)
    - HYDRAULIC ENGINEERING (56 journals)
    - INDUSTRIAL ENGINEERING (72 journals)
    - MECHANICAL ENGINEERING (96 journals)

ENGINEERING (1240 journals)                  1 2 3 4 5 6 7 | Last

Showing 1 - 200 of 1205 Journals sorted alphabetically
3 Biotech     Open Access   (Followers: 8)
3D Research     Hybrid Journal   (Followers: 19)
AAPG Bulletin     Hybrid Journal   (Followers: 8)
AASRI Procedia     Open Access   (Followers: 14)
Abstract and Applied Analysis     Open Access   (Followers: 3)
Aceh International Journal of Science and Technology     Open Access   (Followers: 2)
ACS Nano     Full-text available via subscription   (Followers: 265)
Acta Geotechnica     Hybrid Journal   (Followers: 7)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 6)
Acta Polytechnica : Journal of Advanced Engineering     Open Access   (Followers: 3)
Acta Scientiarum. Technology     Open Access   (Followers: 3)
Acta Universitatis Cibiniensis. Technical Series     Open Access  
Active and Passive Electronic Components     Open Access   (Followers: 7)
Adaptive Behavior     Hybrid Journal   (Followers: 11)
Adıyaman Üniversitesi Mühendislik Bilimleri Dergisi     Open Access  
Adsorption     Hybrid Journal   (Followers: 4)
Advanced Engineering Forum     Full-text available via subscription   (Followers: 7)
Advanced Science     Open Access   (Followers: 5)
Advanced Science Focus     Free   (Followers: 5)
Advanced Science Letters     Full-text available via subscription   (Followers: 9)
Advanced Science, Engineering and Medicine     Partially Free   (Followers: 7)
Advanced Synthesis & Catalysis     Hybrid Journal   (Followers: 18)
Advances in Calculus of Variations     Hybrid Journal   (Followers: 2)
Advances in Catalysis     Full-text available via subscription   (Followers: 5)
Advances in Complex Systems     Hybrid Journal   (Followers: 6)
Advances in Engineering Software     Hybrid Journal   (Followers: 27)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 15)
Advances in Fuzzy Systems     Open Access   (Followers: 5)
Advances in Geosciences (ADGEO)     Open Access   (Followers: 12)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 21)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 23)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 9)
Advances in Natural Sciences: Nanoscience and Nanotechnology     Open Access   (Followers: 30)
Advances in Operations Research     Open Access   (Followers: 12)
Advances in OptoElectronics     Open Access   (Followers: 5)
Advances in Physics Theories and Applications     Open Access   (Followers: 13)
Advances in Polymer Science     Hybrid Journal   (Followers: 43)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Remote Sensing     Open Access   (Followers: 43)
Advances in Science and Research (ASR)     Open Access   (Followers: 4)
Aerobiologia     Hybrid Journal   (Followers: 2)
African Journal of Science, Technology, Innovation and Development     Hybrid Journal   (Followers: 6)
AIChE Journal     Hybrid Journal   (Followers: 35)
Ain Shams Engineering Journal     Open Access   (Followers: 5)
Akademik Platform Mühendislik ve Fen Bilimleri Dergisi     Open Access   (Followers: 1)
Alexandria Engineering Journal     Open Access   (Followers: 1)
AMB Express     Open Access   (Followers: 1)
American Journal of Applied Sciences     Open Access   (Followers: 26)
American Journal of Engineering and Applied Sciences     Open Access   (Followers: 10)
American Journal of Engineering Education     Open Access   (Followers: 9)
American Journal of Environmental Engineering     Open Access   (Followers: 16)
American Journal of Industrial and Business Management     Open Access   (Followers: 23)
Analele Universitatii Ovidius Constanta - Seria Chimie     Open Access  
Annals of Combinatorics     Hybrid Journal   (Followers: 3)
Annals of Pure and Applied Logic     Open Access   (Followers: 2)
Annals of Regional Science     Hybrid Journal   (Followers: 7)
Annals of Science     Hybrid Journal   (Followers: 7)
Antarctic Science     Hybrid Journal   (Followers: 1)
Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 2)
Applicable Analysis: An International Journal     Hybrid Journal   (Followers: 1)
Applied Catalysis A: General     Hybrid Journal   (Followers: 6)
Applied Catalysis B: Environmental     Hybrid Journal   (Followers: 18)
Applied Clay Science     Hybrid Journal   (Followers: 5)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 11)
Applied Magnetic Resonance     Hybrid Journal   (Followers: 4)
Applied Nanoscience     Open Access   (Followers: 8)
Applied Network Science     Open Access   (Followers: 3)
Applied Numerical Mathematics     Hybrid Journal   (Followers: 5)
Applied Physics Research     Open Access   (Followers: 4)
Applied Sciences     Open Access   (Followers: 3)
Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 4)
Arabian Journal for Science and Engineering     Hybrid Journal   (Followers: 5)
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 5)
Archives of Foundry Engineering     Open Access  
Archives of Thermodynamics     Open Access   (Followers: 8)
Arkiv för Matematik     Hybrid Journal   (Followers: 1)
ASEE Prism     Full-text available via subscription   (Followers: 3)
Asia-Pacific Journal of Science and Technology     Open Access  
Asian Engineering Review     Open Access  
Asian Journal of Applied Science and Engineering     Open Access   (Followers: 1)
Asian Journal of Applied Sciences     Open Access   (Followers: 2)
Asian Journal of Biotechnology     Open Access   (Followers: 8)
Asian Journal of Control     Hybrid Journal  
Asian Journal of Current Engineering & Maths     Open Access  
Asian Journal of Technology Innovation     Hybrid Journal   (Followers: 8)
Assembly Automation     Hybrid Journal   (Followers: 2)
at - Automatisierungstechnik     Hybrid Journal   (Followers: 1)
ATZagenda     Hybrid Journal  
ATZextra worldwide     Hybrid Journal  
Australasian Physical & Engineering Sciences in Medicine     Hybrid Journal   (Followers: 1)
Australian Journal of Multi-Disciplinary Engineering     Full-text available via subscription   (Followers: 2)
Autonomous Mental Development, IEEE Transactions on     Hybrid Journal   (Followers: 9)
Avances en Ciencias e Ingeniería     Open Access  
Balkan Region Conference on Engineering and Business Education     Open Access   (Followers: 1)
Bangladesh Journal of Scientific and Industrial Research     Open Access  
Basin Research     Hybrid Journal   (Followers: 5)
Batteries     Open Access   (Followers: 6)
Bautechnik     Hybrid Journal   (Followers: 1)
Bell Labs Technical Journal     Hybrid Journal   (Followers: 26)
Beni-Suef University Journal of Basic and Applied Sciences     Open Access   (Followers: 4)
BER : Manufacturing Survey : Full Survey     Full-text available via subscription   (Followers: 1)
BER : Motor Trade Survey     Full-text available via subscription  
BER : Retail Sector Survey     Full-text available via subscription   (Followers: 1)
BER : Retail Survey : Full Survey     Full-text available via subscription   (Followers: 1)
BER : Survey of Business Conditions in Manufacturing : An Executive Summary     Full-text available via subscription   (Followers: 2)
BER : Survey of Business Conditions in Retail : An Executive Summary     Full-text available via subscription   (Followers: 3)
Bhakti Persada : Jurnal Aplikasi IPTEKS     Open Access  
Bharatiya Vaigyanik evam Audyogik Anusandhan Patrika (BVAAP)     Open Access   (Followers: 1)
Biofuels Engineering     Open Access   (Followers: 1)
Biointerphases     Open Access   (Followers: 1)
Biomaterials Science     Full-text available via subscription   (Followers: 10)
Biomedical Engineering     Hybrid Journal   (Followers: 15)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 13)
Biomedical Engineering Letters     Hybrid Journal   (Followers: 5)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 19)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 35)
Biomedical Engineering: Applications, Basis and Communications     Hybrid Journal   (Followers: 5)
Biomedical Microdevices     Hybrid Journal   (Followers: 9)
Biomedical Science and Engineering     Open Access   (Followers: 4)
Biomedizinische Technik - Biomedical Engineering     Hybrid Journal  
Biomicrofluidics     Open Access   (Followers: 4)
BioNanoMaterials     Hybrid Journal   (Followers: 2)
Biotechnology Progress     Hybrid Journal   (Followers: 39)
Boletin Cientifico Tecnico INIMET     Open Access  
Botswana Journal of Technology     Full-text available via subscription   (Followers: 1)
Boundary Value Problems     Open Access   (Followers: 1)
Brazilian Journal of Science and Technology     Open Access   (Followers: 2)
Broadcasting, IEEE Transactions on     Hybrid Journal   (Followers: 10)
Bulletin of Canadian Petroleum Geology     Full-text available via subscription   (Followers: 15)
Bulletin of Engineering Geology and the Environment     Hybrid Journal   (Followers: 14)
Bulletin of the Crimean Astrophysical Observatory     Hybrid Journal  
Cahiers, Droit, Sciences et Technologies     Open Access  
Calphad     Hybrid Journal  
Canadian Geotechnical Journal     Hybrid Journal   (Followers: 31)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 42)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 6)
Case Studies in Thermal Engineering     Open Access   (Followers: 5)
Catalysis Communications     Hybrid Journal   (Followers: 6)
Catalysis Letters     Hybrid Journal   (Followers: 2)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 7)
Catalysis Science and Technology     Free   (Followers: 8)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysis Today     Hybrid Journal   (Followers: 7)
CEAS Space Journal     Hybrid Journal   (Followers: 2)
Cellular and Molecular Neurobiology     Hybrid Journal   (Followers: 3)
Central European Journal of Engineering     Hybrid Journal  
CFD Letters     Open Access   (Followers: 6)
Chaos : An Interdisciplinary Journal of Nonlinear Science     Hybrid Journal   (Followers: 2)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 3)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 2)
Chinese Journal of Engineering     Open Access   (Followers: 2)
Chinese Science Bulletin     Open Access   (Followers: 1)
Ciencia e Ingenieria Neogranadina     Open Access  
Ciencia en su PC     Open Access   (Followers: 1)
Ciencias Holguin     Open Access   (Followers: 2)
CienciaUAT     Open Access   (Followers: 1)
Cientifica     Open Access  
CIRP Annals - Manufacturing Technology     Full-text available via subscription   (Followers: 11)
CIRP Journal of Manufacturing Science and Technology     Full-text available via subscription   (Followers: 13)
City, Culture and Society     Hybrid Journal   (Followers: 20)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Clean Air Journal     Full-text available via subscription   (Followers: 1)
Coal Science and Technology     Full-text available via subscription   (Followers: 3)
Coastal Engineering     Hybrid Journal   (Followers: 11)
Coastal Engineering Journal     Hybrid Journal   (Followers: 5)
Coatings     Open Access   (Followers: 4)
Cogent Engineering     Open Access   (Followers: 2)
Cognitive Computation     Hybrid Journal   (Followers: 4)
Color Research & Application     Hybrid Journal   (Followers: 2)
COMBINATORICA     Hybrid Journal  
Combustion Theory and Modelling     Hybrid Journal   (Followers: 14)
Combustion, Explosion, and Shock Waves     Hybrid Journal   (Followers: 13)
Communications Engineer     Hybrid Journal   (Followers: 1)
Communications in Numerical Methods in Engineering     Hybrid Journal   (Followers: 2)
Components, Packaging and Manufacturing Technology, IEEE Transactions on     Hybrid Journal   (Followers: 28)
Composite Interfaces     Hybrid Journal   (Followers: 7)
Composite Structures     Hybrid Journal   (Followers: 271)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 207)
Composites Part B : Engineering     Hybrid Journal   (Followers: 246)
Composites Science and Technology     Hybrid Journal   (Followers: 182)
Comptes Rendus Mécanique     Full-text available via subscription   (Followers: 2)
Computation     Open Access  
Computational Geosciences     Hybrid Journal   (Followers: 15)
Computational Optimization and Applications     Hybrid Journal   (Followers: 7)
Computational Science and Discovery     Full-text available via subscription   (Followers: 2)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 8)
Computer Science and Engineering     Open Access   (Followers: 19)
Computers & Geosciences     Hybrid Journal   (Followers: 30)
Computers & Mathematics with Applications     Full-text available via subscription   (Followers: 8)
Computers and Electronics in Agriculture     Hybrid Journal   (Followers: 5)
Computers and Geotechnics     Hybrid Journal   (Followers: 11)
Computing and Visualization in Science     Hybrid Journal   (Followers: 6)
Computing in Science & Engineering     Full-text available via subscription   (Followers: 33)
Conciencia Tecnologica     Open Access  
Concurrent Engineering     Hybrid Journal   (Followers: 3)
Continuum Mechanics and Thermodynamics     Hybrid Journal   (Followers: 8)
Control and Dynamic Systems     Full-text available via subscription   (Followers: 9)
Control Engineering Practice     Hybrid Journal   (Followers: 43)
Control Theory and Informatics     Open Access   (Followers: 8)
Corrosion Science     Hybrid Journal   (Followers: 25)

        1 2 3 4 5 6 7 | Last

Journal Cover Composite Structures
  [SJR: 2.408]   [H-I: 92]   [271 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0263-8223
   Published by Elsevier Homepage  [3176 journals]
  • Modular assembly of water-retaining walls using GFRP hollow profiles:
           Components and connection performance
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Wahid Ferdous, Yu Bai, Ahmed D. Almutairi, Sindu Satasivam, Juri Jeske
      This study proposes and examines a new structural retaining wall system using pultruded glass fibre reinforced polymer (GFRP) composites. The flexural behaviour of the two section types (double-H-planks and round-piles) are investigated at various spans under four-point bending. The effects of shear span-to-depth (a/d) ratio and sectional geometry on the structural capacity, stiffness and failure mode are studied. The effectiveness of the mechanical interlocking system between double-H-plank and round-pile for a continuous assembly is evaluated. Results suggest that the a/d ratio plays an important role in determining failure modes and ultimate capacities of double-H-plank and round-pile specimens. Additionally, a low a/d ratio or a larger depth incurs premature local crushing rather than flexural or shear failure. The mechanical interlocking system used to connect components together was found to be reliable as it effectively transfers bending loads from the double-H-plank to adjacent connected components even when the connection rotation is greater than 12°. Finally, FE modelling showed a good agreement with the experimental failure modes and satisfactorily estimated the failure loads and structural stiffness.

      PubDate: 2018-04-15T09:22:00Z
       
  • Probabilistic bolt load distribution analysis of composite single-lap
           multi-bolt joints considering random bolt-hole clearances and tightening
           torques
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Fengrui Liu, Meijuan Shan, Libin Zhao, Jianyu Zhang
      This paper presents a stochastic bolt load distribution analysis method of composite single-lap multi-bolt joints by using an improved three-stage spring-based method and Monte Carlo simulation. In the proposed method, the random properties of tightening torque, bolt-hole clearance, lamina properties and geometric parameters were involved. The allowable manufacturing tolerance band of parameters and clearance fit were considered, and a combining distribution function consisting of binomial distribution and normal distribution function was adopted for modeling the random tightening torque relaxation. To validate the proposed method, a set of composite single-lap three-bolt joints were designed and tested to achieve the stochastic bolt load distribution of the joint. Good agreements between the numerical and experimental stochastic bolt load distribution validated the proposed method. Furthermore, the probabilistic bolt load distributions of the three-bolt joints in four tightening torque conditions, including finger-tight, wrench torque, standard tightening torque and relaxation tightening torque, were investigated. It is found that tightening torque conditions and bolt-hole clearances have significant influences on the variation of the bolt load distribution, while the effects of other random parameters on the variation of the bolt load distribution are slight.

      PubDate: 2018-04-15T09:22:00Z
       
  • Effect of polyamide-6,6 (PA 66) nonwoven veils on the mechanical
           performance of carbon fiber/epoxy composites
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Bertan Beylergil, Metin Tanoğlu, Engin Aktaş
      In this study, carbon fiber/epoxy (CF/EP) composites were interleaved with polyamide-6,6 (PA 66) nonwoven veils at two different areal weight densities (17 and 50 gsm) to improve their delamination resistance against Mode-I loading. Mode-I fracture toughness (DCB), tensile, open hole tensile (OHT), flexural, compression, short beam shear (ILSS) and Charpy-impact tests were performed on the reference and PA 66 interleaved composite specimens. The DCB test results showed that the initiation and propagation Mode-I fracture toughness values of the composites were significantly improved by 84 and 171% using PA 66-17 gsm veils respectively, as compared to reference laminates. The use of denser PA 66-50 gsm veils in the interlaminar region led to higher improvement in fracture toughness values (349% for initiation and 718% for propagation) due to the higher amount of veil fibers involved in fiber bridging toughening mechanism. The incorporation of PA 66-50 gsm nonwoven veils also increased the ILSS and Charpy impact strength of the composites by 25 and 15%, respectively. On the other hand, the PA 66 veils reduced in-plane mechanical properties of CF/EP composites due to lower carbon fiber volume fraction and increased thickness.

      PubDate: 2018-04-15T09:22:00Z
       
  • Crashworthiness design of novel hierarchical hexagonal columns
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Xiang Xu, Yong Zhang, Jin Wang, Feng Jiang, Chun H. Wang
      Self-similar hierarchical structures are widely observed in nature, and have been credited with superior mechanical properties. In this paper, a novel self-similar hierarchical hexagonal columns (HHC) is proposed to improve structural crashworthiness performance. The self-similar hierarchical hexagonal columns are constructed by iteratively adding sub-hexagons at the corners of primary hexagon. To investigate the crashworthiness of HHC, the nonlinear finite element model is first developed and validated against experimental data obtained from 1st order HHC. Numerical investigations of 1st and 2nd order hierarchical hexagonal columns with different hierarchical levels are performed to compare with 0th order HHC, the results show that 1st and 2nd order hierarchical hexagonal columns improve the energy absorption and crush force efficiency by governing the material distribution, especially, 2nd order HHC exhibits significant advantage for energy absorption. In addition, parametric designs of 2nd order HHC are carried out to explore crashworthiness effect on hierarchical size ratio, cell wall thickness and impact velocity. The significant effects on both specific energy absorption (SEA) and the peak crushing force (PCF) are observed. The findings of this study offer a new route of designing novel crashworthiness structure with highly energy absorption capacity.

      PubDate: 2018-04-15T09:22:00Z
       
  • Vibration analysis of functionally graded carbon nanotube reinforced
           composites (FG-CNTRC) circular, annular and sector plates
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Rui Zhong, Qingshan Wang, Jinyuan Tang, Cijun Shuai, Bin Qin
      The intent of this paper is to firstly perform the vibration analysis of the functionally graded carbon nanotube reinforced composites (FG-CNTRC) circular, annular and sector plates with arbitrary boundary conditions by means of the semi-analytical method which is proposed by the author’s team. In the material model, the distribution of the carbon nanotubes is uniform or functionally graded along with the thickness direction of structures and four types of the CNTs distribution are studied in this paper. The refined rule of mixtures approach containing the efficiency parameters is adopted to determine the properties of the composite media. The admissible displacement functions of the FG-CNTRC circular, annular and sector plates are uniformly expanded as the modified Fourier series which embodies a standard cosine Fourier series and several auxiliary functions which are introduced to eliminate the limit of the boundary conditions. On this foundation, the first-order shear deformation elasticity theory is employed to construct the energy expression of the FG-CNTRC circular, annular and sector plates. Then the Ritz-variational energy method is used to decide the natural frequencies and the associated mode shapes. To examine the convergence, accuracy, stability and efficiency of the computational model, the comprehensive studies are conducted. Based on that, some crucial parametric studies covering the influence of the geometrical parameters, CNTs distributions, volume fraction of CNTs and boundary conditions are also investigated in detail.

      PubDate: 2018-04-15T09:22:00Z
       
  • Influence of low and high temperature on mixed adhesive joints under
           quasi-static and impact conditions
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): J.J.M. Machado, E.A.S. Marques, Lucas F.M. da Silva
      The increasing use of composite structures in the automotive industry is due to strict regulations regarding fuel efficiency and safety standards. The main advantage of the use of adhesives is the possibility of joining dissimilar materials, particularly composites. The technique studied was the mixed adhesive joints, as two or more adhesives can be used in a single lap joint combining the properties of those adhesives to attain mechanical performance superior to that obtained using those adhesives individually. The main goal was to assess if a previously validated combination of mixed adhesives in a composite joint, tested under quasi-static and impact conditions, offers the same advantage over the use of a single adhesive when subjected to low (−30 °C) and high (80 °C) temperatures. The influence of temperature on the behaviour of the composite joints was assessed in quasi-static and impact conditions allowing to infer the effect on each adhesive. Another important aspect of the use of this type of technique is to avoid the early delamination of the composite substrates. This method was found to improve the performance under quasi-static and impact conditions although its behaviour under the wide range of temperature tested was found to vary significantly.

      PubDate: 2018-04-15T09:22:00Z
       
  • Study of mechanical behavior of BNNT-reinforced aluminum composites using
           molecular dynamics simulations
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Ziyu Cong, Seungjun Lee
      Fabrication of metallic matrix boron nitride nanotubes (BNNT) composites have remained challenging due to their high reactivity of metals at elevated processing temperatures. Recently, however, the successful fabrication of BNNT-metal composites has been reported using a plasma technique. Since carbon nanotubes (CNT), which are a structural analogy of BNNTs, easily react with aluminum to form aluminum carbides at the interface, serving as mechanically weak points, BNNTs can be a good alternative for the reinforcing component of metal-matrix composites (MMC). In this study, we conducted several molecular dynamics (MD) simulations to investigate the mechanical behaviors of BNNT-Al composites under tensile loading. The simulations provided quantitative information on the mechanical properties of the BNNT composite, revealing the effect of various BNNT diameters and volume fractions. The contributions of the BNNT and Al component to the total improvement of mechanical properties were quantified through a component analysis. The analysis revealed that the effect of the volume fraction of BNNTs is more significant than that of the size. In addition, the quantified relation between the volume fraction of BNNTs and the enhancement in elasticity can be effectively used for the engineering design of BNNT-Al MMCs.

      PubDate: 2018-04-15T09:22:00Z
       
  • Crash responses under multiple impacts and residual properties of CFRP and
           aluminum tubes
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Qiang Liu, Hao Shen, Yinghan Wu, Zhencong Xia, Jianguang Fang, Qing Li
      This study aimed to explore the impact responses and residual properties of thin-walled carbon fiber reinforced plastics (CFRP) tubes and aluminum (Al) tubes subjected to multiple axial impacts. Five repeated impacts with the same impact energy were first conducted to evaluate the effect of repeated impact number, and then the crushing tests were performed to explore the post-impact residual behavior. Regardless of number of repeated impacts, the progressive end crushing modes for the CFRP tubes and stable progressive folding mode for aluminum tubes were identified under repeated dynamic impacts. The CFRP tubes exhibited the highest specific energy absorption (SEA) under the 1st impact, then the similar SEA values in the other four subsequent impacts; whereas the SEA of aluminum tubes fluctuated with the repeated impact numbers which were related to formation of different folds. The quasi-static crushing tests revealed that the residual SEAs of the CFRP tubes and aluminum tubes were not much influenced by the impact number, only within a difference of 5% under the 5 repetitive impacts conducted. It was demonstrated that the CFRP tubes had much better performance in energy absorption capability in comparison with the aluminum tubes in terms of repeated impacts and residual crushing tests.

      PubDate: 2018-04-15T09:22:00Z
       
  • Effect of internal surface damage on vibration behavior of a composite
           pipe conveying fluid
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Wasiu A. Oke, Yehia A. Khulief
      Composite pipes have become a viable alternative to metallic pipes in several applications. Flow-accelerated erosion and internal surface attack often result in thickness thinning that may compromise the structural integrity of the pipe and lead to its failure. In this paper, we investigate how the internal surface damage is reflected on the vibration behavior of a composite pipe conveying fluid. The defected pipe-fluid system is modeled using the extended Hamilton’s approach and discretized using the wavelet-based finite element method. The modal characteristics of the pipe vibrations have been obtained by solving the generalized eigenvalue problem. The developed model was validated and some benchmark solutions are presented to highlight the effects of the internal wall-thinning on the vibrational behavior of composite pipes conveying fluid. The obtained results facilitate the future research by revealing the potential of using the vibration signature as a basis for detection of erosion-induced internal defects in pipelines.

      PubDate: 2018-04-15T09:22:00Z
       
  • Design of filament-wound composite structures with arch-shaped cross
           sections considering fiber tension simulation
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Lei Zu, Hui Xu, Bing Zhang, Debao Li, Bin Zi
      The binding effect of fiber materials due to the winding tension during the filament winding process of arch-shaped cross sections was successfully evaluated using the Finite Element Method (FEM). The use of FEM was validated by comparing results obtained with the results from the numerical analysis of a classic cylindrical mandrel winding model. In this study, four methods were combined in the commercial finite element code ANSYS to predict the change trend of the residual stress of the layer and explore the relationship between the winding layer thickness and the winding relaxation effect. These methods include the element birth and death option, which was used to simulate the step-by-step winding process, the thermal parameter method, which produced the equivalent filament winding tension, contact analysis, which was used to carry out the transmission of radial pressure and deformation, and the restart method, which was used to simulate the procuring process. Compared with the mathematical algorithm and test of variable thickness, the results of FEM were in the range of allowable error. Therefore, these results provide a useful reference in designing the filament wound composite structures with considerably high fiber tensions.

      PubDate: 2018-04-15T09:22:00Z
       
  • Impacts of configurations on the strength of FRP anchors
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Wei Sun, Haifeng Liu, Yajun Wang, Tao He
      The usage of FRP anchors to prevent FRP strips from premature debonding failure is gaining acceptance in strengthening applications of concrete members. FRP anchors can fully develop the strength of FRP strips when they are properly designed. However, existing equations do not well include the comprehensive impact of the spike embedment depth, the bend ratio, the strength ratio of FRP anchor to FRP strip and the dowel angle on the anchor strength. Based on 64 tests failed in anchor rupture, this study proposes a comprehensive equation to determine the anchor strength. Comparisons between equation based predictions and 12 experimental results indicate the advantage of the proposed equation against existing equations. Then, the study propose a feasible technique, i.e. the bidirectional FRP patch, to improve the efficiency of current FRP anchors. Compared with equation based predictions for those FRP anchors without FRP patches, experimental results obtained from 20 specimens with FRP patches indicate significant increases on the anchor strength. This observation favors the usage of FRP patches to improve the efficiency of FRP anchors.

      PubDate: 2018-04-15T09:22:00Z
       
  • Vibration analysis for coupled composite laminated axis-symmetric
           doubly-curved revolution shell structures by unified Jacobi-Ritz method
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Kwangnam Choe, Qingshan Wang, Jinyuan Tang, Cijun shui
      In this paper, a unified Jacobi-Ritz method is presented and implemented to study the free vibration analysis of coupled composite laminated axis-symmetric doubly-curved revolution shell structures with general boundary conditions in the framework of the first-order shear deformation theory. The substructure of coupled structures mainly contains the laminated elliptical, hyperbolical, paraboloidal and cylindrical shells. In the theoretical analysis model, the multi-segment partitioning strategy is adopted. The displacement functions of each shell segment are uniformly expanded in the form of a double mixed series in which Jacobi polynomials are along the meridional direction and the standard Fourier series is along the circumferential direction, regardless of the shell components and the boundary conditions. The vibration results including frequency parameters and mode shapes of coupled composite laminated axis-symmetric doubly-curved revolution shell structures are easily obtained by means of the Ritz method. The major advantages of the present solutions for coupled structure are to eliminate the need of changing the displacement or the equations of motion and to improve the efficiency of modeling. The accuracy and reliability of the proposed method are verified with the FEM and literature results, and various numerical examples are presented for the free vibration of the various coupled structures of composite laminated axis-symmetric shell, and these results can be used as reference data.

      PubDate: 2018-04-15T09:22:00Z
       
  • Analysis of low velocity impacts on sandwich composite plates using cubic
           spline layerwise theory and semi empirical contact law
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): C.S. Rekatsinas, D.K. Siorikis, A.P. Christoforou, N.A. Chrysochoidis, D.A. Saravanos
      The theoretical and numerical framework for the simulation of impacts on thick sandwich composite plates is presented. It encompasses three new elements: 1) A three-dimensional layerwise theory, which approximates the in-plane and transverse displacements through the thickness using third-order Hermite spline polynomials that captures the high inhomogeneity of all interlaminar stresses present in the thick sandwich laminate. 2) The integration of the layerwise theory into a time domain plate spectral finite element with nodes collocated to Gauss-Lobatto-Legendre integration points, which provides a consistent semi-diagonal mass matrix and high-order spatial approximation in the plane of the structure, thus enabling high spatial convergence and fast explicit time integration of impact events. 3) A semi-empirical contact law that is derived from analytical expressions and validated with indentation experiments and numerical results, to provide the coupling between the impactor and target structure. Numerical simulations of the transient impact response obtained by the present method are correlated with 3D continuum finite element impact models and experimental results to quantify accuracy and computational speed. It is demonstrated, that the simulation of impacted sandwich composite plates requires integration of all three previous elements to obtain accurate and fast results.

      PubDate: 2018-04-15T09:22:00Z
       
  • Effective piezoelectric coefficients of cement-based 2–2 type
           piezoelectric composites based on a multiscale homogenization model
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Chuanqing Fu, Zhi Wang, Xianyu Jin, Xingyi Zhu, Jun Zhu
      The effective piezoelectric properties of the cement-based 2–2 type piezoelectric composites have been investigated both experimentally and theoretically. The two-scale asymptotic expansion method is employed to develop a homogenized model for the effective properties calculation. The validity of the theoretical solution is confirmed through the comparison with the experimental results. The influence of the volume fraction of the piezoelectric phase on the effective piezoelectric coefficients is then examined. It is found that higher volume fraction will induce obvious increment of the magnitude of the effective piezoelectric strain coefficients d 31 Eff , d 32 Eff , and d 33 Eff , however, the hydrostatic piezoelectric strain coefficient d h Eff will reach a maximum value at a lower volume fraction.

      PubDate: 2018-04-15T09:22:00Z
       
  • Manufacturing and compressive response of ultra-lightweight CFRP cores
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Pablo Vitale, Gaston Francucci, Helmut Rapp, Ariel Stocchi
      Three-dimensional carbon fiber reinforced polymer (CFRP) cores are high performance ultra-lightweight materials that can reduce the structural mass of vehicles used in the transportation and aerospace industry, increasing capabilities and performance, and reducing fuel consumption. In this work, three different carbon fiber cores are obtained using an interlocking method from flat composite laminates with different geometries. The density of the cores is maintained less than 48 kg m−3. Sandwich panels are manufactured using these cores and carbon fiber reinforced epoxy skins. Compressive properties of the sandwich panels are evaluated and the failure modes are studied. Experimental results are compared to those predicted by analytical modeling and finite element method analysis (FEM).

      PubDate: 2018-04-15T09:22:00Z
       
  • An experimental study on the radar absorbing characteristics of folded
           core structures
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Zhijin Wang, Chen Zhou, Valentin Khaliulin, Alexey Shabalov
      Folded core sandwich structures are promising multifunctional structures for both load bearing and radar absorbing capability. This paper presents an experimental study on the radar absorbing characteristics of folded core structures. The influences of various factors on the folded core radar cross section (RCS) are investigated. The experiments were carried out in an anechoic chamber. Comparisons are made between folded core samples and an aluminium flat panel. The results show that the folded core height has significant effects on the radar absorbing performance of V-pattern folded core, while core material only leads to a slight difference. The RCS of V-pattern folded core is lower than that of the flat panel, while the RCS of M-pattern folded core is of the same order of magnitude as that of the flat panel with a much wider range.

      PubDate: 2018-04-15T09:22:00Z
       
  • Experimental investigation of the quasi-static axial crushing behavior of
           filament-wound CFRP and aluminum/CFRP hybrid tubes
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Guangyong Sun, Zhen Wang, Jiaying Hong, Kai Song, Qing Li
      This study aims to investigate the effects of winding angles (25°, 50°, 75°, 90°; the 0° winding angle is along the axial direction of the tube) and thicknesses (3-ply, 6-ply, 9-ply) on crashworthiness characteristics of carbon fiber reinforced plastics (CFRP) tube and aluminum/CFRP hybrid tube molded by the filament winding technique through quasi-static crushing tests. The interaction between the outer CFRP tube and inner aluminum tube in a hybrid configuration was explored by comparing the sum of energy absorption of individual components with the hybrid form. It was found that both winding angle and wall thickness had significant influence on failure modes and crushing characteristics of both CFRP and hybrid tubes. With the same laminate thickness, increasing the winding angle decreased the specific energy absorption (SEA), energy absorption (EA) and peak crushing force (PCF) of pure CFRP and hybrid tubes. With the same winding angle of CFRP tube, increasing the thickness of CFRP tube increased the SEA, EA and PCF of both the CFRP and hybrid tubes. The SEA of 9-ply CFRP tube with winding angle of 25° and 9-ply CFRP/aluminum hybrid tube with winding angle of 25° were the highest of all the CFRP and hybrid tubes (48.74 J/g and 79.05 J/g), respectively. Moreover, EA of the hybrid tube exceeded the sum of that of the individual components thanks to the positive interaction between these components; making the hybrid tubes better crashworthiness than individual components.

      PubDate: 2018-04-15T09:22:00Z
       
  • Influence of stochastic variations in manufacturing defects on the
           mechanical performance of textile composites
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Xiao-Yi Zhou, P.D. Gosling
      This paper presents a methodology to evaluate the effects of microscopic manufacturing defects, namely fibre misalignment, waviness and volume fraction, on the mechanical performance. Influences of these defects on the effective elastic properties of composites are quantified by a dual homogenization method. For estimating stochastic characteristics of the properties induced by the variations in these defects, a probabilistic extension of the dual homogenization method is developed and numerically implemented through a perturbation-based stochastic finite element method. It is further incorporated in a multiscale finite element based reliability method to measure the influences of these manufacturing defects on structural performance in terms of reliability. The effectiveness of the proposed method in capturing defects is illustrated initially by investigating the effective elastic properties of a unidirectional fibre composite based yarn and then a plain woven textile composite. The capability of the proposed method in quantifying the variations in these defects is further demonstrated through statistical analysis of the effective elastic properties and a woven textile composite and structural reliability analysis of a textile composite laminate. This paper represents a significant advancement in the probabilistic prediction of the behaviour of woven and non-woven composites.

      PubDate: 2018-04-15T09:22:00Z
       
  • Effects of surface laser treatment on direct co-bonding strength of CFRP
           laminates
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): C. Leone, S. Genna
      Laser surface treatment is a promising technique to increase the adhesive strength of carbon fibres reinforced plastics joints. In this technique, the laser beam is adopted to remove the outer matrix layer up to the expose the underlying reinforcement. This study deals on the effect of laser treatment on the joint strength of CFRP laminate obtained by direct co-bonding. To this aim, laser treatments at different process conditions were performed on autoclave cured CFRP, adopting a pulsed Yb:YAG fiber laser. The obtained surfaces were characterized by microscopy. Single lap joints were obtained by infusion techniques by superposition of fresh laminates and laser treated laminates without any kind of adhesive. Untreated and sandpaper treated samples were adopted as reference specimens. After joints consolidation, mechanical tests were carried out; apparent shear strength was measured and post mortem analysis was performed. The results show that laser treatments allow the doubling of the apparent shear strength.
      Graphical abstract image

      PubDate: 2018-04-15T09:22:00Z
       
  • Behavior of steel fiber-reinforced concrete-filled FRP tube columns:
           Experimental results and a finite element model
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Aliakbar Gholampour, Togay Ozbakkaloglu
      This paper presents the results of an experimental study together with the first finite element (FE) model for the compressive behavior of fiber-reinforced polymer (FRP)-confined steel fiber-reinforced concrete (SFRC). 73 existing experimental test results of FRP-confined and actively confined SFRC specimens tested under axial compression were initially assembled. Additional axial compression tests were conducted on 16 actively confined SFRC specimens to address the gaps in the existing test database to compile a reliable database for the FE modeling of FRP-confined SFRCs. The analysis of experimental test results revealed that the compressive behavior of FRP-confined SFRCs is influenced by the steel fiber volume fraction and aspect ratio. New expressions were developed for the hoop rupture strain of the FRP jacket, axial strain-lateral strain relationship of FRP-confined and actively confined SFRC, and relationship between the confining pressure and the compressive strength of actively confined SFRC by considering the influences of the volume fraction and aspect ratio of internal steel fibers. A recently developed concrete damage-plasticity model, which was shown to be the most accurate currently available model for confined plain concrete, was adopted for the prediction of the compressive behavior of FRP-confined SFRC. The failure surface and flow rule of the model were modified based on the results from actively and FRP-confined SFRC. The results show that model predictions of the axial stress-axial strain, lateral strain-axial strain, axial stress-volumetric strain, plastic volumetric strain-axial plastic strain, and plastic dilation angle-axial plastic strain relationships are in good agreement with the experimental results of FRP-confined SFRC. The new model provides improved accuracy over the best performing existing models of FRP-confined plain concrete in predicting the behavior of FRP-confined SFRC.

      PubDate: 2018-04-15T09:22:00Z
       
  • Flexural performance of a hybrid GFRP-concrete bridge deck with composite
           T-shaped perforated rib connectors
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Yize Zuo, Ayman Mosallam, Haohui Xin, Yuqing Liu, Jun He
      In this study, the flexural performance of an innovative hybrid GFRP-concrete deck is evaluated. The proposed hybrid composite deck consists of a pultruded GFRP plate with T-shaped perforated ribs for resisting tensile stresses, while concrete with reinforcements is placed at the compressive side of the deck. In order to better understand the flexural performance of proposed hybrid decks under sagging moment, a total of six full-scale hybrid deck models were experimentally investigated. Five test parameters were considered, namely: (i) hole spacing, (ii) presence of bent-up rebars, (iii) quality of GFRP composites surface treatment, (iv) deck depth, and (v) type of reinforcements. Experimental results identified three different typical failure modes, namely: diagonal and longitudinal shear, as well as flexure. Furthermore, it was found that the inclusion of bent-up rebars, sand bonded to GFRP plates surfaces, and increasing deck thickness enhance the ultimate strength of the proposed hybrid deck. It was also concluded that the hole spacing and the reinforcement type have negligible influence on ultimate capacity of the proposed deck. Moreover, finite element models considering the laminate damage based on Hashin’s theory were built and load transfer and failure mechanisms of GFRP perforated ribs were discussed. The validity of the proposed analytical method, with respect to failure mode and ultimate strength for the hybrid deck, was confirmed through the close correlation between analytical and experimental results.

      PubDate: 2018-04-15T09:22:00Z
       
  • Static and fatigue analysis of bolted/bonded joints modified with CNTs in
           CFRP composites under hot, cold and room temperatures
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): U.A. Khashaba
      The present study evaluated for the first time, the tensile and fatigue properties of bolted/bonded scarf adhesive joints (SAJs) in carbon fiber reinforced polymer (CFRP) composites at room temperature of +25 °C, +50 °C and −70 °C. The adhesive layer of the SAJs was modified with multi-walled carbon nanotubes (CNTs) and the results are compared with respect to neat adhesive and adhesive thickness. A new simple approach was developed to measure bolt-hole elongation, which successfully differentiates between bearing failure and interfacial shear failure modes and loads. Results from tensile tests showed that the bolted/bonded SAJs can perform well at −70 °C with maximum loss in strength of 9.6% and stiffness improvement of 30%. Incorporation of CNTs into the adhesive layer improved fatigue lives, at +25 °C, by about 72.1%–97.8% compared with that of neat-adhesives. Interfacial shear failure, cohesive failure and CNTs pull-out are the dominated failure modes in the SAJs, whereas bearing, shear-out, longitudinal splitting and bolt fracture are observed for the bolted joints. Considerable attention was given to analyze the scatter in the tensile strength and fatigue life results.

      PubDate: 2018-04-15T09:22:00Z
       
  • Multiscale microstructural characterization of particulate-reinforced
           composite with non-destructive X-ray micro- and nanotomography
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): J. Nafar Dastgerdi, A. Miettinen, J. Parkkonen, H. Remes
      Methods based on X-ray tomography are developed to study the relevant statistical quantities describing the microstructural inhomogeneity of particulate reinforced composites. The developed methods are applied in estimating microstructural inhomogeneity parameters of composites containing metallic glass particles in metal matrix, extruded in varying pressure loads. This study indicates that the critical characteristics with regard to the effect of particle clustering are cluster size and shape, local volume fraction of particles in the cluster and the distance between clusters. The results demonstrate that the spatial distribution of reinforcement is very uneven and the amount of particle clustering varies with amount of reinforcement. Moreover, X-ray nanotomography was used to investigate the structure of individual clusters and the results suggest that high extrusion load may cause break-up of individual particle clusters so that their shape changes from solid and spherical to broken and ellipsoidal.

      PubDate: 2018-04-15T09:22:00Z
       
  • Multiscale modeling of polymer systems comprising nanotube-like inclusions
           by considering interfacial debonding under plastic deformations
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): S.M.R. Paran, G. Naderi, M.H.R. Ghoreishy, C. Dubois
      The mechanical properties of polymer nanocomposites are severely governed by the situation of the interphase region. Yet, a few was known about interfacial adhesion/debonding in the vicinity of polymer-nanofiller interface. The inadequateness of our information on such region takes its origin in the assumptions involved in theoretical models describing interfacial debonding. Particularly, zero interphase region, constant modulus, and elastic deformation assumptions make predictions unreliable when experimental mechanical characteristics are meticulously analyzed. In this work, multiscale modeling approach was implemented in prediction of plastic deformation of stress-strain of a typical thermoplastic polymer filled with nanotube-like inclusions. In contrast to the above-mentioned assumptions that take a naïve look at the interphase region, a finite element code was developed here to assist in interfacial debonding evaluation by considering a variable modulus for non-zero layer between polymer and nanotube-like filler phases under plastic deformation. Experimental plots of stress-strain on typical nanocomposites prepared varying the amount and surface chemistry of the nanofiller were used for approval of the model outcome. The use of finite element method in such a complex systems improved significantly the predictability of theories by making possible monitoring the effect of thickness of interphase on debonding behavior.

      PubDate: 2018-04-15T09:22:00Z
       
  • Numerical analysis and experimental observation of ultrasonic wave
           propagation in CFRP with curved fibers
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Takeshi Ashizawa, Yoshihiro Mizutani, Nobuyuki Toyama, Akira Todoroki, Yoshiro Suzuki
      The relationship between the propagation directions of ultrasonic wave and the direction of the principal axis of anisotropy in uni-directional CFRP with straight fiber is well known. However, the behavior of ultrasonic wave in CFRP with curved fibers is not clarified in details. In this paper, numerical analyses using the finite difference method were conducted to visualize the behavior of ultrasonic waves in CFRP with concentrically curved fibers. Numerical simulation results showed the energy of quasi-longitudinal ultrasonic wave curved along the fiber direction. In order to confirm the analytical result, CFRP specimen with curved fibers were prepared by utilizing 3D-printer and the behavior of ultrasonic propagation was observed by using Laser ultrasonic system. The observed results confirmed the analytical results that the ultrasonic wave curved along carbon fibers.

      PubDate: 2018-04-15T09:22:00Z
       
  • Aeroelasticity of composite plates with curvilinear fibres in supersonic
           flow
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Hamed Akhavan, Pedro Ribeiro
      The target of this investigation is to understand the aeroelastic (dynamic or static) instability of variable stiffness composite laminates (VSCLs) in the presence of supersonic airflow. The studied VSCLs have curvilinear fibre paths. Two different types of VSCLs are considered: the first type (already adopted in several previous researches) includes fibre path angles changing linearly from T 1 at right and left edges to T 0 at the centre, and the second type (not introduced before) includes fibre paths where their angles change linearly from T 0 at the left edge to T 1 at the right edge. Displacements and rotations in the plate are modelled by a Third-order Shear Deformation Theory (TSDT) and are discretised by a p-version finite element model. Aerodynamic forces due to supersonic airflow, in the steady or unsteady regime, are modelled using linear Piston theory and the equations of motion of the self-excited vibration system are formed using the principle of virtual work. Dynamic (flutter) and static (divergence) instabilities are identified using the eigenvalues of the linear system. Effects of different boundary conditions and various fibre angles as well as the influence of airflow direction on the flutter and divergence occurrence in VSCL plates are studied.

      PubDate: 2018-04-15T09:22:00Z
       
  • A metamodel-based optimization approach to reduce the weight of composite
           laminated wind turbine blades
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Alejandro Albanesi, Nadia Roman, Facundo Bre, Victor Fachinotti
      In wind turbine blades, the complex resultant geometry due to the aerodynamic design cannot be modified in the successive mechanical design stage. Hence, the reduction of the weight and manufacturing costs of the blades while assuring appropriate levels of structural stiffness, integrity and reliability, require a composite material layout that must be optimally defined. The aim of this work is to present a metamodel-based method to optimize the composite laminate of wind turbine blades. This methodology combines a genetic algorithm (GA) with an artificial neural network (ANN) in order to reduce the computational cost of the optimization procedure. Therefore, at first, representative samples were built to train and validate the ANN model, and then, the ANN model is coupled with GA to find the optimal structural blade design. As an actual case study, the method was applied to redesign a medium-power 40-kW wind turbine blade to reduce its mass while structural and manufacturing constrained are fulfilled. The results indicated that is possible to save of up to 20% of laminated mass compared to a reference design. Furthermore, a 40% reduction of the computational cost was achieved in contrast with the typical simulation-based optimization approach.

      PubDate: 2018-04-15T09:22:00Z
       
  • Buckling of a piezoelectric nanobeam with interfacial imperfection and van
           der Waals force: Is nonlocal effect really always dominant'
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Yong-Dong Li, Ronghao Bao, Weiqiu Chen
      With the development of NEMSs (nano-electro-mechanical systems), the size-dependent behavior has been an active topic. The scale parameter seems an essential factor dominating mechanical behavior at nanoscale. However, is it always dominant' This is a question deserving careful investigation. For this reason, the buckling of a bi-layered PE (piezoelectric) nanobeam is analyzed. The main purpose is to reveal and compare the effects of the nonlocal scale, imperfect interface, interlaminar van der Waals force and loading ratio. The imperfect interface is modeled by normal and shear springs, and the van der Waals force is represented by the Hamaker formula. Based on the principle of virtual work, the analytical solution of the critical buckling loading is derived by using the trigonometric shear deformation theory. After the verification in some degenerated cases, parametric studies are conducted. It is indicated that if the nonlocal parameter varies in the typical range [0, 4 nm^2], it only has quite limited effect on the buckling behavior, as compared with the other three factors. In this case, although the buckling relies on the nonlocal scale, it is far more dependent on the conventional non-nanoscale factors. The conclusions can provide references for optimal design of NEMSs.

      PubDate: 2018-04-15T09:22:00Z
       
  • Time-dependent assessment and deflection prediction of prestressed
           concrete beams with unbonded CFRP tendons
    • Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Tiejiong Lou, Theodore L. Karavasilis
      This paper presents the assessment of the time-dependent behavior and the prediction of the long-term deflection of concrete beams prestressed with internal unbonded carbon fiber reinforced polymer (CFRP) tendons. A numerical model for the time-dependent analysis of concrete beams prestressed with unbonded tendons is calibrated against experimental results. Parametric numerical simulations are then conducted on simply supported unbonded prestressed concrete beams subjected to long-term sustained loads to investigate the effect of using CFRP tendons instead of low-relaxation steel ones, the magnitude of the initial prestress, the loading conditions, and the quantity of the compressive reinforcing steel. The results show that the long-term prestress loss of beams with CFRP tendons is considerably higher than that of beams with steel tendons. Moreover, it is shown that increasing the quantity of compressive reinforcing steel leads to a substantial decrease in long-term downward deflection. A modification of the ACI 318-14 equation is proposed to predict the time-dependent deflection of prestressed concrete beams with unbonded FRP or steel tendons.

      PubDate: 2018-04-15T09:22:00Z
       
  • A simplified method to predict the fire resistance of RC beams
           strengthened with near-surface mounted CFRP
    • Abstract: Publication date: 1 June 2018
      Source:Composite Structures, Volume 193
      Author(s): Jiangtao Yu, Keke Liu, Ling-zhi Li, Yichao Wang, Kequan Yu, Qingfeng Xu
      A simplified method was proposed to predict the fire resistance of flexure-dominated reinforced concrete (RC) beams strengthened with near-surface mounted (NSM) carbon fiber reinforced polymer (CFRP). Based on the results of previous experimental observations and theoretical analyses, “steel yielding after FRP slipping” and “FRP fracture after steel yielding” were presumed to be the possible failure modes for NSM-FRP strengthening system under fire. An algorithm was thus developed to evaluate the fire resistance of the strengthening system. A series of pull-out tests were carried out to obtain the bond-slip relationships of NSM-FRP at different elevated temperatures for the proposed algorithm. Then this method was used to predict the fire resistance of nine RC beams strengthened with NSM-FRP, which were subjected to a sustained load and the ISO834 standard fire. The predictions showed good agreement with the test results, indicating the effectiveness of the proposed method. This study provides a helpful reference for the fire resistance design of flexure-dominated RC beans strengthened with NSM-FRP in engineering practice.

      PubDate: 2018-04-15T09:22:00Z
       
  • Elastic properties of 3D printed fibre-reinforced structures
    • Abstract: Publication date: 1 June 2018
      Source:Composite Structures, Volume 193
      Author(s): Haider Al Abadi, Huu-Tai Thai, Vidal Paton-Cole, V.I. Patel
      This paper aims to evaluate the elastic properties of fibre-reinforced polymer (FRP) structures printed by three-dimensional (3D) printing technology. Both experimental and theoretical approaches are adopted to investigate the performance of FRP 3D-printed structures and predict their elastic properties. Three types of FRP materials were considered in this study including Carbon, Kevlar and Glass printed in selected arrangements of fibre filaments and Nylon matrix. An analytical model was developed based on the Volume Average Stiffness (VAS) method to predict elastic properties of 3D printed coupons, while the numerical model was developed using Abaqus to predict the failure modes and damage in the FRP 3D-printed coupons tested in this study. A parametric study was carried out to develop the mathematical expressions for calculating elastic properties of FRP 3D-printed structures. The parametric study indicates that the level of fibre reinforcements and their orientation arrangement have significant effects on the structural performance of FRP 3D-printed composite sections.

      PubDate: 2018-04-15T09:22:00Z
       
  • Fracture analysis of a metal to CFRP hybrid with thermoplastic interlayers
           for interfacial stress relaxation using in situ thermography
    • Abstract: Publication date: 1 June 2018
      Source:Composite Structures, Volume 193
      Author(s): Jannik Summa, Michael Becker, Felix Grossmann, Markus Pohl, Markus Stommel, Hans-Georg Herrmann
      In this work a plane hybrid-structure composed of a metal and a carbon-fiber-reinforced-polymer (CFRP) constituent is introduced. Hereby an interlayer is inserted between the metal and the CFRP constituent, pursuing the task of stress relaxation. In order to study the effect of interfacial stress relaxation several thermoplastics are investigated. In situ passive thermography is used to assess the damage during quasi-static and fatigue mechanical loading. Thus, mechanical properties are correlated with corresponding damage-quantities from non-destructive testing (ndt). These results reveal that transversal cracking and mode-I delamination are the dominant failure processes, which strongly depend on the thermoplastic material. Additional finite element analysis describes strain-energy- and stressconcentrations, which coincide with the observed damage mechanisms and the origins of fracture.

      PubDate: 2018-04-15T09:22:00Z
       
  • Process induced shape distortions of self-reinforced poly(ethylene
           terephthalate) composites
    • Abstract: Publication date: 1 June 2018
      Source:Composite Structures, Volume 193
      Author(s): L. Jerpdal, M. Åkermo, D. Ståhlberg, A. Herzig
      This paper investigates shape distortion and tensile properties of hot consolidated Self-reinforced poly(ethylene terephthalate) (SrPET) by evaluating the influence from stretching before consolidation and annealing after consolidation. Spring-in angle and warpage is measured from V-shaped samples that are hot consolidated from a woven fabric that is stretched to different degrees during forming. Following the same process conditions, tensile stiffness is measured from plane laminates. This study confirms that stretching the SrPET-material during forming enhances the tensile modulus but introduces shape distortions with negative spring-in and increases warpage. However also non-stretched SrPET components experience spring-back in the same level as glass- or carbon reinforced PET composite, which is unexpected. The tensile modulus is reduced and spring-in angle further influenced when the SrPET-samples are exposed to higher temperature after consolidation. This study shows how easily the characteristics of a component made from SrPET-material are influenced by stresses developed during material forming and further by release of these stresses when exposed to higher temperatures as in post processes or even in the use phase of the component.

      PubDate: 2018-04-15T09:22:00Z
       
  • Extended formulations of evolutive laws and constitutive relations in
           non-smooth plasticity and viscoplasticity
    • Abstract: Publication date: 1 June 2018
      Source:Composite Structures, Volume 193
      Author(s): Fabio De Angelis
      Plastic and viscoplastic constitutive behavior is of interest in the mechanical modeling of many composite materials and structures. In this paper evolutive laws and constitutive relations in non-smooth plasticity and viscoplasticity are presented by means of a formulation which takes advantage of the proper concepts required to deal with non-smooth problems in plasticity and viscoplasticity. This adopted framework is endowed with considerable advantages in comparison with other formulations of non-smooth problems. In fact, subdifferential calculus shows to be the proper tool to deal with non-smooth functions and corners in plasticity and viscoplasticity. Plastic and viscoplastic constitutive models are revisited and expressed in subdifferential form by adopting the more general context presented herein that includes Koiter’s theory as a special case. The evolutive equations in plasticity and viscoplasticity are derived as optimality conditions of a suitably defined Lagrangian in a form usually not considered. Consequently, alternative equivalent expressions of the evolution laws and of the loading/unloading conditions are presented and the equivalence among them is described. Furthermore, the present approach shows to be useful for extensions into other types of elastoplastic materials and for clarifications on the relations existing between different constitutive models in non-smooth viscoplasticity.

      PubDate: 2018-04-15T09:22:00Z
       
  • Free vibration of thin functionally graded viscoelastic open-cell foam
           plates on orthotropic visco-Pasternak medium
    • Abstract: Publication date: 1 June 2018
      Source:Composite Structures, Volume 193
      Author(s): H.A. Zamani, M.M. Aghdam, M. Sadighi
      The present study deals with vibration of functionally graded viscoelastic open-cell foam plates resting on three parameters orthotropic visco-Pasternak foundation. The kinematic and constitutive relations are described by classical plate theory and separable kernels framework, respectively. Viscoelastic treatment of bulk and shear moduli of plates are modeled by standard solid and Kelvin-Voigt models. Also, nonlinear non-symmetric porosity distribution through thickness is obtained using power law and neutral surface decoupling. The integro-PDE of motion with frequency-dependent coefficients is figured out by weighted residual method and iterative numerical algorithm to obtain natural frequencies and modal loss factors. In elastic domain, frequencies are compared with those reported for thin functionally graded plates resting on isotropic Pasternak foundation while in the viscoelastic domain, complex frequencies are compared for standard solid and Kelvin-Voigt viscoelastic plates where acceptable correlation is observed. Influences of various boundary conditions including fully clamped and fully free edge conditions, aspect ratio, coefficients and orthotropy angle of medium on dynamic characteristics are scrutinized via a comprehensive parametric study which could be used as benchmark results in future studies.

      PubDate: 2018-04-15T09:22:00Z
       
  • High-power laser resistance of filled sandwich panel with truss core: An
           experimental study
    • Abstract: Publication date: 1 June 2018
      Source:Composite Structures, Volume 193
      Author(s): Wu Yuan, Jiangtao Wang, Hongwei Song, Te Ma, Wenjun Wu, Junning Li, Chenguang Huang
      We reported a new function of sandwich panels with truss cores, i.e., superior performance under intense local heat flux induced by continuous wave laser. To further enhance the laser resistance, lightweight ablative material and thermal insulation material are filled in the sandwich panel respectively. A dimensional analysis is developed to find core filler materials with appropriate properties. Experiments show that sandwich panels filled with the compound of silicone resin and carbon powder, a typical ablative material, and porous ceramic, a typical thermal insulation material significantly improve the local heat flux resistance compared with monolithic plates and unfilled sandwich panels. The full-field temperature history and dynamic damage evolution of the back surface are recorded and compared, and the failure time to reach the melting point is prolonged in the following order: monolithic plate, unfilled sandwich panel, sandwich panel filled with ceramic, sandwich panel filled with the compound of silicone resin and carbon powder. Considering the lightweight design requirement of such structures, resistance in relation to specific weight is also evaluated and discussed.

      PubDate: 2018-04-15T09:22:00Z
       
  • Parameter optimization to avoid propeller-induced structural resonance of
           quadrotor type Unmanned Aerial Vehicle
    • Abstract: Publication date: 1 June 2018
      Source:Composite Structures, Volume 193
      Author(s): Abera Tullu, Youngseop Byun, Jae-Nam Kim, Beom-Soo Kang
      Structural resonance in Unmanned Aerial Vehicle (UAV) is one of the major challenges that impose malfunctioning of the UAV sensor thereby degrading maneuverability. Vibration in quadrotor UAV is induced, mainly, due to the rotation of its motor-driven propellers. The constructive interference between the excitation frequencies of the propellers and fundamental frequencies of the UAV structure causes structural resonance. To avoid this structural resonance, the lowest fundamental frequency of the whole UAV structure has to be higher than the maximum working excitation frequencies of the propellers. The fundamental frequency of the quadrotor UAV structure depends on the parameters such as dimensions and stiffness of motor-supporting arms and landing gears as well as the mount location of the landing gears on the arms. The surrogate model that approximates functional dependency of the first fundamental frequency of the quadrotor UAV structure on the mentioned parameters is developed. Using the developed model and a non-linear sequential quadratic programming algorithm, the optimal values of the parameters at which the first fundamental frequency of the structure can be maximized are obtained. The adequacy of the developed surrogate model to approximate the functional form of the first fundamental frequency is verified through various statistical and experimental methods.

      PubDate: 2018-04-15T09:22:00Z
       
  • Micromechanical and dynamic mechanical analyses for characterizing
           improved interfacial strength of maleic anhydride compatibilized basalt
           fiber/polypropylene composites
    • Abstract: Publication date: 1 June 2018
      Source:Composite Structures, Volume 193
      Author(s): Seongyeol Pak, Sunmin Park, Young Seok Song, Doojin Lee
      For fiber reinforced polymer composites, it is important to obtain a good interfacial bonding between the fibers and the polymer matrix to enhance the physical properties of the composites. In particular, the mechanical and thermal properties of the composites differ depending on the interfacial bonding strength, lengths, and orientations of the fibers. We investigate the microstructural anisotropy of the basalt fiber reinforced polypropylene composites and evaluate their mechanical properties, such as elastic modulus and ultimate tensile strength in order to understand the relationship between the local anisotropy and the mechanical strength of the composites. Dynamic mechanical and thermal analyses are performed to characterize the grafting effect of maleic anhydride polypropylene on the basalt fibers. The grafting effect enhances the bonding strength between the basalt fibers and matrix and the thermomechanical properties of the composites. The elastic modulus and ultimate tensile strength of the composites with the grafting effect show enhancement compared to the composites without the grafting effect. The predictions of the elastic modulus by the Mori–Tanaka model and the ultimate tensile strength by the rule of mixture model are in good agreement with the experimental results.

      PubDate: 2018-04-15T09:22:00Z
       
  • Bond-slip effect in flexural behavior of GFRP RC slabs
    • Abstract: Publication date: 1 June 2018
      Source:Composite Structures, Volume 193
      Author(s): Omid Gooranorimi, Guillermo Claure, Wimal Suaris, Antonio Nanni
      The use of glass fiber reinforced polymer (GFRP) composite bars as internal reinforcement for concrete is rapidly increasing especially in structures exposed to aggressive environments. A proper bond mechanism between GFRP bar and concrete is essential to ensure proper functioning of such structures. The slippage between the concrete and reinforcement has usually been ignored in numerical modeling of reinforced concrete (RC) structures. In this study, the effect of the bond action in flexural behavior of GFRP RC slabs was investigated. The analysis was first performed by considering a perfect bond between the concrete and reinforcement and ignoring any slippage. Next, an experimentally obtained bond-slip relation was used to replace the unrealistic perfect bond assumption. The predicted flexural load-deflection response of the slab was compared to the experimental data. The result obtained by incorporating the bond-slip model showed a better agreement with the experimental data. Hence, considering the slippage between the GFRP and concrete may be necessary when accurate deflection estimate is required under the service condition. Additionally, it was shown that the perfect bond assumption was sufficiently safe for the design of the GFRP RC slabs.

      PubDate: 2018-04-15T09:22:00Z
       
  • Coupled effect of CNT waviness and agglomeration: A case study of
           vibrational analysis of CNT/polymer skew plates
    • Abstract: Publication date: 1 June 2018
      Source:Composite Structures, Volume 193
      Author(s): Enrique García-Macías, Rafael Castro-Triguero
      The main contribution of this work lies in a critical comparison of different mean-field homogenization approaches for the study of carbon nanotube-reinforced polymers with waviness and agglomeration effects. In particular, this paper focuses on the consistency of predictions in terms of diagonal symmetry of the constitutive tensors and comparison against theoretical bounds. The analysis comprises general axisymmetric orientation distributions of fillers, both planar sinusoidal and helical wavy fillers, as well as different agglomeration schemes by means of a two-parameter agglomeration model. The results demonstrate that waviness and agglomeration simultaneously weaken the macroscopic stiffness of composites. The results also reveal that the widely used Mori-Tanaka method fails to simulate the coupled effect of these two phenomena and, therefore, it is necessary to apply extended approaches with consideration of ad hoc Eshelby’s tensors that account for particular wavy microstructures. A case study of carbon nanotube-reinforced skew plates is finally presented to illustrate the coupled effect of waviness and agglomeration on the macroscopic vibrational behavior.

      PubDate: 2018-04-15T09:22:00Z
       
  • Estimation of a matrix-fiber interface cohesive material law in
           FRCM-concrete joints
    • Abstract: Publication date: 1 June 2018
      Source:Composite Structures, Volume 193
      Author(s): Tommaso D'Antino, Pierluigi Colombi, Christian Carloni, Lesley H. Sneed
      The application of composite materials to strengthen existing structural elements is a valid alternative to traditional strengthening techniques. Fiber reinforced cementitious matrix (FRCM) composites have been successfully employed to strengthen existing reinforced concrete (RC) and masonry structures in bending, shear, torsion, and to confine axially loaded elements. Although failure of FRCM strengthened elements depends on different parameters, such as the composite and substrate geometrical and mechanical properties, debonding at the matrix-fiber interface is generally the failure mechanism. Therefore, the study of the bond behavior of FRCM composites is a key topic to develop reliable design procedures. Numerous experimental campaigns were carried out recently to study the bond behavior of different FRCM composites. An analytical model is employed in this paper to describe the bond behavior of FRCM-concrete joints and different trilinear cohesive material laws are defined based on the experimental results. The experimental and corresponding analytical load response, strain profile, slip profile, and shear stress profile along the bonded length are compared. An analytical formulation of the bonded length needed to fully develop the stress-transfer mechanism at the matrix-fiber interface, i.e. the effective bond length, is provided for the trilinear cohesive material law employed.

      PubDate: 2018-04-15T09:22:00Z
       
  • Multi-functional aramid/epoxy composite for stealth space hypervelocity
           impact shielding system
    • Abstract: Publication date: 1 June 2018
      Source:Composite Structures, Volume 193
      Author(s): Young-Woo Nam, Sarath Kumar Sathish Kumar, Venkat Akhil Ankem, Chun-Gon Kim
      In this study, a stealth space hypervelocity impact shielding system containing electromagnetic wave absorption capability and impact shielding system was presented and verified from design to fabrication. To improve the microwave absorption performance of the proposed system, the electrical modification of aramid fabric via a RF magnetron silver-sputtering coating technique was used. The proposed thin stealth space shielding composite demonstrated excellent microwave absorption performance in the target frequency range from C-band to Ku-band (4–18 GHz) without using carbonaceous nano-conductive material in a polymer matrix (4.970-mm total thickness) while maintaining the thin total thickness. To check the impact shielding performance, hypervelocity impact experiments were conducted using two-stage light-gas gun projectile velocities between 2.7 and 3.2 km/s. The average specific energy absorbed of silver-coated aramid/epoxy composites was comparable to that of pristine (uncoated) material. The type and shape of failures in the pristine and silver-coated aramid/epoxy composites were similar. In addition, interlaminar shear-strength (ILSS) tests were performed to check the mechanical performance of the proposed shielding system according to ASTM D 2344. Based on these results, our proposed stealth space shielding system proved to be a promising candidate for military satellite systems.

      PubDate: 2018-04-15T09:22:00Z
       
  • Experimental and numerical analysis of the shear nonlinear behaviour of
           Nomex honeycomb core: Application to insert sizing
    • Abstract: Publication date: 1 June 2018
      Source:Composite Structures, Volume 193
      Author(s): Juan de Dios Rodriguez-Ramirez, Bruno Castanie, Christophe Bouvet
      This work is a contribution to the understanding of the nonlinear shear behaviour caused by cell postbuckling in Nomex honeycomb cores. First, an experimental benchmark study was made of different designs for the shear testing of honeycomb cores. Then, several test specimens were fabricated and tested, a 3D DIC system being used to measure and record the displacements. An Artificial Neural Network (ANN) was also used to identify the onset of bucking and collapse of the cells. The influence of the overall boundary conditions of shear tests on the buckling of the cells is presented both experimentally and numerically. The reversibility and test procedure results suggest that it may be possible to allow the shear strength to be increased by up to 35% under certain conditions.

      PubDate: 2018-04-15T09:22:00Z
       
  • Experimental and numerical characterization of thin woven composites used
           in printed circuit boards for high frequency applications
    • Abstract: Publication date: 1 June 2018
      Source:Composite Structures, Volume 193
      Author(s): Gautier Girard, Mohamad Jrad, Slim Bahi, Marion Martiny, Sébastien Mercier, Laurent Bodin, David Nevo, Sophie Dareys
      The elastic orthotropic behavior of thin woven composites is studied combining a numerical and experimental strategy. For thin materials, in-plane properties are measured by classical tensile tests and digital image correlation. The out-of-plane properties are derived performing finite element simulations at the level of the internal structure of the laminate. Indeed, the glass fiber arrangement in the yarn and the weaving pattern are defined based on microtomography and SEM observations. So a representative unit cell is found. A statistical approach is further proposed to derive the behavior of the warp and fill yarns, since the fiber position may fluctuate between yarns. For the considered laminate, the matrix (resin and ceramic inclusion) behavior is unknown and difficult to measure. Therefore an inverse method is proposed. By comparing with measured in-plane elastic moduli, behaviors of the matrix, of yarns and of the laminate are defined. The present homogenization strategy is exemplified by laminates used in printed circuit boards for high frequency applications. This approach has also been applied to investigate the evolution of the elastic moduli of the laminate with temperature. Those information, usually not available in the literature, are important when dealing with reliability of printed circuit boards during thermal cycles.
      Graphical abstract image

      PubDate: 2018-04-15T09:22:00Z
       
  • Flexural creep tests and long-term mechanical behavior of fiber-reinforced
           polymeric composite tubes
    • Abstract: Publication date: 1 June 2018
      Source:Composite Structures, Volume 193
      Author(s): Zengqin Yang, Hui Wang, Xiaofei Ma, Fulin Shang, Yu Ma, Zhenwei Shao, Demen Hou
      An experimental investigation of the long-term creep behavior of fiber reinforced polymeric composite tubes subjected to flexural loading was performed. The tubes were first tested under a three-point bending scheme at room temperature to determine the ultimate flexural strength (UFS) and to identify the characteristic failure mode and possible failure locations. Creep tests were then carried out at stress levels of 45%, 55%, 65%, and 75% of the UFS at constant temperatures ranging from −60 °C to 100 °C for 500 h, and strain measurements over time were recorded. The tubes were further tested at varying temperatures by applying 22.5 thermal cycles between −60 °C and 100 °C and 9.5 thermal cycles between −160 °C and 80 °C. Similar flexural loads were applied simultaneously on the tubes. Long-term creep deformation of the tube was evaluated using the time-temperature-stress superposition principle, the derived creep main curves, and the Findley model. Finally, the creep deformation and mechanical strength of the tube at expected service conditions over its entire lifetime were predicted.

      PubDate: 2018-04-15T09:22:00Z
       
  • Three-dimensional FE2 method for the simulation of non-linear,
           rate-dependent response of composite structures
    • Abstract: Publication date: 1 June 2018
      Source:Composite Structures, Volume 193
      Author(s): E. Tikarrouchine, G. Chatzigeorgiou, F. Praud, B. Piotrowski, Y. Chemisky, F. Meraghni
      In this paper, a two scale Finite Element method (FE2), is presented to predict the non-linear macroscopic response of 3D composite structures with periodic microstructure that exhibit a time-dependent response. The sensitivity to the strain rate requires an homogenization scheme to bridge the scales between the macroscopic boundary conditions applied and the local evaluation of the strain rate. In the present work, the effective response of composite materials where the matrix has a local elasto-viscoplastic behavior with ductile damage are analyzed using periodic homogenization, solving simultaneously finite element problems at the microscopic scale (unit cell) and at the macroscopic scale. This approach can integrate any kind of periodic microstructure with any type of non-linear behavior for the constituents (without the consideration of non-linear geometric effects), allowing to treat complex mechanisms that can occur in every phase and at their interface. The numerical implementation of this simulation strategy has been performed with a parallel computational technique in ABAQUS/Standard,with the implementation of a set of dedicated scripts. The homogenization process is performed using a user-defined constitutive law that solve a set full-field non-linear simulations of a Unit Cell and perform the necessary homogenization of the mechanical quantities. The effectiveness of the method is demonstrated with three examples of 3D composite structures with plastic or viscoplastic and ductile damage matrix. In the first example, the numerical results obtained by this full field approach are compared with a semi-analytical solution on elastoplastic multilayer composite structure. The second example investigates the macroscopic response of a complex viscoplastic composite structure with ductile damage and is compared with the mean field Mori-Tanaka method. Finally, 3D corner structure consisting of periodically aligned short fibres composite is analysed under complex loading path. These numerical simulations illustrate the capabilities of the FE2 strategy under non-linear regime. when time dependent constitutive models describe the response of the constituents.

      PubDate: 2018-04-15T09:22:00Z
       
  • Vibration reduction in truss core sandwich plate with internal nonlinear
           energy sink
    • Abstract: Publication date: 1 June 2018
      Source:Composite Structures, Volume 193
      Author(s): Jianen Chen, Wei Zhang, Minghui Yao, Jun Liu, Min Sun
      The effects of an internal nonlinear energy sink (NES) on a truss core sandwich plate in dynamics are investigated. The energy dissipation of the NES is studied with the sandwich plate excited by a half-wave shock. It is found that exceptional vibration absorption is achieved by the NES. Moreover, the relative motion between the sandwich plate and the NES remains in the acceptable range of the hollow truss core until the shock amplitude becomes too large. The slow flow equation and the frequency response of the system are obtained by employing the complexification-averaging method. Although the NES exhibits excellent performance when the sandwich plate is under an excitation with a relatively small amplitude, the efficiency is gradually diminished with the emergence of a stable higher branch and the merging of higher and lower branches. During the entire process, the NES does not collide with the face sheet of the sandwich plate. Further, the variation of vibration absorption performance of the NES with the increase of strut radius is investigated. It is demonstrated that the variation of the strut radius has a greater influence on the vibration absorption with a harmonic load in comparison to absorption with a shock load.

      PubDate: 2018-04-15T09:22:00Z
       
  • Free vibration of anti-symmetric angle-ply layered circular cylindrical
           shells filled with quiescent fluid under first order shear deformation
           theory
    • Abstract: Publication date: 1 June 2018
      Source:Composite Structures, Volume 193
      Author(s): M.D. Nurul Izyan, Z.A. Aziz, K.K. Viswanathan
      Free vibration of layered circular cylindrical shell filled with fluid with an anti-symmetric angle-ply walls including first-order shear deformation theory is presented. The fluid is assumed to be quiescent and inviscid. The permeability condition on the fluid-shell interface is applied to ensure the contact between the fluid and shell wall. The governing equations are obtained in terms of displacement and rotational functions. These functions are assumed in a separable form, resulting into a system of ordinary differential equation. Bickley-type spline of order three is applied to the problem, along with the equations of boundary conditions, bringing out into the system of homogeneous equations and become as a generalized eigenvalue problem. This problem is solved for frequency parameter with an associated eigenvectors. The effect of shell geometry, types of material, ply-orientations, number of layers and boundary conditions on frequencies are studied.

      PubDate: 2018-04-15T09:22:00Z
       
 
 
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