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  Subjects -> ENGINEERING (Total: 2277 journals)
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ENGINEERING (1204 journals)                  1 2 3 4 5 6 7 | Last

Showing 1 - 200 of 1205 Journals sorted alphabetically
3 Biotech     Open Access   (Followers: 7)
3D Research     Hybrid Journal   (Followers: 19)
AAPG Bulletin     Hybrid Journal   (Followers: 6)
AASRI Procedia     Open Access   (Followers: 15)
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: 230)
Acta Geotechnica     Hybrid Journal   (Followers: 7)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Polytechnica : Journal of Advanced Engineering     Open Access   (Followers: 2)
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: 6)
Advanced Science     Open Access   (Followers: 5)
Advanced Science Focus     Free   (Followers: 3)
Advanced Science Letters     Full-text available via subscription   (Followers: 7)
Advanced Science, Engineering and Medicine     Partially Free   (Followers: 7)
Advanced Synthesis & Catalysis     Hybrid Journal   (Followers: 17)
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: 7)
Advances in Engineering Software     Hybrid Journal   (Followers: 25)
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: 10)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 21)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 25)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 9)
Advances in Natural Sciences: Nanoscience and Nanotechnology     Open Access   (Followers: 28)
Advances in Operations Research     Open Access   (Followers: 11)
Advances in OptoElectronics     Open Access   (Followers: 5)
Advances in Physics Theories and Applications     Open Access   (Followers: 12)
Advances in Polymer Science     Hybrid Journal   (Followers: 41)
Advances in Porous Media     Full-text available via subscription   (Followers: 4)
Advances in Remote Sensing     Open Access   (Followers: 37)
Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Aerobiologia     Hybrid Journal   (Followers: 1)
African Journal of Science, Technology, Innovation and Development     Hybrid Journal   (Followers: 4)
AIChE Journal     Hybrid Journal   (Followers: 30)
Ain Shams Engineering Journal     Open Access   (Followers: 5)
Akademik Platform Mühendislik ve Fen Bilimleri Dergisi     Open Access  
Alexandria Engineering Journal     Open Access   (Followers: 1)
AMB Express     Open Access   (Followers: 1)
American Journal of Applied Sciences     Open Access   (Followers: 28)
American Journal of Engineering and Applied Sciences     Open Access   (Followers: 11)
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)
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: 12)
Applied Clay Science     Hybrid Journal   (Followers: 5)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 12)
Applied Magnetic Resonance     Hybrid Journal   (Followers: 4)
Applied Nanoscience     Open Access   (Followers: 7)
Applied Network Science     Open Access  
Applied Numerical Mathematics     Hybrid Journal   (Followers: 5)
Applied Physics Research     Open Access   (Followers: 3)
Applied Sciences     Open Access   (Followers: 2)
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: 4)
Archives of Foundry Engineering     Open Access  
Archives of Thermodynamics     Open Access   (Followers: 7)
Arid Zone Journal of Engineering, Technology and Environment     Open Access   (Followers: 2)
Arkiv för Matematik     Hybrid Journal   (Followers: 1)
ASEE Prism     Full-text available via subscription   (Followers: 3)
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: 8)
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: 4)
Bautechnik     Hybrid Journal   (Followers: 1)
Bell Labs Technical Journal     Hybrid Journal   (Followers: 23)
Beni-Suef University Journal of Basic and Applied Sciences     Open Access   (Followers: 4)
BER : Manufacturing Survey : Full Survey     Full-text available via subscription   (Followers: 2)
BER : Motor Trade Survey     Full-text available via subscription   (Followers: 1)
BER : Retail Sector Survey     Full-text available via subscription   (Followers: 2)
BER : Retail Survey : Full Survey     Full-text available via subscription   (Followers: 2)
BER : Survey of Business Conditions in Manufacturing : An Executive Summary     Full-text available via subscription   (Followers: 3)
BER : Survey of Business Conditions in Retail : An Executive Summary     Full-text available via subscription   (Followers: 3)
Bharatiya Vaigyanik evam Audyogik Anusandhan Patrika (BVAAP)     Open Access   (Followers: 1)
Biofuels Engineering     Open Access  
Biointerphases     Open Access   (Followers: 1)
Biomaterials Science     Full-text available via subscription   (Followers: 9)
Biomedical Engineering     Hybrid Journal   (Followers: 16)
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: 17)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 32)
Biomedical Engineering: Applications, Basis and Communications     Hybrid Journal   (Followers: 5)
Biomedical Microdevices     Hybrid Journal   (Followers: 8)
Biomedical Science and Engineering     Open Access   (Followers: 3)
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  
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: 14)
Bulletin of Engineering Geology and the Environment     Hybrid Journal   (Followers: 3)
Bulletin of the Crimean Astrophysical Observatory     Hybrid Journal  
Cahiers, Droit, Sciences et Technologies     Open Access  
Calphad     Hybrid Journal  
Canadian Geotechnical Journal     Hybrid Journal   (Followers: 14)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 41)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 8)
Case Studies in Thermal Engineering     Open Access   (Followers: 3)
Catalysis Communications     Hybrid Journal   (Followers: 6)
Catalysis Letters     Hybrid Journal   (Followers: 2)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysis Today     Hybrid Journal   (Followers: 7)
CEAS Space Journal     Hybrid Journal  
Cellular and Molecular Neurobiology     Hybrid Journal   (Followers: 3)
Central European Journal of Engineering     Hybrid Journal   (Followers: 1)
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: 1)
CienciaUAT     Open Access  
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: 14)
City, Culture and Society     Hybrid Journal   (Followers: 21)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Clean Air Journal     Full-text available via subscription   (Followers: 2)
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: 3)
Cogent Engineering     Open Access   (Followers: 2)
Cognitive Computation     Hybrid Journal   (Followers: 4)
Color Research & Application     Hybrid Journal   (Followers: 1)
COMBINATORICA     Hybrid Journal  
Combustion Theory and Modelling     Hybrid Journal   (Followers: 13)
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: 26)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Composite Structures     Hybrid Journal   (Followers: 254)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 179)
Composites Part B : Engineering     Hybrid Journal   (Followers: 230)
Composites Science and Technology     Hybrid Journal   (Followers: 171)
Comptes Rendus Mécanique     Full-text available via subscription   (Followers: 2)
Computation     Open Access  
Computational Geosciences     Hybrid Journal   (Followers: 14)
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: 6)
Computer Science and Engineering     Open Access   (Followers: 17)
Computers & Geosciences     Hybrid Journal   (Followers: 28)
Computers & Mathematics with Applications     Full-text available via subscription   (Followers: 5)
Computers and Electronics in Agriculture     Hybrid Journal   (Followers: 4)
Computers and Geotechnics     Hybrid Journal   (Followers: 10)
Computing and Visualization in Science     Hybrid Journal   (Followers: 5)
Computing in Science & Engineering     Full-text available via subscription   (Followers: 30)
Conciencia Tecnologica     Open Access  
Concurrent Engineering     Hybrid Journal   (Followers: 3)
Continuum Mechanics and Thermodynamics     Hybrid Journal   (Followers: 6)
Control and Dynamic Systems     Full-text available via subscription   (Followers: 8)
Control Engineering Practice     Hybrid Journal   (Followers: 42)
Control Theory and Informatics     Open Access   (Followers: 7)
Corrosion Science     Hybrid Journal   (Followers: 25)
CT&F Ciencia, Tecnologia y Futuro     Open Access  
CTheory     Open Access  

        1 2 3 4 5 6 7 | Last

Journal Cover Composites Science and Technology
  [SJR: 1.512]   [H-I: 144]   [171 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0266-3538
   Published by Elsevier Homepage  [3043 journals]
  • A novel fluid-filler/polymer composite as high-temperature thermally
           conductive and electrically insulating material
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Zhaodongfang Gao, Qi Zhao, Chuanbin Li, Shan Wang, Lijie Dong, Guo-Hua Hu, Quanling Yang, Chuanxi Xiong
      Liquid paraffin microcapsules (LPMs) were incorporated into epoxy resin to prepare fluid-filler/polymer composite materials in this work, with the objective of introducing fluid heat convection into thermally conductive and electrically insulting materials. The LPMs were fabricated by coating urea resin onto liquid paraffin via in-situ polymerization, enabling the as-prepared LPMs to experience no weight loss below 240 °C. The heat dissipation efficiency of the LPM/epoxy-resin composite with 25 vol% LPM content was remarkably improved above 50 °C, although its thermal conductivity was only 0.25 W/(m·K) at room temperature. The enhancement of heat dissipation efficiency above 50 °C could be ascribed to the effect of fluid heat convection in the LPM filler increased with increasing temperature. The LPM/epoxy composites containing 20 vol% of LPM filler exhibited tensile strengths, bending strengths, and breaking elongations that were 14.3%, 12.5%, and 30.5% higher, respectively, than those of the pure epoxy resin. The results of this study indicate that fluid heat convention is of great significance in the development of thermally conductive and electrically insulting materials.

      PubDate: 2017-08-03T04:52:18Z
       
  • Three-dimensional tubular graphene/polyaniline composites as
           high-performance elastic thermoelectrics
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Liming Wang, Hui Bi, Qin Yao, Dudi Ren, Sanyin Qu, Fuqiang Huang, Lidong Chen
      Combining thermoelectric (TE) properties and elastic features of organic materials will be unique and fascinating, which is difficult for traditional inorganic TE materials. However, organic materials with good elasticity always show poor electrical conductivity as well as low TE performance. Herein, we composite polyaniline (PANI) with three-dimensional tubular graphene (3D graphene) for high-performance elastic TE materials. It was found this method overcame the commonly encountered dispersing problem of graphene and therefore maximized the amount of the interfaces between graphene and PANI, which contributed to a relatively high Seebeck coefficient and low thermal conductivity. As a result, a maximum ZT value of 0.02 was achieved at room temperature in 55 wt% 3D graphene/PANI composite bulks, which was among the top level for PANI based composite TE bulks. Furthermore, the elastic composite bulks also exhibited mechanical-stable TE properties, with negligible performance change after 100 times 50% compression cycles. It is the first time to fabricate polymer based bulks with such excellent TE properties and elasticity to the best of our knowledge. This work demonstrates a new strategy for preparing high-performance elastic TE materials.

      PubDate: 2017-08-03T04:52:18Z
       
  • Learning from nacre: Constructing polymer nanocomposites
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Chuanjin Huang, Qunfeng Cheng
      Due to the small size and special physical properties of nanometer materials, polymer nanocomposites, combined nanoscale reinforcements with polymer matrix, possess outstanding mechanical properties and functional performances, which play a key role in many fields, especially for application in fields of industry and aerospace. However, poor dispersion and weak interfacial interactions are the critical factors that restrict the great improvement in performance of polymer nanocomposites. Although these issues have been solved in some extent via various methods, such as surfactant adsorption, polymer wrapping, surface modification, it still remains a great challenge for achieving high performance polymer nanocomposites as theoretically expected. Nacre, with 95% (volume fraction) inorganic calcium carbonate and 5% (volume fraction) biopolymers, is a typical binary cooperative complementary material system with hard inorganic component and soft organic matrix. Its typical “brick-and-mortar” hierarchical micro/nano-scale structure provides an excellent guideline for constructing polymer nanocomposites. It skillfully overcomes the bottleneck of traditional approaches for fabricating polymer nanocomposites, such as poor dispersion, low loading, and weak interfacial interactions. Recently, we have successfully demonstrated the bioinspired concept is a successful approach for constructing high performance polymer nanocomposites based on different reinforcement fillers, such as nanoclay, carbon nanotubes, and graphene. The resultant bioinspired polymer nanocomposites (BPNs) show layered hierarchical micro/nano-scale structure and outstanding mechanical properties. This feature article reviews our group's work and other groups' research results on BPNs in recent years, and discuss the advantages of BPNs through comparing with traditional methods, as shown in Fig. 1, including: i) Bioinspired assembly approaches for achieving the homogeneous dispersion and layered structure of reinforcement fillers in polymer matrix, such as layer-by-layer, infiltration, evaporation, freeze casting.; ii) various approaches for designing interfacial interactions; iii) the effect of synergy on the performance of BPNs; iv) representative applications of BPNs, such as energy storage devices, filter, sensors. Finally, this feature article also focuses on a perspective of BPNs, commenting on whether the bioinspired concept is viable and practical for polymer nanocomposites, and on what has been achieved to date. Most importantly, a roadmap of BPNs for near future will be depicted, including integrated mechanical properties and functions, intelligent properties, etc.

      PubDate: 2017-08-03T04:52:18Z
       
  • Controlling the electrical conductivity of fibre-polymer composites using
           z-pins
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): F. Pegorin, K. Pingkarawat, A.P. Mouritz
      Carbon fibre composites have inherently high through-thickness electrical resistivity, which limits their application when high electrical conductivity is required. The use of z-pins to increase the through-thickness electrical conductivity of composite laminates is investigated in this paper. The through-thickness and in-plane electrical properties of a unidirectional carbon-epoxy laminate reinforced with carbon fibre composite or metal (copper, stainless steel, titanium) z-pins are characterised. Experimental tests and analytical model reveal that z-pins can increase the through-thickness electrical conductivity of the composite material by many orders of magnitude (up to 106). The through-thickness electrical conductivity can be controllably increased via the judicious choice of the material type and volume content of the z-pins. Large improvements to the through-thickness conductivity can be achieved without the z-pins altering significantly the in-plane conductivity of the composite material.

      PubDate: 2017-08-03T04:52:18Z
       
  • Improving thermal conductivity of styrene-butadiene rubber composites by
           incorporating mesoporous silica@solvothermal reduced graphene oxide hybrid
           nanosheets with low graphene content
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Zijin Liu, Hongmei Zhang, Shiqiang Song, Yong Zhang
      Styrene-butadiene rubber (SBR) composites with enhanced thermal conductivity (TC) were prepared, by incorporating mesoporous silica@reduced graphene oxide (mSiO2@rGO) hybrid nanosheets. The mSiO2@rGO with sandwich structure is composed of rGO (0.50 wt%) coated with mSiO2. The sandwich and mesoporous features of mSiO2@rGO were clearly characterized. Compared to rGO and mSiO2, the mSiO2@rGO shows synergistic effects on TC enhancement. The incorporation of 3 per hundred rubber (phr) mSiO2@rGO increased the TC of SBR composites to 0.424 Wm−1K−1, which was about 183% of the TC of neat SBR (0.232 Wm−1K−1). Moreover, compared to the reported silica@graphene hybrid, mSiO2@rGO has mesoporous framework with pore sizes about 8.9 nm. The mSiO2 coating on rGO acts as functional block which could impede the aggregation of rGO, decrease the modulus mismatch between rGO and SBR, and increase the interface interaction between rGO and SBR.

      PubDate: 2017-08-03T04:52:18Z
       
  • Influence from defects of three-dimensional graphene network on
           photocatalytic performance of composite photocatalyst
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Bo Tang, Haiqun Chen, Yanfeng He, Zhengwei Wang, Jun Zhang, Jinping Wang
      Three-dimensional graphene networks (3DGN) with various defect densities prepared by chemical vapor deposition method are adopted to modify TiO2 for high photocatalytic performances. Based on the obtained decomposition rate constants of phenol and Rhodamine-B, the photocatalytic activities of the resulting composite photocatalysts are found closely related to the defect density of the adopted 3DGN, which is proven by the electron paramagnetic resonance spectroscopy and tunneling electron microscope. It is revealed that the surface defects of the 3DGN can play as active sites to effectively adsorb pollutants, which is the key premise for the following decomposition process. Moreover, these defects further play as a bridge to achieve a close contact between the 3DGN and TiO2, enhancing electron transport ability between them. By adopting the 3DGN with a moderate defect density, photocatalytic performance of the resulting photocatalyst is significantly enhanced under both UV- and visible-light illumination, demonstrating that optimizing the employed 3DGN is an effective approach to enhance the photocatalytic activity of TiO2.

      PubDate: 2017-07-23T22:12:28Z
       
  • Three-phase PANI@nano-Fe3O4@CFs heterostructure: Fabrication,
           characterization and investigation of microwave absorption and EMI
           shielding of PANI@nano-Fe3O4@CFs/epoxy hybrid composite
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Farid Movassagh-Alanagh, Aidin Bordbar-Khiabani, Amin Ahangari-Asl
      In this work, a three phase carbon fiber (CF)-based electromagnetic (EM) wave absorbing and EM interference (EMI) shielding heterostructure was fabricated through a layer by layer assembly. The nano-Fe3O4 particles were deposited on CFs via a modified multi-step electrophoretic deposition (EPD). The PANI@nano-Fe3O4@CFs heterostructures were prepared using an in situ polymerization process of polyaniline (PANI) on nano-Fe3O4@CFs in HCl solution. The results showed that the PANI@nano-Fe3O4@CFs mats with a layer by layer (LBL) assembly were successfully fabricated. The saturated magnetization (Ms) of the as-synthesized nano-Fe3O4 powder decreased from 72.612 to 8.934 emu/g for the nano-Fe3O4@CFs and from 8.934 to 0.191 emu/g for the PANI@nano-Fe3O4@CFs mats due to the reduction in the effective mass/volume percentage of nano-Fe3O4 particles in the composites. The fabricated epoxy-based hybrid composites filled with PANI@nano-Fe3O4@CFs segments exhibited both of the dielectric and magnetic losses at the 8.2–18 GHz frequency range. The composite containing 1 wt% of PANI@nano-Fe3O4@CFs with the thickness of 1.5 mm showed a maximum reflection loss (RL) value of −11.11 dB with an effective absorption bandwidth of about 6 GHz in the frequency range of 8.2–18 GHz. Also, the sample filled with 5 wt % of EM wave absorbing segments with the thickness of 3 mm demonstrated an EMI shielding effectiveness (SE) value of 29 dB at the same frequency range.

      PubDate: 2017-07-23T22:12:28Z
       
  • Enhanced alignment and mechanical properties through the use of
           hydroxyethyl cellulose in solvent-free native cellulose spun filaments
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Saleh Hooshmand, Yvonne Aitomäki, Linn Berglund, Aji P. Mathew, Kristiina Oksman
      In this study, the addition of hydroxyethyl cellulose (HEC) in cellulose nanofiber filaments is shown to improve the solvent-free processing and mechanical properties of these biobased fibers as well as their compatibility with epoxy. An aqueous dope of cellulose nanofiber (CNF) with HEC was spun and the resulting filaments cold-drawn. The HEC increased the wet strength of the dope allowing stable spinning of low concentrations of CNF. These lower concentrations promote nanofiber alignment which is further improved by cold-drawing. Alignment improves the modulus and strength and an increase of over 70% compared to the as-spun CNF only filaments was achieved. HEC also decreases hydrophilicity thus increasing slightly the interfacial shear strength of the filaments with epoxy resin. The result is continuous biobased fibers with improved epoxy compatibility that can be prepared in an upscalable and environmentally friendly way. Further optimization is expected to increase draw ratio and consequently mechanical properties.

      PubDate: 2017-07-23T22:12:28Z
       
  • Scale effect on tribo-mechanical behavior of vegetal fibers in reinforced
           bio-composite materials
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Faissal Chegdani, Mohamed El Mansori, Sabeur Mezghani, Alex Montagne
      The nature of friction of vegetal fiber and polymeric matrix in bio-composite materials is very important for many industrial applications. In order to design natural fiber composites for structural applications, the scientific understanding of tribo-mechanical phenomena inside the heterogeneous structure of natural fibers and also the overall heterogeneous structure of the bio-composite is required. This implies a special focus on the fundamental aspects of vegetal fiber friction at the macro-, meso-, and microscale. This research paper investigates the multiscale mechanical and friction properties of natural fibers. The mechanical properties of flax fibers, glass fibers (as a reference) and polypropylene matrix has been evaluated at microscale and mesoscale by Atomic Force Microscopy (AFM) and Nanoindenter XP (MTS Nano Instruments), respectively, using nanoindentation technique. At the macroscale, the mechanical behavior has been considered for the global composite structure. The micro-friction response of each composite component has been measured by instrumenting AFM for scratch test technique. The results show the scale dependence of mechanical behavior for flax fibers, unlike glass fibers and polypropylene matrix where their mechanical performances are independent of the analysis scale. Tribological results in terms of dynamic friction coefficient show that flax fibers induce more friction than glass fibers, while polypropylene matrix generates the highest friction. This is sign that vegetal fiber friction is scale dependent property as shown when referring to the contact mechanics theory. The arisen results are very important for many technical applications in PMCs surface engineering based on plant fibers.

      PubDate: 2017-07-23T22:12:28Z
       
  • Prediction and experiment on the compressive property of the sandwich
           structure with a chevron carbon-fibre-reinforced composite folded core
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Yuguo Sun, Yanxiao Li
      The compressive performances of carbon-fibre-reinforced composite sandwich panels with chevron folded cores were investigated in this paper. Analytical expression based on energy approach were derived to predict their compressive elastic modulus and strength. The sandwich panels with specific fibre orientation cores were manufactured and tested to reveal the influences of fibre ply angles on the responses for compressive loading. The stiffness and strength increased distinctly with the 0° fibre orientation increments. The predictions for compressive stiffness and strength showed good agreement with the measurements, and the failure mechanisms of the structures were discussed by simulation analysis.

      PubDate: 2017-07-23T22:12:28Z
       
  • Characterization of residual stress and deformation in additively
           manufactured ABS polymer and composite specimens
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Wei Zhang, Amanda S. Wu, Jessica Sun, Zhenzhen Quan, Bohong Gu, Baozhong Sun, Chase Cotton, Dirk Heider, Tsu-Wei Chou
      Residual stresses induced in the layer-by-layer fabrication process of additively manufactured parts have significant impact on their mechanical properties and dimensional accuracy. This work aims to characterize the residual stress and deformation in specimens based on unreinforced acrylonitrile-butadiene-styrene (ABS), carbon nanotube reinforced ABS and short carbon fiber reinforced ABS. The shrinkage and displacement fields were obtained, respectively, by thermal treatment as well as Digital Image Correlation observation of specimens before and after sectioning. The microstructure and porosity of additively manufactured specimens were also examined using X-ray micro-computed tomography. Specimen shrinkage and porosity content were significantly influenced by the process parameters of raster angle and printing speed, as well as material types. Faster printing speed led to larger porosity and residual stress, as well as higher shrinkage after specimen thermal treatment. Raster angle had a greater influence on specimen shrinkage and porosity as comparing to printing speed. Composite printing wires based on carbon nanotube and short carbon fiber in ABS greatly reduced specimen shrinkage and deformation, while increased the porosity, especially for carbon fiber reinforced ABS specimens.

      PubDate: 2017-07-23T22:12:28Z
       
  • Local surface mechanical properties of PDMS-silica nanocomposite probed
           with Intermodulation AFM
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): H. Huang, I. Dobryden, P.-A. Thorén, L. Ejenstam, J. Pan, M.L. Fielden, D.B. Haviland, P.M. Claesson
      The mechanical properties of polymeric nanocomposites are strongly affected by the nature of the interphase between filler and matrix, which can be controlled by means of surface chemistry. In this report, we utilize intermodulation atomic force microscopy (ImAFM) to probe local mechanical response with nanometer-scale resolution of poly(dimethylsiloxane) (PDMS) coatings with and without 20 wt% of hydrophobic silica nanoparticles. The data evaluation is carried out without inferring any contact mechanics model, and is thus model-independent. ImAFM imaging reveals a small but readily measurable inhomogeneous mechanical response of the pure PDMS surface layer. The analysis of energy dissipation measured with ImAFM showed a lowering of the viscous response due to the presence of the hydrophobic silica nanoparticles in the polymer matrix. An enhanced elastic response was also evident from the in-phase stiffness of the matrix, which was found to increase by a factor of 1.5 in presence of the nanoparticles. Analysis of dissipation energy and stiffness in the immediate vicinity of the nanoparticles provides an estimate of the interphase thickness. Because the local stiffness varies significantly near the nanoparticle, AFM height images contain artifacts that must be corrected in order to reveal the true surface topography. Without such a correction the AFM height images erroneously show that the stiff particles protrude from the surface, whereas corrected images show that they are actually embedded in the matrix and likely covered with a thin layer of polymer.

      PubDate: 2017-07-23T22:12:28Z
       
  • The effect of dopamine modified titanium dioxide nanoparticles on the
           performance of Poly (vinyl alcohol)/titanium dioxide composites
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Feifei Deng, Yu Guan, Zhiqing Shi, Fei Wang, Xinyuan Che, Yawei Liu, Yinghan Wang
      In order to improve the dispersion of nanoparticles (NPs) and enhance the interfacial interactions between NPs and Poly (vinyl alcohol) (PVA) matrix, the surface of titanium dioxide (TiO2) was modified by green and biocompatible dopamine (DA). PVA composites containing TiO2 or modified TiO2 (DA-TiO2) were fabricated through simple one-step method. The as-prepared composites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), tensile experiments and thermogravimetric analysis (TGA). The TEM images demonstrated that DA-TiO2 NPs were dispersed well in the PVA matrix, which may originate from the hydrogen bonding and covalent bond formed between PVA and DA-TiO2 NPs. The tensile experiments exhibited significant improvement for the mechanical properties of PVA composites with proper amount of DA-TiO2 NPs. Especially, the PVA composites with 1 wt% DA-TiO2 NPs displayed the desired consequences in terms of tensile strength and toughness, compared to the pure PVA, which were increased by 47.9% and 145.2%, respectively. The TGA curves showed that DA-TiO2 NPs enhanced the thermal stability of PVA. Additionally, PVA/DA-TiO2 composite showed relatively good optical transparency and water resistance.

      PubDate: 2017-07-23T22:12:28Z
       
  • Wet and dry flexural high cycle fatigue behaviour of fully bioresorbable
           glass fibre composites: In-situ polymerisation versus laminate stacking
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Menghao Chen, Jiawa Lu, Reda M. Felfel, Andrew J. Parsons, Derek J. Irvine, Christopher D. Rudd, Ifty Ahmed
      Fully bioresorbable phosphate based glass fibre reinforced polycaprolactone (PCL/PGF) composites are potentially excellent candidates to address current issues experienced with use of metal implants for hard tissue repair, such as stress shielding effects. It is therefore essential to investigate these materials under representative loading cases and to understand their fatigue behaviour (wet and dry) in order to predict their lifetime in service and their likely mechanisms of failure. This paper investigated the dry and wet flexural fatigue behaviour of PCL/PGF composites with 35% and 50% fibre volume fraction (Vf). Significantly longer flexural fatigue life (p < 0.0001) and superior fatigue damage resistance were observed for In-situ Polymerised (ISP) composites as compared to the Laminate Stacking (LS) composites in both dry and wet conditions, indicating that the ISP promoted considerably stronger interfacial bonding than the LS. Immersion in fluid (wet) during the flexural fatigue tests resulted in significant reduction (p < 0.0001) in the composites fatigue life, earlier onset of fatigue damage and faster damage propagation. Regardless of testing conditions, increasing fibre content led to shorter fatigue life for the PCL/PGF composites. Meanwhile, immersion in degradation media caused softening of both LS and ISP composites during the fatigue tests, which led to a more ductile failure mode. Among all the composites that were investigated, ISP35 (35% Vf) composites maintained at least 50% of their initial stiffness at the end of fatigue tests in both conditions, which is comparable to the flexural properties of human cortical bones. Consequently, ISP composites with 35% Vf maintained at least 50% of its flexural properties after the fatigue failure, which the mechanical retentions were well matched with the properties of human cortical bones.
      Graphical abstract image

      PubDate: 2017-07-12T12:22:19Z
       
  • Enhancing the neutron shielding ability of polyethylene composites with an
           alternating multi-layered structure
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Xianlong Zhang, Mingtao Yang, Xiaomeng Zhang, Hong Wu, Shaoyun Guo, Yuzhong Wang
      Neutron radiation is often encountered in a wide range of industries, such as aerospace, healthcare and nuclear power plants. It has been an arduous challenge to shield this neutron radiation to improve equipment safety and protect human health. In order to make an effective neutron shielding material, alternating multi-layered composites (high density polyethylene)/(high density polyethylene/boron nitride), (HDPE/(HDPE/BN)) and (HDPE/BN)/(HDPE/Barium sulfate (BaSO4)) were fabricated using a multi-layered co-extrusion system. The HDPE/BN layers in the alternating multilayered HDPE/(HDPE/BN) and (HDPE/BN)/(HDPE/BaSO4) composites had a continuous and layered distribution in their structure, with the BN particles oriented in the extrusion direction. The probability of collision between incident photons and flake-shaped particles is enhanced through alignment of the oriented BN particles. In this way, neutron transmittance noticeably decreased with an increasing number of layers. Compared to traditional polymer-blended materials, the alternating multilayered composites showed excellent shielding efficiency. In addition, the results of the dynamic rheological analysis showed that alternating multi-layered composites with more layers can weaken the cross-linking effects induced by secondary radiation. Furthermore, according to the Nano-TA analysis, BaSO4 was an effective shield of secondary radiation, so the average melting point, in nanoscale, can be represented as follows: (Nano- T m ¯ ) ((HDPE/BN)/(HDPE/BaSO4)) > Nano- T m ¯ (HDPE/(HDPE/BN)).

      PubDate: 2017-07-12T12:22:19Z
       
  • Electrical conductivity and mechanical properties of melt-spun ternary
           composites comprising PMMA, carbon fibers and carbon black
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Muchao Qu, Fritjof Nilsson, Yijing Qin, Guanda Yang, Yamin Pan, Xianhu Liu, Gabriel Hernandez Rodriguez, Jianfan Chen, Chunhua Zhang, Dirk W. Schubert
      In this study, the electrical conductivity of melt spun composites consisting of PMMA containing both aligned carbon fibers (CF) and carbon black (CB) has been investigated. A broad range of composite compositions (up to 50 vol % CF and 20 vol % CB) was studied. The percolation thresholds of binary PMMA/CF and PMMA/CB composites were determined to 31.8 and 3.9 vol %, respectively. Experimental conductivity contour plots for PMMA/CF/CB ternary composites were presented for the first time. Additionally, based on a model for predicting the percolation threshold of ternary composites, a novel equation was proposed to predict the conductivity of ternary composites, showing results in agreement with corresponding experimental data. Finally, two mechanical contour plots for elastic modulus and tensile strength were presented, showing how the decreasing tensile strength and increasing E-modulus of the PMMA/CF/CB ternary composites was depending on the CB and CF filling fractions. The systematic measurements and novel equations presented in this work are especially valuable when designing ternary conductive polymer composites with two different fillers.

      PubDate: 2017-07-12T12:22:19Z
       
  • Damage and failure of triaxial braided composites under multi-axial stress
           states
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Tobias Wehrkamp-Richter, Roland Hinterhölzl, Silvestre T. Pinho
      Damage and failure of triaxial braided composites under multi-axial stress states was investigated. In order to introduce different multi-axial stress states in the material, uni-axial tensile tests were performed at different off-axis orientations. Three braid architectures, comprising braiding angles of 30 ° , 45 ° and 60 ° were each loaded parallel to their axial, transverse and braid yarn direction. Digital image correlation measurement techniques were used to quantify the effects of the textile architecture and its heterogeneity on the strain field, to identify and locate constituent failure mechanisms and to investigate damage initiation and development. In order to identify the driving physical mechanisms behind the material non-linearity, the evolution of the damage variable and the accumulated inelastic strain was quantified using incremental loading/unloading experiments. A high-speed camera was employed in order to study the dynamic nature of catastrophic failure. The triaxial braids within this study exhibited severe non-linearities in the mechanical response before final failure as a result of extensive matrix cracking. While we found the underlying textile architecture to slightly reduce the elastic properties compared to equivalent tape laminates, it functions as a natural crack arresting grid. As a result of this mechanism, braids under certain load conditions were capable of withstanding a higher strain to failure, even if a large portion of the specimen surface was saturated with matrix cracks. The accompanying mechanical behaviour can be desirable in the design of crash absorbing or pseudo-ductile materials. An additional failure mode intrinsic to the textile architecture was encountered for loading in the heavily undulated braid yarn direction. Due to yarn straightening and out-of-plane movements, braided composites were found to fail as a result of large scale delaminations accompanied by progressive fibre bundle pull-out.

      PubDate: 2017-07-12T12:22:19Z
       
  • Silver nanowire/carbon nanotube/cellulose hybrid papers for electrically
           conductive and electromagnetic interference shielding elements
    • Abstract: Publication date: 29 September 2017
      Source:Composites Science and Technology, Volume 150
      Author(s): Hyeong Yeol Choi, Tae-Won Lee, Sang-Eui Lee, JaeDeok Lim, Young Gyu Jeong
      We report the microstructures, electrical conductivity, and electromagnetic interference (EMI) shielding effectiveness of a series of hybrid cellulose papers coated alternatively with silver nanowire (AgNW) and multi-walled carbon nanotube (MWCNT), which are fabricated by controlling the dip-coating sequence and cycle. SEM images and EDS data reveal that AgNWs and/or MWCNTs are sequentially coated on the surfaces of the cellulose papers with increasing the dip-coating cycle and the coating density of the particles decreases gradually in thickness direction of the papers. This result is supported by the anisotropic apparent electrical conductivity of AgNW/MWCNT/cellulose hybrid papers in in-plane and thickness directions. In addition, the apparent electrical conductivity of the hybrid papers in the in-plane direction increases significantly from 0.17–0.22 S/cm to 2.55–2.83 S/cm with increasing the coating cycle from 2 to 10, although it is higher for the hybrid cellulose papers with AgNW top-coating layers than the hybrid papers with MWCNT top-coating layers at the same coating cycle. This result indicates that a highly effective and conductive AgNW/MWCNT network is formed on the cellulose fibers in a layer-by-layer manner. For the hybrid papers with 2.55–2.83 S/cm, high EMI shielding effectiveness of ∼23.8 dB at 1 GHz is achieved.

      PubDate: 2017-07-12T12:22:19Z
       
  • Composite models for compression moulded long regenerated cellulose
           fibre-reinforced brittle polylactide (PLA)
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Nina Graupner, Gerhard Ziegmann, Jörg Müssig
      The present study shows a new approach for the prediction of tensile strength values of compression moulded long cellulose fibre-reinforced brittle polylactide (PLA) composites. For this approach regenerated cellulose fibres (lyocell) of variable fineness were used as reinforcement. Composites with different fibre loadings (17, 26 and 36 vol-%) and mean fibre orientation angles ranging between ± 20 and ± 65° were manufactured. Some published models were applied to the mechanical properties of our composites. While the rule of mixture as well as the Kelly-Tyson model lead to a clear overestimation of the strength values, the model of Taha & El-Sabbagh et al. (developed for injection moulded composites) leads to a clear underestimation. On the basis of the Kelly-Tyson-model expanded with Taha & El-Sabbagh et al.'s agglomeration factor and the use of the fibre stress at the point of elongation at break of the composite a new model was created for compression moulded regenerated cellulose fibre-reinforced composites. Overall, 19 different composites were investigated. 13 of them show a deviation from the model data to the measured tensile strength of < ± 10%, 4 of them between - 10% and −15% and only 2 of them have shown a deviation of −16 and −18%, respectively.

      PubDate: 2017-07-12T12:22:19Z
       
  • Comparative low-velocity impact behavior of bio-inspired and conventional
           sandwich composite beams
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): S.H. Abo Sabah, A.B.H. Kueh, M.Y. Al-Fasih
      A novel woodpecker's head-inspired sandwich beam, comprising carbon fiber laminated skins with rubber and aluminum honeycomb cores, was developed for low-velocity impact behavior improvement. A comparative study against conventional sandwich beam was performed employing three impact energy levels (7.28 J, 9.74 J, 12.63 J) by means of experimental and numerical methods. In all cases, bio-inspired beams were consistently superior to those conventional, with low developed stress, deformation, and damage area while carrying higher maximum impact force. Even with a low added mass, the impact resistance efficiencies of the bio-inspired beams were 2.7–5.7 times greater than those of conventional configuration, thus exhibiting an improved impact performance of the developed bio-inspired beam useful for future protection strategy.

      PubDate: 2017-07-12T12:22:19Z
       
  • Degradation and recovery of graphene/polymer interfaces under cyclic
           mechanical loading
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Guorui Wang, Enlai Gao, Zhaohe Dai, Luqi Liu, Zhiping Xu, Zhong Zhang
      Interface failure is a common phenomenon for conventional composite materials when subjected to repeated mechanical loads, and it tends to be critical for nanocomposites due to several orders of magnitude enhancement in interfacial area. Herein, the graphene/poly(methyl methacrylate) (PMMA) interface when subjected to cyclic loading conditions exhibits obvious mechanical degradation through interfacial sliding, which has received little attention yet. Through a joint study of experimental tests and molecular dynamics simulations, the interface weakening is attributed to the formation of graphene buckles that not only reduces the interfacial contact area but also impairs the overall interfacial load transfer. However, reminiscent of the shape memory effect that is commonly triggered by temperature, conformational transition at the interfaces exhibits remarkable mechanical recovery under a moderate thermal stimulus, manifested by the interface reconstruction activated by van der Waals (vdW) forces. These findings elucidate the complex interactions between matrix and nanostructures in composite materials under cyclic loading conditions, and control over this mechanism could provide guidelines upon chemical design through tailoring the interfacial adhesion for specific applications.

      PubDate: 2017-07-12T12:22:19Z
       
  • Synergistic toughening of polymer nanocomposites by hydrogen-bond assisted
           three-dimensional network of functionalized graphene oxide and carbon
           nanotubes
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Ki-Ho Nam, Jaesang Yu, Nam-Ho You, Haksoo Han, Bon-Cheol Ku
      We report a facile method to enhance mechanical properties of polymer nanocomposites using three-dimensional (3D) network structures of functionalized graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) in a polymer matrix. The GO and MWCNTs were functionalized using Fisher indole and diazonium-salt reactions to produce pyridine (Py) moiety on the GO and MWCNTs. The functionalized GO (Py-RGO) and MWCNT (Py-MWCNT) nanocomposites exhibited hydrogen-bond assisted 3D network structures in a polyimide (PI) matrix. By incorporating 1 wt% of carbon materials (0.9 wt% Py-RGO and 0.1 wt% Py-MWCNTs) in a PI, the tensile strength and modulus of the ternary nanocomposites reached 581 MPa and 31 GPa, respectively, which was an enhancement of 221% and 312% compared with pristine PI. The fracture energy of the PI/Py-RGO/Py-MWCNT nanocomposites improved 200% and approached 29.7 MJ m−3. The formation of the 3D network structure of the functionalized carbon nanomaterials is considered to significantly affect load transfer of nanofillers in the polymer matrix, and produce high performance polymer nanocomposites.
      Graphical abstract image

      PubDate: 2017-07-12T12:22:19Z
       
  • Three-dimensional mesoscale modelling of concrete composites by using
           random walking algorithm
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Zihua Zhang, Xiaogang Song, Yan Liu, Di Wu, Chongmin Song
      The mechanical performance of concrete is primarily dominated by the characteristics and interrelation of its ingredients, especially the content, shape and grading of coarse aggregates. Consequently, constructing a realistic mesostructure of concrete is essential for adequate mesoscale studies on the corresponding mechanical properties. In this study, a novel three-dimensional coarse aggregate generation scheme, namely the random walking algorithm (RWA), is proposed for constructing physically feasible mesostructures of concrete. The proposed approach is able to generate a series of aggregates within an initial placing domain, and subsequently, move them into the target domain by both translation and rotation. Within the proposed analysis framework, the high compactness of mesostructures with an improved aggregate content can be robustly achieved by randomly shifting previously placed aggregates, such that the later generated ones can be ingeniously blended in. Typical samples of random aggregate structure (RAS) are generated under specified grading curves. Parameters relating to aggregate content and efficiency of modelling are critically evaluated. By thoroughly investigating practically motivated examples, it is evidently illustrated that the present method is capable of obtaining a relatively realistic and random distribution of coarse aggregates, and more importantly, the grading of the generated aggregate samples is in compliance with the Fuller's Curve.

      PubDate: 2017-07-12T12:22:19Z
       
  • Broadband dynamic responses of flexible carbon black/poly (vinylidene
           fluoride) nanocomposites: A sensitivity study
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Hao Xu, Zhihui Zeng, Zhanjun Wu, Limin Zhou, Zhongqing Su, Yaozhong Liao, Menglong Liu
      Nanocomposites fabricated based on a compound of carbon nanofiller and polymer matrix exhibit extraordinary piezoresistive performance, and the capacity of nanocomposite sensors in measuring structural dynamic strains has been widely demonstrated. However, the sensitivity of existing nanocomposite strain sensors is limited, particularly in aspects of sensing precision and response frequency. This study focuses on sensitivity investigations of flexible nanocomposite sensors fabricated using a compound of carbon black (CB) fillers and polyvinylidene fluoride (PVDF) matrix, which has shown promising potential in perceiving extremely weak strain signals within a considerably broad range of response frequencies. As a highly important indication of sensitivity, sensing precision was characterized in a quantitative manner. Broadband spectrum analysis was conducted as an effective way to examine sensor performance in perceiving minimal disturbances in dynamic strains. Disturbances were generated in two experiments, by introducing local material and geometric variations into the inspected structures, in terms of mass attachment and structural damage. The effectiveness of the nanocomposites in structural damage detection was demonstrated. Moreover, the experimental results indicate the promising potential of nanocomposite-based strain sensors for applications such as advanced bioelectronics, ultrasonic inspection, and in-situ structural health monitoring.

      PubDate: 2017-07-12T12:22:19Z
       
  • Development of conductive paraffin/graphene films laminated on
           fluoroelastomers with high strain recovery and anti-corrosive properties
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Luca Valentini, Silvia Bittolo Bon, Miguel-Angel Lopez-Manchado, Lorenzo Mussolin, Nicola Pugno
      Parafilm is a soft, solvent-proof and self-sealant thermoplastic material obtained by blending paraffin wax and polyolefin and that displays irreversible elongational thinning as the material is stretched. In this paper a lamination process was used to transfer graphene nanoplatelets (GNPs) on self-adherent Parafilm substrate and we show that a high-strain state of such conductive Parafilm/GNPs film is reversible when the film is transferred by lamination to a fluoroelastomer (FKM) substrate. The stretching of GNP network stuck on viscoelastic Parafilm gave rise to regions of high and low GNP concentrations with increasing the electrical resistance upon stretching. Upon relaxation from a high-strain state, the composite film on FKM substrate maintain the initial electrical conductive state. Finally it was shown the reduction of the ethanol corrosion action in terms of swelling and mechanical performance of the neat FKM when the Parafilm/GNPs film is used for its packaging. In view of the low cost thermoplastic polymer used for the transferring and the lamination method proposed, these findings represent a facile and an industrial scalable approach to realize novel multifunctional elastomer composites.

      PubDate: 2017-07-12T12:22:19Z
       
  • Fabrication and properties of graphene oxide-grafted-poly(hexadecyl
           acrylate) as a solid-solid phase change material
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Ruirui Cao, Haihui Liu, Sai Chen, Dongfang Pei, Jinlei Miao, Xingxiang Zhang
      A novel shape-stabilized solid-solid phase change material of graphene oxide-grafted-poly(hexadecyl acrylate) (GO-g-PHDA) was fabricated by hexadecyl acrylate (HDA) covalently bonding to GO nanosheets via in free radical polymerization (FRP). The evidences of various spectroscopic and microscopic confirm the successful grafting of PHDA onto the surfaces of GO. Thermal energy storage properties and stability of GO-g-PHDA were determined by DSC and TGA. The melting and freezing points are 35.0 and 30.5 °C, respectively. The latent heats of melting and freezing are 79 and 77 J g−1, respectively. The degradation temperature (T0.05) is approximately 214.4 °C, which is much higher than the working temperature region for energy storage applications.

      PubDate: 2017-07-12T12:22:19Z
       
  • A multi-physics process model for simulating the manufacture of
           resin-infused composite aerostructures
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Robert S. Pierce, Brian G. Falzon, Mark C. Thompson
      The increasing demand for large, complex and low-cost composite aerostructures has motivated advances in the simulation of liquid composite moulding techniques with textile reinforcement materials. This work outlines the development and validation of a multi-physics process model that better simulates infusion behaviour through a complex preform compared with traditional models used in industry that do not account for fabric deformation. By combining the results of a preform draping model with deformation-dependent permeability properties, the shape and local flow characteristics of a deformed textile reinforcement have been more realistically defined for infusion. Simulated shear deformation results were used to define the distributed permeability properties across the fabric domain of the infusion model. Full-scale vacuum infusion experiments were conducted for a complex double dome geometry using a plain weave carbon fibre material. The multi-physics process model showed significant improvement over basic models, since it is able to account for the change in flow behaviour that results from local fabric deformation.

      PubDate: 2017-07-12T12:22:19Z
       
  • High-strength graphene and polyacrylonitrile composite fiber enhanced by
           surface coating with polydopamine
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Hyunsoo Kim, Rouhollah Jalili, Geoffrey M. Spinks, Gordon G. Wallace, Seon Jeong Kim
      Carbon fibers are well-known reinforcing elements in advanced composites, but these materials remain expensive partly due to the complex processing methods used to form high strength and high modulus fibers. Graphene is seen as an alternative precursor for the formation of high strength carbon-based fibers. Here it is shown that the strength and modulus of graphene-based fibers are enhanced by incorporating a polyacrylonitrile (PAN) binder, surface coating with polydopamine (PDA) and through appropriate pyrolysis heat treatments. Fiber samples were prepared by a wet-spinning method such that the composition of liquid-crystalline graphene oxide (LCGO) and PAN could be varied over the full range. The maximum fiber mechanical strength (220 MPa) and modulus (19 GPa) occurred at a composition of LCGO (80 wt%) and PAN (20 wt%). The mechanical strength was further significantly increased to 526 MPa through pyrolysis of the LCGO/PAN fiber at 800 °C in a nitrogen atmosphere which caused carbonization of PAN. In addition, surface treatment of the LCGO/PAN fiber with PDA before carbonization improved the mechanical strength by an additional 40%.

      PubDate: 2017-07-12T12:22:19Z
       
  • Stochastic modeling of through the thickness permeability variation in a
           fabric and its effect on void formation during Vacuum Assisted Resin
           Transfer Molding
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Minyoung Yun, Tess Carella, Pavel Simacek, Suresh Advani
      Resin flow during Vacuum Assisted Resin Transfer Molding (VARTM) process, when distribution media (DM) is placed on top of the reinforcement, is largely affected by variation in through the thickness permeability of a woven fabric. The variation in permeability is due to the random pinhole regions around the junctions of fiber tows as they are woven together to form a fabric preform. We characterize and model this pinhole effect on resin flow with the aim of exploring the role of DM permeability (K DM) on void formation. It was found that percentage of voids increases with higher K DM. Five hundred simulations were executed for low, medium and high K DM values and their effect on resin flow and void formation was investigated. Twenty experiments for each DM case were conducted. Flow along the bottom surface was recorded with time. It was observed that the flow front along the bottom became more uneven and irregular with higher K DM, which resulted in higher percentage of voids formed during the process. The numerical simulations qualitatively and quantitatively agreed with the experimentally measured behavior exhibiting higher percentage of unfilled region with increasing DM permeability.

      PubDate: 2017-07-02T12:08:05Z
       
  • Interfacial adhesion properties of carbon fiber/polycarbonate composites
           by using a single-filament fragmentation test
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Ting-Ting Yao, Gang-Ping Wu, Chang Song
      To reveal the interfacial adhesion nature between a carbon fiber (CF) and its surrounding polycarbonate (PC) matrix, the carbon fibers were electrochemically oxidized to differentiate the surface roughness and chemistry status. The fiber surfaces were characterized by SEM, XPS, AFM and dynamic contact angle measurements. Both surface-coating and hot-pressing methods were adopted to prepare specimens for evaluating the CF/PC interfacial adhesion properties by single-filament fragmentation tests. The surface-coating method gave a relatively weak interfacial shear strength (IFSS) result, which varied almost monotonously with the fiber surface roughness, suggesting that in this case the interfacial properties should be dominated by a mechanical interlocking mechanism. However, the hot-pressing process gave a 46–81% higher IFSS result than the solution-coating one, and the IFSS data increased almost linearly with polar component of the carbon fiber surface energy. It was very possible that the interfacial adhesion properties were largely controlled by the chemical reactions (e.g., ester-exchange reaction) at high temperature, which were easy to occur in the presence of oxygenated functionalities at CF surfaces.

      PubDate: 2017-07-02T12:08:05Z
       
  • Enhancing fatigue resistance and damage characterisation in
           adhesively-bonded composite joints by carbon nanofibres
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Raj B. Ladani, Shuying Wu, Anthony J. Kinloch, Kamran Ghorbani, Adrian P. Mouritz, Chun H. Wang
      In the present work we report on the use of carbon nanofibres (CNFs) to simultaneously improve the cyclic fatigue resistance and the detectability of disbonding in adhesively-bonded structures made of carbon-fibre reinforced-plastic (CFRP) composites. The effects of the concentration of the CNFs (i.e. 0.4, 0.7 and 1.0 wt%) and their orientation (i.e. random versus aligned) in the epoxy-adhesive layer between two CFRP substrates are investigated. The results show that increasing the concentration of randomly-oriented CNFs (a) improves greatly the mode I fatigue resistance of the adhesive layer, including raising the crack growth threshold of the cyclic strain-energy release-rate, and (b) increases the quasi-static fracture toughness. Further improvements in the fatigue resistance occur when the CNFs are aligned perpendicular to the plane of the joint, i.e. normal to the crack plane, as opposed to being randomly-oriented in the adhesive layer. In addition, the CNFs form a conductive network that makes it possible to detect and characterise fatigue-induced disbonding using an electrical-resistance technique. A simple model is developed for the relationship between the disbond (i.e. crack size) and the electrical resistance of a bonded joint with conductive substrates. Finite element analyses are carried out to quantify the applicability of this model as a function of the conductivity of the adhesive from 10−4 S/m to 1 S/m. The results confirm that the proposed simple model is highly accurate for joints where the composite substrates have a through-thickness electrical conductivity exceeding a hundred times that of the adhesive. This research paves the way for new multi-functional adhesives with greatly enhanced fatigue resistance and disbond detection capability.

      PubDate: 2017-07-02T12:08:05Z
       
  • Design of flexible PVDF/NaNbO3/RGO nanogenerator and understanding the
           role of nanofillers in the output voltage signal
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Huidrom Hemojit Singh, Simrjit Singh, Neeraj Khare
      Flexible PVDF/NaNbO3/RGO thin films have been synthesized and its application in nanogenerator has been explored. In order to understand the effect of the addition of nanofillers NaNbO3 and RGO in PVDF, we have also synthesized and studied PVDF/RGO and PVDF/NaNbO3 nanocomposite films. Even though the β-phase contents are nearly same in the three nanocomposite films, it has been found that the output voltage generated from PVDF/NaNbO3/RGO nanocomposite film based nanogenerator is maximum (∼2.16 V) with a short circuit current of 0.383 μA. It has been concluded that NaNbO3 nanorods help in the alignment of the electric dipoles in PVDF and also due to the inherent piezoelectric property, it contributes in the overall piezoelectric property of the film. On the other hand presence of RGO helps to move the charges generated inside the film and further allow the dipoles of PVDF to align which leads to enhanced piezoresponse.
      Graphical abstract image

      PubDate: 2017-07-02T12:08:05Z
       
  • Effect of localization of carbon nanotubes on fracture behavior of
           un-vulcanized and dynamically vulcanized PP/EPDM/MWCNT
           blend-nanocomposites
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Mehrdad Khodabandelou, Mir Karim Razavi Aghjeh, Hossein Ali Khonakdar, Majid Mehrabi Mazidi
      Effect of localization of multiwall carbon nanotube (MWCNT) on the fracture toughness and deformation mechanisms of un-vulcanized and dynamically vulcanized polypropylene/ethylene-propylene terpolymer/multiwall carbon nanotube (PP/EPDM/MWCNT) blend-nanocomposites were investigated under both the Izod impact loading and the essential work of fracture (EWF) test as quasi-static loading conditions. The localization of MWCNT in the PP matrix led to increased impact fracture toughness via multiple crazing and crack deviation induced by MWCNT aggregates in the PP matrix, while it had negative effect on the fracture toughness under EWF test condition through hindrance effect on the yielding and necking processes. This contradiction was attributed to the different dominant deformation mechanisms in the PP matrix under high speed multiaxial Izod impact and low speed plane biaxial EWF fracture tests (crazing and shear yielding, respectively). Although the various toughening mechanisms such as nano-bridge mechanism were activated during the fracture processes, vulcanization induced interfacial adhesion improvement between the PP and EPDM particles played the main role in determining of the fracture toughness of the vulcanized blend-nanocomposites.

      PubDate: 2017-07-02T12:08:05Z
       
  • Subtle features of delamination in cross-ply laminates due to low speed
           impact
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Elena Sitnikova, Shuguang Li, Dafei Li, Xiaosu Yi
      In cross-ply laminates, the shape of delamination areas, which form due to low velocity impact, have two subtle features, which have been observed consistently in numerous experiments. Those are the pointed delamination tips and the intact zone between the lobes of delamination. However, there have not been any account available in the literature how they can be consistently captured through numerical modelling, and hence these features in published modelling results were often absent. It is the objective of this paper to identify the underlying modelling considerations so that these features can be captured with confidence. A key and unique reason has been identified in each case. Namely, inclusion of intra-laminar damage allows to reproduce the pointed delamination tips, while the gap between the lobes of delamination can be captured by models with sufficiently refined mesh, where friction between the laminas is taken into account. The capability of capturing these subtle features helps to raise the level of fidelity on the simulation of delamination due to impact.

      PubDate: 2017-07-02T12:08:05Z
       
  • Electromagnetic interference shielding based on a high strength
           polyaniline-aramid nanocomposite
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Jing Lyu, Xing Zhao, Xianliang Hou, Yuchun Zhang, Tiehu Li, Yong Yan
      A composite with hierarchical layering structure characteristics was prepared for electromagnetic interference shielding applications. In this composite, highly conductive polyanilines (PANI) acted as a filler to shield electromagnetic waves and the “strong” aramid nanofibers (ANFs) film played as a matrix material to provide good mechanical property. This composite film with a thickness of several micrometres displayed a shielding effectiveness as high as 30 dB, a mechanical strength of 179 MPa, as well as good stability. These performances combined because the extended PANI molecules which have a very similar molecular structure with aramid molecules “attached” strongly on the surface of aramid nanofibers to form the highly conductive interconnected networks, and the hierarchical layering structure of ANF matrix was reserved. This composite could find potential applications for electromagnetic wave shielding especially when they are coated on curved surfaces and operated with frequent folding and/or stretching.

      PubDate: 2017-07-02T12:08:05Z
       
  • Conductive herringbone structure carbon nanotube/thermoplastic
           polyurethane porous foam tuned by epoxy for high performance flexible
           piezoresistive sensor
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Xiangdong Wei, Xiaohan Cao, Yalong Wang, Guoqiang Zheng, Kun Dai, Chuntai Liu, Changyu Shen
      In this paper, we used epoxy (EP) as a third component to tune the electromechanical performances of the conductive porous foam. A directional ice-template freezing method was utilized to fabricate a carbon nanotubes (CNTs)/EP/thermoplastic polyurethane (TPU) porous foam with a herringbone-like structure. CNTs were homogeneously distributed in the skeleton of the foam. The microstructure of the herringbone-like foam was studied in detail from both the directions perpendicular and parallel to the freezing front movement direction. An ultralow percolation threshold (0.088 vol%) of the conductive foam was achieved. The strength of the CNTs/TPU/EP foam was significantly enhanced with the increase of the CNTs and EP contents. When the foams were exposed to a compression strain from 0 to 70%, the resistance of the porous material decreased in a good linear manner. The foams showed a good differenciation capability towards different compression strain amplitude. Upon multiple cyclic compressive process, the change of the resistance tended to be stable after several compression loading-unloading cycles' measurement. After a pre-compression treatment, the resistance response also became much stable on the basis of the re-arrangement of the conductive network and the stabilized cells structure of the foam. The porous foam possesses a rapid response speed (about 160 ms). Our flexible porous foam with a good chemical resistance can be used in ethanol to sense the finger pressing, and it showed excellent sensing performances when applied to monitor human body motions.

      PubDate: 2017-07-02T12:08:05Z
       
  • Effect of Poly(phthalazinone ether ketone) with amino groups on the
           interfacial performance of carbon fibers reinforced PPBES resin
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Nan Li, Lishuai Zong, Zuoqiang Wu, Cheng Liu, Jinyan Wang, Xigao Jian
      In this study, novel aminated poly(phthalazinone ether ketone) (PPEK-NH2) with amino groups on main chains was synthesized by typical condensation polymerization of 4-(4-Hydroxylphenyl)(2H)-phthalazin-1-one (DHPZ), 4,4’-difluoro benzophenone (DFK), and the third active monomer, 1,5-diamino-4,8-dihydroxyanthraquinon (DDT). As a type of compatibilizer, PPEK-NH2 was utilized to modify the interface properties of carbon fibers (CF) reinforced copoly(phthalazinone ether sulfone)s (PPBES) composites. The composites were prepared by solution impregnation and compression molding, where PPEK-NH2 was distinguished by different mole ratios of DHPZ/DFK/DDT. And the effects of amino structural unit quantity in PPEK-NH2 chains on compatibility was investigated. Of all the compatibilizers, PPEK-NH2 (4) exhibits the best compatible effect. The interlaminar shear strength and flexural strength of CF/PPBES increased significantly by 15.8% and 26.2%, respectively. According to DMA test, the storage modulus and service temperature increase by 12 GPa and 7 °C, respectively. Beside, CF/PPBES/PPEK-NH2 (4) exhibits excellent mechanical behaviours with at 240 °C and 250 °C. Moreover, this composite also demonstrates excellence in hydrothermal aging tests. This method contains simple process, large-scale application potential, which offers new insights for fabricating high-performance advanced thermoplastic composites.

      PubDate: 2017-07-02T12:08:05Z
       
  • Thermal conductivity enhancement of poly(3-hydroxylbutyrate) composites by
           constructing segregated structure with the aid of poly(ethylene oxide)
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Zonglin Li, Junjun Kong, Dandan Ju, Zengwen Cao, Lijing Han, Lisong Dong
      Thermally conductive poly (3-hydroxylbutyrate) (PHB)/poly (ethylene oxide) (PEO)/boron nitride (BN) composites were fabricated by powder mixing. The thermal conductivity of PHB composite was remarkably enhanced by incorporating a small amount of PEO. SEM images revealed that segregated and co-continuous structures were formed in PHB composites. Owing to the addition of PEO, acting as a binder, BN particles were able to stack more closely and covered larger size of PHB aggregates than PHB/BN composites did. In addition, the partial miscibility between PHB and PEO could efficiently improve the interaction between BN particles and PHB matrix. Besides, during the hot pressing process, PEO could penetrate into the voids existing between BN particles and lead the phonon scattering to decrease. The hydrogen bonding existed between PEO and BN particles also played an important role to the thermal conductivity enhancement of PHB composites. These factors combined were believed to result in higher thermal conductivity of PHB/PEO/BN composites than PHB/BN composites fabricated by powder mixing.

      PubDate: 2017-07-02T12:08:05Z
       
  • Rheological characterization of nanostructured material based on
           Polystyrene-b-poly(ethylene-butylene)-b-polystyrene (SEBS) block
           copolymer: Effect of block copolymer composition and nanoparticle geometry
           
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Noushin Hasanabadi, Hossein Nazockdast, Sandor Balog, Marco Lattuada
      Block copolymer (BCP) nanocomposite systems are of broad interest; however, reports on the role of nanoparticles on microphase separation behavior are rare. The goal of present study is to investigate the preparation of composite nanostructured materials containing Multi-Walled Carbon Nanotubes (MWCNTs) or graphene nanoplates. BCP nanocomposites based on the linear triblock copolymer, Polystyrene-b-poly(ethylene-butylene)-b-polystyrene (SEBS), with different morphological structure were prepared by melt mixing. The results of temperature sweep experiments showed an enhancing effect of both MWCNT and graphene nanosheets on increasing the microphase separation temperature as well as accelerating its kinetic, resulting from the confinement of BCP segments, with graphene nanosheets providing a more severely confined geometry for polystyrene segments in contrast to MWCNTs. Additionally, DMTA results indicated a promotion of the BCP microphase separation by incorporation of nanoparticles. Transient flow measurements followed by time sweep test suggested the existence of a special 3D network microstructure caused by nanoparticles/domain interactions.

      PubDate: 2017-07-02T12:08:05Z
       
  • Measurements and predictions of the viscoelastic properties of a composite
           lamina and their sensitivity to temperature and frequency
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): M.V. Pathan, S. Patsias, J.A. Rongong, V.L. Tagarielli
      We perform finite element analysis of the mechanical response of random RVEs representing the microstructure of a unidirectional (UD) fibre composite, predicting its anisotropic stiffness and damping properties and their sensitivity to temperature and frequency, using as inputs only the measured response of the constituents. The simulations are validated by DMTA measurements on a UD composite; then, the numerical predictions are compared to those of previously published theoretical models. New equations are proposed to predict the viscoelastic constants, providing better accuracy than existing models. The accuracy of these new equations is tested, over wide ranges of fibre volume fractions and stiffness ratios of the constituents, against the numerical predictions.

      PubDate: 2017-07-02T12:08:05Z
       
  • Clay/carbon nanotube hybrid mixture to reduce the electrical percolation
           threshold of polymer nanocomposites
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Mohammed H. Al-Saleh
      Creating electrically conductive polymer composites with extremely low nanofiller concentration by melt compounding is a major research challenge. At low nanofiller concentration, the valuable properties of polymers are preserved and the feasibility of the composite is promoted. In this work, an organically modified clay (OMC) was utilized to alter the structure and consequently the electrical resistivity of carbon nanotubes (CNT)/polypropylene (PP) composite. As a result of OMC incorporation, the electrical percolation threshold concentration (EPTC) was reduced from 1.0 wt% CNT for the CNT/PP composite to 0.5 wt% CNT for the CNT:OMC/PP composite, corresponding to 50% reduction in the amount of CNT. The macro-dispersion analysis did not reveal any significant difference between the dispersion of CNT in the CNT/PP and CNT:OMC/PP composites. However, the processing behavior analysis showed a significant decrease in mixing torque and consequently mixing energy due to the addition of OMC. The decrease in mixing torque and/or mixing energy decreases the destruction of CNT aspect ratio. In addition, the DSC analysis showed a decrease in composite crystallinity due to OMC addition. This finding reveals a thinner insulating crystalline layer at the surface of CNT particles and consequently higher electrical conductivity. Based on these experimental findings, it can be speculated that the addition of OMC promoted the conductivity of the composite by decreasing the mixing shear stress and/or polymer crystallinity.

      PubDate: 2017-06-22T01:12:25Z
       
  • A facile method to prepare flexible boron nitride/poly(vinyl alcohol)
           composites with enhanced thermal conductivity
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Jun Zhang, Xiaona Wang, Cuiping Yu, Qiulong Li, Zhuo Li, Chaowei Li, Huifen Lu, Qichong Zhang, Jingxin Zhao, Ming Hu, Yagang Yao
      Polymer infiltrating filler-network has been actively researched recently to obtain composite materials with enhanced thermal conductivities. However, the long infiltration time blocks its wide application. In this study, we prepared hexagonal boron nitride (h-BN)/poly(vinyl alcohol) (PVA) composite by combining polymer infiltration with filler diffusion through the polymer to reduce infiltration time and form heat conduction paths. Base on this process, the maximum thermal conductivities of the obtained h-BN/PVA composites were 1.63 W/m·K and 8.44 W/m·K along the through-plane and in-plane directions, respectively. In addition, the composites displayed excellent heat dissipation performance when attached on top of a light emitting diode (LED) light strip. The research results indicate our approach is facile and capable of fabricating high performance thermal interface materials.

      PubDate: 2017-06-22T01:12:25Z
       
  • Effect of temperature on the electrical property of epoxy composites with
           carbon nanotube
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Shen Gong, Yang Wang, Zhu Xiao, Zhou Li, Zhi X. Wang, Ruo S. Lei, Zheng H. Zhu
      Eliminating the influence of environment temperature is critical for high-accuracy carbon nanotube polymer nanocomposites sensors. In this work, the temperature effects on the nanocomposite are studied by both experiment investigation and simulation calculation. Nearly constant resistance values were found at a CNT loading around 3 wt%. By considering the temperature effect and CNT structural distortion in the developed percolation network model, simulation results agree well with experimental data. On this basis, results show that the thermally assisted tunneling on CNT junctions and thermal expansion of polymer matrix are the two core mechanisms, relaxed CNT junctions in CNT/polymer nanocomposite depressed the temperature effect, and the influence of environment temperature could be significantly reduced by adjusting CNT loadings and choosing a matching polymer matrix. All of these findings will benefit for the design of high-accuracy sensors.

      PubDate: 2017-06-22T01:12:25Z
       
  • Improved mechanical properties of carbon fiber-reinforced epoxy composites
           by growing carbon black on carbon fiber surface
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Jidong Dong, Chuyuan Jia, Mingqiang Wang, Xiaojiao Fang, Huawei Wei, Huaquan Xie, Tong Zhang, Jinmei He, Zaixing Jiang, Yudong Huang
      The interfacial properties between carbon fiber (CF) and matrix play a key role in the mechanical properties of carbon fiber composites. To improve the mechanical properties of fibers/epoxy composites without sacrificing tensile strength of base fibers, carbon black (CB) was introduced onto the surface of CFs by chemical vapour deposition (CVD). The distribution of CBs on the fiber surface and the change of the surface roughness were analyzed, using scanning electron microscopy (SEM) and atomic force microscope (AFM). Raman spectroscopy indicated that the defects of CF surface were repaired by CB. The wettability and surface energy of modified CFs increased obviously in comparison with those of the untreated CFs. Meanwhile, a significant increase of interlaminar shear strength (ILSS), interface shear strength tests (IFSS) and impact property were achieved in the 5-min-modified CFs, which was 22.0, 44.4 and 22.7%, respectively. In addition, the tensile strength (TS) of modified CFs showed a slight increase compared with that of untreated CFs.

      PubDate: 2017-06-22T01:12:25Z
       
  • Mapping fibre failure in situ in carbon fibre reinforced polymers by fast
           synchrotron X-ray computed tomography
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): S.C. Garcea, I. Sinclair, S.M. Spearing, P.J. Withers
      Fast, in situ synchrotron X-ray computed tomography (CT) has been used to capture damage evolution, particularly fibre failures, before final fracture (within 99.9% of the ultimate tensile stress) in cross-ply carbon fibre/epoxy coupons under continuous monotonic tensile loading for the first time. It is noteworthy that fewer than 8% of the fibres in the 0° plies have fractured at 99.9% of the failure load. The majority of fibre breaks appear as isolated events, although some instances of multiple adjacent breaks (clusters) do occur at intermediate and high stress levels. Contrary to conventional wisdom, a cluster of failed fibres always occurred in a burst as a singular failure event: clusters were never seen to accumulate additional broken fibres as load increased suggesting low-level stress concentration local to fibre breaks. Several instances of multiple fractures along individual fibres were observed, providing an estimation of the critical stress transfer length between the fibre and matrix. The factors affecting fibre failure appear to be complex, with distinct sample-to-sample variability being identified for the length-scale tested. This highlights the need for improved understanding of the mechanisms that contribute to final failure, particularly criteria controlling the arrest or otherwise of clustered fracture events.

      PubDate: 2017-06-22T01:12:25Z
       
  • Vitrification during cure produces anomalies and path-dependence in
           electrical resistance of conductive composites
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Geoffrey Rivers, Pearl Lee-Sullivan, Boxin Zhao
      Using a DGEBA/TETA epoxy filled with silver microflakes, we sought to investigate if the onset of conductivity would approximately obey the power-law as cure progresses, as reported in the open literature. We monitored the resistivity change as a function of cure and vitrification behaviour, using a set of concurrent experiments; in-situ four-wire electrical resistance measurements in a newly-developed probe-mold device, and differential scanning calorimetry. It was evident that the electrical conductivity evolved very differently depending on heating conditions, the composite glass transition temperature, and filler content. Periods were observed during cure where electrical conductivity was disrupted, attributed to stresses produced by vitrification. This produced as much as 1500-fold increases in final developed electrical resistance depending on heating conditions and composite glass transition properties, for the same conductive filler content. This discovery has far ranging implications on the industry practice of applying multi-step cure schedules that feature vitrification during cure.

      PubDate: 2017-06-22T01:12:25Z
       
  • Effect of sisal and hydrothermal ageing on the dielectric behaviour of
           polylactide/sisal biocomposites
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): J.D. Badia, P. Reig-Rodrigo, R. Teruel-Juanes, T. Kittikorn, E. Strömberg, M. Ek, S. Karlsson, A. Ribes-Greus
      The dielectric properties of virgin polylactide (PLA) and its reinforced composites with different weight amounts of sisal fibres were assessed at broad temperature (from −130 °C to 130 °C) and frequency ranges (from 10−2–107 Hz), before and after being subjected to accelerated hydrothermal ageing. The synergetic effects of both the loading of sisal and hydrothermal ageing were analysed by means of dielectric relaxation spectra. The relaxation time functions were evaluated by the Havriliak-Negami model, substracting the ohmic contribution of conductivity. The intramolecular and intermolecular relaxations were respectively analysed by means of Arrhenius and Vogel-Fulcher-Tammann-Hesse thermal activation models. The addition of fibre increased the number of hydrogen bonds, which incremented the dielectric permittivity and mainly hindered the non-cooperative relaxations of the biocomposites by increasing the activation energy. Hydrothermal ageing enhanced the formation of the crystalline phase at the so-called transcrystalline region along sisal. This fact hindered the movement of the amorphous PLA fraction, and consequently decreased the dielectric permittivity and increased the dynamic fragility.
      Graphical abstract image

      PubDate: 2017-06-12T01:33:25Z
       
  • Thermally-induced in situ growth of ZnO nanoparticles in polymeric fibrous
           membranes
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Davide Morselli, Paola Valentini, Giovanni Perotto, Alice Scarpellini, Pier Paolo Pompa, Athanassia Athanassiou, Despina Fragouli
      We present a two-step process to obtain PMMA fibrous membranes with homogeneously in situ synthesized zinc oxide nanoparticles of defined shape and size, both on the fibers' surface and bulk. The method is based on the electrospinning of PMMA/precursor solutions and the subsequent thermally activated in situ conversion of zinc acetate to zinc oxide nanoparticles directly in the solid polymeric fibers. X-ray diffraction measurements ensure the formation of crystalline ZnO nanoparticles. Scanning and transmission electron microscopy prove that homogeneously distributed nanoparticles with two different morphologies and size distributions are obtained, depending on the area of the fibers where the nanoparticles are nucleated and on the initial precursor's content. In particular, branched nanoparticles homogeneously decorate the fibers' surface with their dimensions that range from 50 nm to 140 nm for initial precursor contents from 23 to 40 wt%, respectively. On the other hand, small spherical nanoparticles of ca. 7 nm are mainly observed in the bulk of the fibers. Unlike the branched nanoparticles, the dimensions of the spherical nanoparticles are practically unaffected by the precursor amount initially loaded. The homogeneously distributed nanoparticles both on the surface and in the bulk of the polymeric fibers, combined with the high surface area provided by the fibrous structure, result in a multifunctional material characterized by reversible UV-induced wettability and water permeability, improved thermal stability and antibacterial activity particularly promising for diverse applications such as filtration, wound management, photocatalysis, antibacterial and UV-shielding textiles.
      Graphical abstract image

      PubDate: 2017-06-12T01:33:25Z
       
  • In-situ curing of glass fiber reinforced polymer composites via resistive
           heating of carbon nanotube films
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Xiaokui Xu, Yuan Zhang, Jin Jiang, Han Wang, Xinluo Zhao, Qingwen Li, Weibang Lu
      In this study, we report a time- and energy-saving out-of-oven curing process based on the resistive heating of a macroscale carbon nanotube (CNT) film made using the floating catalyst chemical vapor deposition method. CNT film can be heated up very quickly when connected to an electrical power source. By coating CNT film onto the surface of uncured glass fiber reinforced polymer composites, the composites can be cured by the resistive heating of the CNT film. The degree of cure, loss storage, and tensile properties of the composites made from the new process are almost the same as those made from the traditional oven heating process. However, the new curing process is much faster, and its energy consumption is found to be only one seventh that of the oven curing process. The deicing of glass fiber composites based on the resistive heating of CNT film is also demonstrated.

      PubDate: 2017-06-12T01:33:25Z
       
  • Design and characterization for dual-band and multi-band A-sandwich
           composite radome walls
    • Abstract: Publication date: 8 September 2017
      Source:Composites Science and Technology, Volume 149
      Author(s): Licheng Zhou, Peiyu Wang, Yongmao Pei, Anmin Zeng, Liqun Tang, Zejia Liu, Yiping Liu, Zhenyu Jiang, Daining Fang
      Nowadays, radomes that are employed to protect antennas inside from physical environment are required to have dual-band or even multi-band transmission performance. In this paper, a design scheme based on the theory of small reflections is proposed for the design of dual-band and multi-band A-sandwich radomes. Subsequently, two A-sandwich composite radome walls are designed and fabricated according to the design scheme. Finally, both numerical simulations and experiments are conducted to verify the electromagnetic characteristics of the radome walls. Results indicate that one of the A-sandwich radome walls has two passbands in 4.0–11.4 GHz and 25.2–40.0 GHz, while the other one has three passbands in 4.0–8.2 GHz, 18.0–20.5 GHz, and 29.1–40.0 GHz, respectively. The proposed method is experimentally demonstrated to be an effective approach for designing dual-band and multi-band dielectric radome walls for both centimeter and millimeter wave applications.

      PubDate: 2017-06-12T01:33:25Z
       
 
 
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