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ENGINEERING (1225 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: 7)
AASRI Procedia     Open Access   (Followers: 14)
Abstract and Applied Analysis     Open Access   (Followers: 3)
Aceh International Journal of Science and Technology     Open Access   (Followers: 2)
ACS Nano     Full-text available via subscription   (Followers: 271)
Acta Geotechnica     Hybrid Journal   (Followers: 7)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 6)
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: 4)
Advanced Science Letters     Full-text available via subscription   (Followers: 9)
Advanced Science, Engineering and Medicine     Partially Free   (Followers: 7)
Advanced Synthesis & Catalysis     Hybrid Journal   (Followers: 18)
Advances in Calculus of Variations     Hybrid Journal   (Followers: 2)
Advances in Catalysis     Full-text available via subscription   (Followers: 6)
Advances in Complex Systems     Hybrid Journal   (Followers: 7)
Advances in Engineering Software     Hybrid Journal   (Followers: 27)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 16)
Advances in Fuzzy Systems     Open Access   (Followers: 5)
Advances in Geosciences (ADGEO)     Open Access   (Followers: 12)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 22)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 10)
Advances in Natural Sciences: Nanoscience and Nanotechnology     Open Access   (Followers: 30)
Advances in Operations Research     Open Access   (Followers: 12)
Advances in OptoElectronics     Open Access   (Followers: 5)
Advances in Physics Theories and Applications     Open Access   (Followers: 13)
Advances in Polymer Science     Hybrid Journal   (Followers: 43)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Remote Sensing     Open Access   (Followers: 43)
Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Aerobiologia     Hybrid Journal   (Followers: 2)
African Journal of Science, Technology, Innovation and Development     Hybrid Journal   (Followers: 6)
AIChE Journal     Hybrid Journal   (Followers: 32)
Ain Shams Engineering Journal     Open Access   (Followers: 5)
Akademik Platform Mühendislik ve Fen Bilimleri Dergisi     Open Access   (Followers: 1)
Alexandria Engineering Journal     Open Access   (Followers: 1)
AMB Express     Open Access   (Followers: 1)
American Journal of Applied Sciences     Open Access   (Followers: 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: 17)
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: 8)
Annals of Science     Hybrid Journal   (Followers: 7)
Antarctic Science     Hybrid Journal   (Followers: 1)
Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 2)
Applicable Analysis: An International Journal     Hybrid Journal   (Followers: 1)
Applied Catalysis A: General     Hybrid Journal   (Followers: 6)
Applied Catalysis B: Environmental     Hybrid Journal   (Followers: 18)
Applied Clay Science     Hybrid Journal   (Followers: 5)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 12)
Applied Magnetic Resonance     Hybrid Journal   (Followers: 4)
Applied Nanoscience     Open Access   (Followers: 8)
Applied Network Science     Open Access   (Followers: 1)
Applied Numerical Mathematics     Hybrid Journal   (Followers: 5)
Applied Physics Research     Open Access   (Followers: 4)
Applied Sciences     Open Access   (Followers: 3)
Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 5)
Arabian Journal for Science and Engineering     Hybrid Journal   (Followers: 5)
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 5)
Archives of Foundry Engineering     Open Access  
Archives of Thermodynamics     Open Access   (Followers: 8)
Arkiv för Matematik     Hybrid Journal   (Followers: 1)
ASEE Prism     Full-text available via subscription   (Followers: 3)
Asia-Pacific Journal of Science and Technology     Open Access  
Asian Engineering Review     Open Access  
Asian Journal of Applied Science and Engineering     Open Access   (Followers: 1)
Asian Journal of Applied Sciences     Open Access   (Followers: 2)
Asian Journal of Biotechnology     Open Access   (Followers: 8)
Asian Journal of Control     Hybrid Journal  
Asian Journal of Current Engineering & Maths     Open Access  
Asian Journal of Technology Innovation     Hybrid Journal   (Followers: 8)
Assembly Automation     Hybrid Journal   (Followers: 2)
at - Automatisierungstechnik     Hybrid Journal   (Followers: 1)
ATZagenda     Hybrid Journal  
ATZextra worldwide     Hybrid Journal  
Australasian Physical & Engineering Sciences in Medicine     Hybrid Journal   (Followers: 1)
Australian Journal of Multi-Disciplinary Engineering     Full-text available via subscription   (Followers: 2)
Autonomous Mental Development, IEEE Transactions on     Hybrid Journal   (Followers: 9)
Avances en Ciencias e Ingeniería     Open Access  
Balkan Region Conference on Engineering and Business Education     Open Access   (Followers: 1)
Bangladesh Journal of Scientific and Industrial Research     Open Access  
Basin Research     Hybrid Journal   (Followers: 5)
Batteries     Open Access   (Followers: 6)
Bautechnik     Hybrid Journal   (Followers: 1)
Bell Labs Technical Journal     Hybrid Journal   (Followers: 26)
Beni-Suef University Journal of Basic and Applied Sciences     Open Access   (Followers: 4)
BER : Manufacturing Survey : Full Survey     Full-text available via subscription   (Followers: 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: 4)
Bharatiya Vaigyanik evam Audyogik Anusandhan Patrika (BVAAP)     Open Access   (Followers: 1)
Biofuels Engineering     Open Access   (Followers: 1)
Biointerphases     Open Access   (Followers: 1)
Biomaterials Science     Full-text available via subscription   (Followers: 11)
Biomedical Engineering     Hybrid Journal   (Followers: 15)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 14)
Biomedical Engineering Letters     Hybrid Journal   (Followers: 5)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 18)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 34)
Biomedical Engineering: Applications, Basis and Communications     Hybrid Journal   (Followers: 5)
Biomedical Microdevices     Hybrid Journal   (Followers: 9)
Biomedical Science and Engineering     Open Access   (Followers: 4)
Biomedizinische Technik - Biomedical Engineering     Hybrid Journal  
Biomicrofluidics     Open Access   (Followers: 4)
BioNanoMaterials     Hybrid Journal   (Followers: 2)
Biotechnology Progress     Hybrid Journal   (Followers: 39)
Boletin Cientifico Tecnico INIMET     Open Access  
Botswana Journal of Technology     Full-text available via subscription   (Followers: 1)
Boundary Value Problems     Open Access   (Followers: 1)
Brazilian Journal of Science and Technology     Open Access   (Followers: 2)
Broadcasting, IEEE Transactions on     Hybrid Journal   (Followers: 10)
Bulletin of Canadian Petroleum Geology     Full-text available via subscription   (Followers: 14)
Bulletin of Engineering Geology and the Environment     Hybrid Journal   (Followers: 14)
Bulletin of the Crimean Astrophysical Observatory     Hybrid Journal  
Cahiers, Droit, Sciences et Technologies     Open Access  
Calphad     Hybrid Journal  
Canadian Geotechnical Journal     Hybrid Journal   (Followers: 30)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 44)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 7)
Case Studies in Thermal Engineering     Open Access   (Followers: 5)
Catalysis Communications     Hybrid Journal   (Followers: 6)
Catalysis Letters     Hybrid Journal   (Followers: 2)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 8)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysis Today     Hybrid Journal   (Followers: 7)
CEAS Space Journal     Hybrid Journal   (Followers: 2)
Cellular and Molecular Neurobiology     Hybrid Journal   (Followers: 3)
Central European Journal of Engineering     Hybrid Journal   (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: 24)
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: 4)
Cogent Engineering     Open Access   (Followers: 2)
Cognitive Computation     Hybrid Journal   (Followers: 4)
Color Research & Application     Hybrid Journal   (Followers: 2)
COMBINATORICA     Hybrid Journal  
Combustion Theory and Modelling     Hybrid Journal   (Followers: 14)
Combustion, Explosion, and Shock Waves     Hybrid Journal   (Followers: 13)
Communications Engineer     Hybrid Journal   (Followers: 1)
Communications in Numerical Methods in Engineering     Hybrid Journal   (Followers: 2)
Components, Packaging and Manufacturing Technology, IEEE Transactions on     Hybrid Journal   (Followers: 28)
Composite Interfaces     Hybrid Journal   (Followers: 7)
Composite Structures     Hybrid Journal   (Followers: 280)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 206)
Composites Part B : Engineering     Hybrid Journal   (Followers: 259)
Composites Science and Technology     Hybrid Journal   (Followers: 200)
Comptes Rendus Mécanique     Full-text available via subscription   (Followers: 2)
Computation     Open Access  
Computational Geosciences     Hybrid Journal   (Followers: 15)
Computational Optimization and Applications     Hybrid Journal   (Followers: 7)
Computational Science and Discovery     Full-text available via subscription   (Followers: 2)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 8)
Computer Science and Engineering     Open Access   (Followers: 19)
Computers & Geosciences     Hybrid Journal   (Followers: 30)
Computers & Mathematics with Applications     Full-text available via subscription   (Followers: 7)
Computers and Electronics in Agriculture     Hybrid Journal   (Followers: 5)
Computers and Geotechnics     Hybrid Journal   (Followers: 11)
Computing and Visualization in Science     Hybrid Journal   (Followers: 6)
Computing in Science & Engineering     Full-text available via subscription   (Followers: 33)
Conciencia Tecnologica     Open Access  
Concurrent Engineering     Hybrid Journal   (Followers: 3)
Continuum Mechanics and Thermodynamics     Hybrid Journal   (Followers: 8)
Control and Dynamic Systems     Full-text available via subscription   (Followers: 9)
Control Engineering Practice     Hybrid Journal   (Followers: 43)
Control Theory and Informatics     Open Access   (Followers: 8)
Corrosion Science     Hybrid Journal   (Followers: 25)
Corrosion Series     Full-text available via subscription   (Followers: 6)
CT&F Ciencia, Tecnologia y Futuro     Open Access   (Followers: 1)

        1 2 3 4 5 6 7 | Last

Journal Cover Composites Science and Technology
  [SJR: 1.512]   [H-I: 144]   [200 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0266-3538
   Published by Elsevier Homepage  [3177 journals]
  • Recyclable and superelastic aerogels based on carbon nanotubes and
           carboxymethyl cellulose
    • Abstract: Publication date: 3 May 2018
      Source:Composites Science and Technology, Volume 159
      Author(s): Alireza Hajian, Qiliang Fu, Lars A. Berglund
      Deformation mechanisms are largely unknown for superelastic carbon nanotube (CNT) aerogels, and this hampers materials design efforts. The CNT network in the cell walls is typically crosslinked or connected by a thermoset polymer phase. In order to create a recyclable superelastic aerogel, unmodified single or multi-walled CNTs were dispersed in water by adding to aqueous carboxymethyl cellulose (CMC) solution. Directional freeze-drying was used to form honeycombs with cell walls of random-in-the-plane CNTs in CMC matrix. Cell wall morphology and porosity were studied and related to CNT type and content, as well as elastic or plastic buckling of the cell walls under deformation. CMC acts as a physical crosslinker for the CNTs in a porous cell wall. Aerogel structure and properties were characterized before and after recycling. The conductivity of the composite aerogel with a density of 10 kg/m3, 99% porosity and 50 wt % single-walled CNT exceeds 0.5 S/cm. The potential of these superelastic and conductive aerogels for applications such as mechanoresponsive materials was examined in cyclic conductivity tests at different strains. This opens a new route for recyclable superelastic CNT composite aerogels, avoiding material loss, chemical treatment or addition of other components.
      Graphical abstract image

      PubDate: 2018-02-26T01:48:26Z
  • Biodegradable silica rubber core-shell nanoparticles and their
           stereocomplex for efficient PLA toughening
    • Abstract: Publication date: 3 May 2018
      Source:Composites Science and Technology, Volume 159
      Author(s): Zibiao Li, Joseph K. Muiruri, Warintorn Thitsartarn, Xing Zhang, Beng Hoon Tan, Chaobin He
      In the effort to overcome the shortcomings such as brittleness and poor mechanical stability, and increase the competitive edge of renewable poly(lactic acid) PLA over conventional petroleum-based thermoplastics, silica rubber core-shell nanoparticles for effective PLA toughening were successfully synthesized by sequential ring opening polymerization (ROP). The core-shell structure was designed with silica as inner core, P(CL-mLA) as ‘rubber’ middle layer and terminal PDLA chains (SiO2-r-PDLA), to facilitate the stereocomplex formation with PLLA matrix for enhanced interface control. The PLLA/SiO2-r-PDLA nanocomposites were fabricated through solution blending-injection molding process. Nuclear magnetic resonance (1H NMR and 13C NMR) results confirmed the presence of grafted ’rubber’ and PDLA chains from the surface of silica particle. In addition, PLLA/SiO2-r-PDLA nanocomposites showed tremendous improvement in thermal and mechanical properties using differential scanning calorimetry (DSC) and tensile testing, respectively. Besides the formation of stereocomplex in the nanocomposites, a detailed study on the melt stability of these stereocomplex nanocomposites revealed a ‘memorized’ stereocomplex behavior, i.e., having the ability to perfectly reassemble after re-crystallization from melt (melt memory effect), when rubber segment is present. Finally, structure-deformation mechanisms were studied using scanning electron microscopy (SEM) and small angle x-ray scattering (SAXS). From SAXS, crazing was clearly observed whereas SEM revealed fibrillated structures. Thus, crazing and fibrillation are the key deformation mechanisms in PLLA/SiO2-r-PDLA system. The exciting new fillers could open up new horizons for PLA advanced composites applications.
      Graphical abstract image

      PubDate: 2018-02-26T01:48:26Z
  • Investigation of strain history in fast and conventional curing epoxy
           matrix composites by FBGs
    • Abstract: Publication date: 3 May 2018
      Source:Composites Science and Technology, Volume 159
      Author(s): Yixin Qi, Dazhi Jiang, Su Ju, Jianwei Zhang
      A comprehensive understanding of strain history in resin matrix composite, which is caused by variability of thermo-mechanical properties of the resin during composite processing, is essential to allow better design and control of properties of the resin matrix composite. In this paper, to know strain history of fast curing epoxy matrix composite and differences of strain history between fast and conventional curing epoxy matrix composites well, temperature and strain history at different locations in ten-ply unidirectional carbon-fiber fabrics reinforced the fast and conventional curing epoxy matrix composite laminates manufactured by wet lay-up method were measured by fiber Bragg grating (FBG) sensors. Results shown that the peak temperature due to curing exothermal reaction was 133.7 °C in both the 1st ply and the 5th ply in the fast curing composite when cure temperature profile settled at 80 °C, which was 27.4 °C higher than that in the conventional curing composite. Cure residual strain in the 1st ply and the 5th ply in the fast curing composite were −5183.3 με and −4074.7 με, respectively; while they were −2975.9 με and −2660.8 με in the conventional curing composite. The related properties of rheology and cure kinetics of the epoxy resin were thus given in advance.

      PubDate: 2018-02-26T01:48:26Z
  • Transparent and flexible high frequency transmission lines based on
           composite structure comprising silver nanowires and polyvinyl butyral
    • Abstract: Publication date: 3 May 2018
      Source:Composites Science and Technology, Volume 159
      Author(s): Sang-Woo Kim, Kwangho Kim, Wansoo Nah, Cheul-Ro Lee, Seung-Boo Jung, Jong-Woong Kim
      Percolated networks of silver nanowires (AgNWs) have attracted intensive attention because of their remarkable mechanical stability, along with their excellent optical and electrical performance for the fabrication of flexible transparent electrodes. Most prior research has mainly focused on fabricating transparent electrodes that can be used in optoelectronic devices such as touch sensors, light emitting diodes, and photovoltaics. However, fabrication of transparent and flexible transmission lines designed to conduct alternating current of high frequency has not been reported so far. Herein, we developed highly transparent, mechanically stable transmission line by employing inverted layer processing (ILP) in order to embed the AgNWs just below the surface of a free-standing transparent polymer. For this, we synthesized polyvinyl butyral (PVB), which can be prepared from polyvinyl alcohol by reaction with butyraldehyde, for AgNW support. AgNWs deposited on a preliminary substrate (glass) were plasmonically sintered to significantly enhance their conductivity, and then transferred to the surface of the cured PVB film by the ILP. Measurements and simulation of specially designed coplanar waveguide circuits comprising AgNWs and PVB revealed that the fabricated electrode can simultaneously provide impressive transmission performance as well as excellent mechanical flexibility and transparency. An interesting finding was that the transmission characteristics and mechanical stability are in a trade-off relationship, which needs to be carefully considered in the design and selection of materials for the flexible transmission lines.

      PubDate: 2018-02-26T01:48:26Z
  • Effect of annealing treatment on crystalline and dielectric properties of
           PVDF/PEG-containing ionic liquid composites
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Pei Xu, Weijia Fu, Yadong Hu, Yunsheng Ding
      To investigate the effect of poly(ethylene glycol)-containing ionic liquid (IL) and thermal annealing treatment on crystallization and dielectric relaxation behavior of poly(vinylidene fluoride) (PVDF), a series of PVDF/IL composites have been prepared using a solution-cast method. The interaction between imidazolium cation of ILs and >CF2 groups of PVDF can transfer nonpolar α phase to polar β and γ phase as a template at the primary crystallization, and then the interaction between PEG of ILs and >CF2 groups of PVDF can facilitate the PVDF chains in amorphous region to bring more polar phase and decrease the degree of crystallization for PVDF composites according to the template under thermal annealing treatment. The experimental dielectric data were analyzed within the formalisms of complex permittivity and electric modulus. In the frequency spectra of PVDF composites, dc conductivity, electrode and Maxwell-Wagner-Sillars (MWS) interfacial polarization resulted in high values of dielectric permittivity. The incorporation of ILs into the matrix and thermal annealing treatment can accelerate dc conductivity. The temperature dependence of relaxation time of dc conductivity follows the Arrhenius equation. The effect of annealing treatment on charge carrier movement mechanism was resulted from the increase of ion mobility induced by polymer chain segmental motion and polar phase crystals.

      PubDate: 2018-02-26T01:48:26Z
  • In situ assembly of SiO2 nanodots/layered double hydroxide nanocomposite
           for the reinforcement of solution-polymerized butadiene styrene
           rubber/butadiene rubber
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Linghan Kong, Feng Li, Fanghui Wang, Ye Miao, Xidai Huang, Hong Zhu, Yonglai Lu
      In the present work, SiO2 nanodots were in situ assembled with MgAl-layered double hydroxide (LDH), and the resulting SiO2/LDH nanocomposite was mixed and vulcanized with solution-polymerized styrene butadiene rubber/butadiene rubber (SSBR/BR) to form rubber composites (SiO2/LDH-SSBR/BR). The structure of SiO2/LDH and the resulting rubber composites were characterized by SEM, TEM, high-resolution TEM, XRD, FT-IR, and XPS. It was found that SiO2 nanodots were uniformly dispersed on the surface of LDH, and that the SiO2/LDH was highly compounded with SSBR/BR. With the increasing content of SiO2/LDH, the elongation at break of the SSBR/BR composites increased as much as 600%, while the tensile strength increased gradually and exceeded that of the commercial Zeosil 1165 MP highly-dispersed nano-SiO2 (Zeosil 1165 MP). These results demonstrate the high reinforcing effect of SiO2/LDH-SSBR/BR elastomer composites. Compared with that of Zeosil 1165 MP-SSBR/BR, the tan δ of as-formed SiO2/LDH-SSBR/BR is 48% higher at 0 °C, but 62% lower at 60 °C. Meanwhile, the present SiO2/LDH-SSBR/BR possesses high wet skid resistance and low rolling resistance, and the heat build-up decreases 6.1 °C compared with Zeosil 1165 MP, which provide a promising potential for high-performance green tire applications.

      PubDate: 2018-02-26T01:48:26Z
  • Carbon fiber assisted glass fabric composite materials for broadband radar
           cross section reduction
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Yongqiang Pang, Yongfeng Li, Jiafu Wang, Mingbao Yan, Hongya Chen, Liangkui Sun, Zhuo Xu, Shaobo Qu
      Carbon fibers (CFs) have been widely used as absorbing materials for radar cross section (RCS) reduction. Here, an alternative approach for CFs is proposed to achieve the same goal and has been performed by the glass fabric composites loaded with a small number of CFs. The reduction mechanism of our proposal is phase cancellation instead of absorption. Two prototypes in chessboard and random patterns are analyzed numerically and measured experimentally. The short CF yarns are designed as the patterned configurations and embedded into the composite surface layers. It is demonstrated that the proposed composites allow for remarkable suppressing of the specular scattering over a broad frequency band. The designed RCS reduction level more than 10 dB covers the frequency range from 8.7 to 19.2 GHz, while the overall thickness is 2.7 mm. The proposed composites are of a simple configuration and robust for the defects. It is also believed that the study of this work can be easily extended to the curved surfaces.

      PubDate: 2018-02-26T01:48:26Z
  • Strong and biocompatible lignin /poly (3-hydroxybutyrate) composite
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Dan Kai, Hui Moon Chong, Li Ping Chow, Lu Jiang, Qianyu Lin, Kangyi Zhang, Huijie Zhang, Zheng Zhang, Xian Jun Loh
      Poly(3-hydroxybutyrate) (PHB) is an attractive biopolymer potential for various applications, but its brittle nature is a big handicap. In this study, we proposed lignin copolymers as mechanical reinforcement agents for PHB. A series of lignin copolymers (random and block) were synthesized via the solvent free ring-opening polymerization (ROP) of β-butyrolactone and/or ε-caprolactone onto lignin core. The lignin copolymers were characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). Next, these lignin copolymers were incorporated into PHB nanofibers as reinforcement fillers, in order to improve their mechanical properties. It is found that the lignin block copolymer with poly(ε-caprolactone) (PCL) segment followed by PHB segment (LPC + H) displayed the best mechanical improvement. Tensile strength of PHB nanofibers enhanced from 1.81 MPa to 3.13 MPa, and elongation at break increased from 15% of 55%. In the reinforced system, lignin plays as a rigid core, PCL acts a rubbery layer and PHB segment forms strong bonding with fiber matrix. Moreover, PHB/lignin nanofibers were demonstrated with superior biodegradability and biocompatibility, indicating that the new nanofibrous system holds great potential for biomedical applications.
      Graphical abstract image

      PubDate: 2018-02-26T01:48:26Z
  • Sustainable packaging biocomposites from polylactic acid and wheat straw:
           Enhanced physical performance by solid state shear milling process
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Shuangqiao Yang, Shibing Bai, Qi Wang
      As a sustainable and inexpensive agricultural byproduct, wheat straw has gained major interest as filler in green composites in recent years, but previous studies about PLA/wheat straw composites have reported modest enhancement or even major reduction in physical performance. Here, we report a new method for both production cellulose nanofibrils and achieving excellent dispersion in composites free of solvent for the first time, and enhanced physical performance is obtained via solid state shear milling process (SSSM). The SSSM pretreatment process led wheat straw an ultrafine particle size and even the separation of cellulose nanofibrils from micro-sized pristine cellulose fibers. Both optical and electron microscopy revealed that composites made by SSSM process exhibit excellent dispersion of hemicellulose, lignin and cellulose nanofibrils which derived from wheat straw. Such PLA/wheat straw composites exhibited fast crystallization rate with 0.8 min crystallization half-time and 41.4% crystallinity, leading major enhancement in flexural modulus which exceed the known value reported in the literature. In addition, a heat deflection temperature of 73 °C is observed with 30%wt wheat straw, which is much higher than neat PLA. Furthermore, high water vapor permeability is observed in composites, enabling food packaging applications especially for respiring fresh products such as fruits and vegetable. The approach presented in this paper highlights a novel technique for recovering wheat straw in producing value-added products.

      PubDate: 2018-02-26T01:48:26Z
  • Fabrication and properties of novel polymer-metal composites using fused
           deposition modeling
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Matthew A. Ryder, Diana A. Lados, Germano S. Iannacchione, Amy M. Peterson
      This study investigated the novel fabrication of polymer-metal composites using fused deposition modeling (FDM), and evaluated the mechanical and physical properties of the new materials. Specifically, an acrylonitrile butadiene styrene (ABS) – 420 stainless steel (SS) composite system was used, with 10, 15, and 23 wt% SS powder additions, and the resulting properties were compared to those of base ABS prepared using the same printing conditions. A new methodology to fabricate the composites was developed. The resulting materials were extruded into composite filaments, which were used to print test specimens. Tensile testing, modulated differential scanning calorimetry, and scanning electron microscopy were employed to characterize the composite materials and evaluate the effects of different print conditions. The results demonstrate, for the first time, the feasibility of using FDM to prepare ABS-SS composites that maintain or enhance mechanical properties as compared to the base polymer, while adding increased functionality.

      PubDate: 2018-02-26T01:48:26Z
  • Fabrication of an enriched graphene surface protection of carbon
           fiber/epoxy composites for lightning strike via a percolating-assisted
           resin film infusion method
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Ben Wang, Yugang Duan, Zhibo Xin, Xueling Yao, Dilmurat Abliz, Gerhard Ziegmann
      A low-conductivity feature of carbon fiber-reinforced polymers (CFRP) needs to be engineered with lightning strike protection to decrease the vulnerability of the material to lightning strike damage. This paper reports a percolating-assisted resin film infusion method that achieves a conductive lightning strike protection via the accumulation of reduced graphene oxide (RGO) on the composite surface. In this method, the fibrous preform was sealed by the filter paper and the sealant tape to form a confined region that avoids the expansion of RGO from the fibrous preform while also limiting the RGO flow along the thickness direction, and thus RGO accumulates on the CFRP surface through filtration mechanisms. The enriched RGO on CFRP allowed high conductivity values (440 S/cm vs. 16 S/cm of CFRP) on the surface while also improving the thermal resistance of CFRP. As a result, RGO protection dramatically improved the lightning damage resistance as compared to CFRP. The residual strength, characterized via 3-point flexural testing after a simulated lightning test, only decreased by 23% as compared to its initial value, whereas a drastic reduction (66%) was observed for pristine CFRP.

      PubDate: 2018-02-26T01:48:26Z
  • Dynamic and regional constructive electromagnetic protecting materials
           made by MWNT/Fe3O4/poly pyrrole doped vitrimers
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Hong Zhang, Haiping Han, Xuecheng Xu
      Electromagnetic protection is always an important factor for electrical device. Therefore electromagnetic shielding materials (ESM) with good properties such and easy-processing is desirable. Vitrimer, a kind of material that equipped with advantages of both thermoplastics and thermosets, such as proof of acid and alkaline, mechanical stability, and easy processing was recently discovered. In our research, we use vitrimer as matrix, doped with MWNT/Fe3O4 composite, to form a new kind of ESM. MWNT/Fe3O4 was prepared by MWNT and Fe(acac)3. Outcome has shown that such ESM is stable at room temperature and suitably deformable at evaluated temperature, making it easy for constructing surface fitted ESM. Also, MWNT absorption of light focus enables its spatial and regional deformation. Fe(acac)3 prepared MWNT/Fe3O4 showed a significant improvement in microwave-range reflection loss. Lap-shear test provided almost an equal capacity of self-healing under external force and magnetic force. As a result, the ESM showed promising perspective on wilder usage of electromagnetic protection with greater properties.

      PubDate: 2018-02-26T01:48:26Z
  • Effect of vacuum thermal cycling on the compression and shear performance
           of composite sandwich structures containing pyramidal truss cores
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Xiaodong Li, Jian Xiong, Li Ma, Linzhi Wu, Xiangqiao Yan
      Composite pyramidal-truss core sandwich panels, in which the lattice core is strengthened by reinforced frames between dispersive nodes, were manufactured via water-jet cutting and interlocking assembly. The coefficients of thermal expansion and outgassing (mass loss) ratios of the composite laminates were determined. Subsequently, the effect of vacuum thermal cycling on the compression and shear performance of the composite sandwich panels with pyramidal-truss cores was studied using theoretical and experimental methods. In particular, the out-of-plane compression stiffness and strength, as well as the shear stiffness and strength of the structures subjected to vacuum thermal cycling, were predicted using theoretical equations. The compression and shear performance improved initially and then deteriorated with an increase in the vacuum thermal cycling-time. The observed failure modes depended on the number of vacuum thermal cycles. In addition, the catastrophic response of the composite sandwich panels with pyramidal-truss cores was investigated, and their possible failure modes (including the crushing and localized buckling of composite struts) were complemented with results of analytical modeling. The truss cores collapsed mainly due to crushing and localized-buckling processes, caused by matrix outgassing and debonding of the interface between the carbon fibers and epoxy resin, after prolonged thermal cycling.

      PubDate: 2018-02-26T01:48:26Z
  • Novel three-component nanocomposites with high dielectric permittivity and
           low dielectric loss co-filled by carboxyl-functionalized multi-walled
           nanotube and BaTiO3
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Shanshan Guan, Hai Li, Shugao Zhao, Laina Guo
      In this work, a novel ternary polydimethylsiloxane (PDMS)-based nanocomposite co-filled by carboxyl-functionalized multi-walled nanotube (cMWCNT) and BaTiO3(BT) nanoparticle were developed. The hybrids cMWCNT-BT was realized via the hydrogen bonding (H-bonding) interaction between –COOH groups of cMWCNT and the -OH groups of BT. Compared with the binary composite of BT/PDMS and cMWCNT/PDMS, the results showed that the kind of three-component nanocomposites had high dielectric permittivity and low dielectric loss. Different from cMWCNT, the hybrids cMWCNT-BT have good dispersion in PDMS matrix, forming many micro-capacitors and interfaces, and thus leading to remarkably high dielectric constant. Meanwhile, BT on the surfaces of cMWCNT reduce the direct contact of cMWCNT, resulting in reduced dielectric loss. More important, the BT and cMWCNT had a synergistic effect on dielectric permittivity of the cMWCNT-BT/PDMS composite. Therefore, the dielectric properties of the novel ternary composite can be improved by optimizing the synergistic effects between the charge storage behavior of the ferroelectric phase and the charge transport behavior of the conductive phase.

      PubDate: 2018-02-26T01:48:26Z
  • Porous superhydrophobic polymer/carbon composites for lightweight and
           self-cleaning EMI shielding application
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Xiaohui Ma, Bin Shen, Lihua Zhang, Yinfeng Liu, Wentao Zhai, Wenge Zheng
      Porous superhydrophobic polymer composites with satisfying electromagnetic interference (EMI) shielding and self-cleaning function were fabricated by choosing poly(vinylidene fluoride) as low-surface-energy matrix as well as carbon nanotubes and graphene as hybrid filler through a modified water vapor-induced phase separation process with non-woven fabric (NWF) as a template in one step. The hybrid filler can form more effective conductive networks, and the NWF template combined with hybrid filler and porous microstructure composed of assemble spherulites can roughen the composites, creating multi-scaled raspy surface. The resultant material exhibited not only large water contact angle of 155.4° ± 2.7° (in accord with superhydrophobic characteristic) and excellent EMI shielding effectiveness up to ∼28.5 dB at only thickness of ∼2 mm, but also good performance stability under ultraviolet (UV) irradiation. This simple and reproducible technique together with UV-resistant superhydrophobicity and EMI shielding would facilitate practical application of such materials.

      PubDate: 2018-02-26T01:48:26Z
  • Strain sensing behaviors of GnPs/epoxy sensor and health monitoring for
           composite materials under monotonic tensile and cyclic deformation
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Shaowei Lu, Caijiao Tian, Xiaoqiang Wang, Lu Zhang, Kai Du, Keming Ma, Tao Xu
      The graphene platelets (GnPs)/epoxy flexible sensor with controllable sensitivity and linearity can be used to monitor the deformation and damage of composite structures. The sensitivity and linearity can be regulated by dispersing different content of GnPs in epoxy and the dispersion was better improved by optimizing ultrasonic time and the ball mill mixing process. The GnPs/epoxy mixture exhibited relatively low percolation threshold of 0.76 vol %. In this paper, GnPs/epoxy mixtures with GnPs loading of 0.84 vol.%, 1.05 vol % and 1.58 vol % were selected as damage detecting and strain sensor, and the characteristics of sensors were demonstrated via various mechanical tests. The monotonic tensile results suggest that there are three different linear change sensing stages, (1–0.2%), (0.2%–0.6%) and (0.6%–1.2%), the linear growth of the electrical response is softened while the linear tendency is enhanced due to increasing GnPs content, and it exhibits relatively high gauge factor of 11.81, 15.25 and 22.54 for 0.84 vol %, 3.63, 8.13, 11.46 for 1.05 vol % and 2.53, 3.77, 4.69 for 1.58 vol % in different sensing stages respectively. The sensor of 0.84 vol % is more reversibility than 1.05 vol % upon cyclic loading-unloading test. The GnPs/epoxy sensor show promising applications for the damage monitoring of structural composite in the field of aerospace.

      PubDate: 2018-02-26T01:48:26Z
  • Multifunctional epoxy/carbon fiber laminates for thermal energy storage
           and release
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Giulia Fredi, Andrea Dorigato, Luca Fambri, Alessandro Pegoretti
      This work is focused on the preparation and characterization of novel multifunctional structural composites with thermal energy storage (TES) capability. Structural laminates were obtained by combining an epoxy resin, a paraffinic phase change material (PCM) stabilized with carbon nanotubes (CNTs), and reinforcing carbon fibers. The stabilized paraffin kept its ability to melt and crystallize in the laminates, and the melting enthalpy of the composites was proportional to the paraffin weight fraction with a maximum value of 47.4 J/cm3. This thermal response was preserved even after fifty consecutive heating-cooling cycles. Moreover, the thermal conductivity of the laminates through thickness direction resulted to increase proportionally to the content of CNT-stabilized PCM. The capability of the developed TES laminates to contribute to the thermal energy management was also proven by monitoring their cooling rates through thermal imaging. The flexural modulus was only slightly affected by the presence of the PCM, while a decrease of flexural strength, strain at break and interlaminar shear strength was detected. Optical microscopy highlighted that this could be attributed to the preferential location of the PCM in the interlaminar region. The obtained results demonstrated the feasibility of the concept of multifunctional structural TES composites.

      PubDate: 2018-02-26T01:48:26Z
  • Enhanced dielectric tunability and energy storage properties of plate-like
           Ba0.6Sr0.4TiO3/poly(vinylidene fluoride) composites through texture
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Li Wang, Feng Gao, Jie Xu, Kena Zhang, Jie Kong, Mike Reece, Haixue Yan
      Plate-like (Ba0.6Sr0.4)TiO3 (P-BST) particles were synthesized via topochemical microcrystal conversion using a two-step molten salt method. In addition, P-BST/poly(vinylidene fluoride) (PVDF) textured composites were fabricated using a tape casting and hot pressing method. The influence of the P-BST particle size on the microstructure, dielectric tunability, and energy storage properties of the P-BST/PVDF textured composites was investigated. The results revealed that P-BST/PVDF textured composites can be obtained with preferred orientation of plate-like particles, which exhibit uniform directionality in the PVDF matrix. The dielectric properties of these composites increased with increasing P-BST particle size. A new criterion EP 80 was proposed for evaluating the dielectric tunability of composites. The optimal properties of the P-BST/PVDF textured composite (minimum threshold electric field: 14 kV/mm, minimum EP 80: 29 kV/mm, and maximum energy storage density: 6.36 J/cm3) were realized at a P-BST particle size of 11.47 μm. A dielectric tunability model for inorganic/organic composites with respect to the shape factor (n) of the inorganic fillers was proposed and used to simulate the dielectric tunability of the textured composites. For the P-BST/PVDF composite, n of 4–5 in the model corresponded to P-BST particle sizes of 5.19 μm–11.47 μm.

      PubDate: 2018-02-26T01:48:26Z
  • Helical flow-driven alignment of off-axial silver-functionalized titanium
           dioxide fibers in polypropylene tube suitable for medical applications
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Kailin Zhang, Xiao Li, Min Nie, Qi Wang
      Inspired by Bouligand-type structure in natural materials featured with helically-aligned reinforcing fibers and superior kink-resistance, we demonstrated an analogous architectural configuration in polypropylene (PP) tube by mean of manipulating helical flow and Ag-coated titanium dioxide (TiO2) fibers. Firstly, the dopamine-assisted immobilization and in situ reduction of Ag ions were completed on the surface of TiO2 fiber, endowing the latter with antibacterial property. Then, the functionalized fibers were introduced into PP matrix, and extruded longitudinally, simultaneously with mandrel rotation, constructing a unique helical flow. Preferred orientation driven by the applied flow assembled the bioinspired Bouligand-like structure with helically-aligned functionalized TiO2 fibers, benefiting torque load bearing and thereby the bulk kink-resistance of polymer tube accompanied by high antibacterial activity. This was exemplified by a substantial increase of 40% in hoop strength with large bacterial inhibition zone in comparison with the pure PP counterpart prepared via convention extrusion. This Bouligand-mimetic alignment strategy can open up a promising possibility of engineering and develop a series of reinforced architectures via simple industrial melt process, satisfying special functionalities and applications unavailable with the other processing technologies.

      PubDate: 2018-02-26T01:48:26Z
  • Multi-functional hydroxyapatite/polyvinyl alcohol composite aerogels with
           self-cleaning, superior fire resistance and low thermal conductivity
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Wenwen Guo, Jiajia Liu, Ping Zhang, Lei Song, Xin Wang, Yuan Hu
      Hybrid inorganic/polymer composite aerogels combine the advantages of both components which can overcome the brittle fracture of inorganic aerogels as well as high flammability of polymeric aerogels. Herein, we reported a facile approach to prepare polyvinyl alcohol (PVA)-hydroxyapatite (HAP) composite aerogel by freeze-casting process towards multi-functional aerogel materials. The incorporation of HAPs led to significant reduction in the peak heat release rate (−79%), total heat release (−76%), specific extinction area (−65%) and CO production (−45%). Vertical burning tests also manifested that PVA-HAP composite aerogels displayed excellent fire resistance and self-extinguishing behaviours. The resultant PVA-HAP composite aerogels also showed a low thermal conductivity (33.6–38.7 mW m−1 K−1). The hydrogen bonding formed between the HAP and the PVA matrix endowed the resultant composite aerogels with a specific modulus (58.7 kN m−1 kg−1) which was comparable to or even higher than those reported by state-of-the-art foams, including polystyrene foams, polyurethane foams and silica aerogels. After a facile polydimethylsiloxane treatment, the resultant PVA-HAP composite aerogels also exhibited water-repellent and self-cleaning capacity, which is a promising candidate as building insulating materials.

      PubDate: 2018-02-26T01:48:26Z
  • Achieving high-performance poly (styrene-b-ethylene-ranbutylene-b-styrene)
           nanocomposites with tannic acid functionalized graphene oxide
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Jianfeng Wang, Xiuxiu Jin, Xiaomeng Zhang, Lichao Xia, Chunhai Li, Hong Wu, Shaoyun Guo
      In this paper, graphene oxide (GO) was functionalized with tannic acid (TA), an easy-available and low-cost plant, on the GO surface through simple ultrasound-/shearing-assisted solution blending. The TA endows GO a stronger interfacial interaction with poly (styrene-b-ethylene-ran-butylene-b-styrene) (SEBS) and greatly improves the dispersion of GO in the SEBS, resulting in a much high efficiency of GO on improving the performance of the matrix. By adding 10 wt % of TA-GO (weight ratio of TA and GO = 2:1), the dielectric constant of SEBS matrix at 100 Hz reached up to 58.7, about 27-fold and 7-fold increment compared with that of neat SEBS and SEBS/GO nanocomposites, respectively. Moreover, compared with neat SEBS, the tensile strength, modulus and fracture toughness of SEBS/TA-GO nanocomposites with the addition of 0.5 wt% of TA-GO were enhanced by 122%, 91% and 107%, respectively. GO-induced firbous SEBS and microcrack formed around GO were found and proposed as the toughening and reinforcing mechanism of TA-GO in SEBS. This study not only provides a strategy to prepare high-performance SEBS nanocomposites, but also puts forward a facile, easy, low-cost and effective strategy to enhance the graphene-polymer interfacial interaction and improve the dispersion of graphene in the polymers.

      PubDate: 2018-02-26T01:48:26Z
  • Ultralow electrical percolation in melt-compounded polymer composites
           based on chemically expanded graphite
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Peng Wang, Haodan Chong, Jiajia Zhang, Yanhao Yang, Hongbin Lu
      It has been difficult to construct electrical percolation networks in melt-compounded polymer composites due to shear-induced network destruction, especially for low graphene content composites. To overcome this issue, here we employ chemically expanded graphite (CEG) to construct conductive networks in which the polymer molecules would penetrate into the inner part of CEG to form a polymer entrapped in CEG structure. This novel polymer entrapped in CEG structure is very useful for the effective charge transfer and further construction of conductive networks in the process of melt compounding. The final polymer composites exhibit an ultralow electrical conductive percolation threshold of 0.29 vol% after melt compounding which is almost among the lowest level compared with those of other melt-compounded polymer composites. Besides, the thermal conductivity of the composites is also significantly enhanced. This strategy here has provided a new way to maintain the conductive networks and decrease the electrical percolation threshold in the melt-compounded polymer composites through constructing polymer entrapped in conductive fillers structure.

      PubDate: 2018-02-26T01:48:26Z
  • Elastomer nanocomposites with superior dynamic mechanical properties via
           trans-1, 4-poly (butadiene-co-isoprene) incorporation
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Xinping Zhang, Honghong Cui, Liyuan Song, Huicheng Ren, Riguo Wang, Aihua He
      A new strategy for high performance tire tread stocks is proposed by incorporating novel synthetic crystalline trans-1, 4-poly (butadiene-co-isoprene) rubber (TBIR) into the traditional amorphous SSBR/BR blends. The silica filled SSBR/BR/TBIR composites after chemical crosslinking exhibited significantly improved dynamical properties compared with filled SSBR/BR composites, such as 2–3 times higher tensile fatigue resistance, improved wet-skid resistance and abrasion resistance, lower rolling resistance and heat built-up, etc. Further discussions revealed that crystalline TBIR components improved silica dispersion by increasing the strength and modulus of SSBR/BR/TBIR rubber matrix, and modulated network structures of the rubber matrix in the form of TBIR lamellar fibrils, both of which were expected to contribute to the greatly improved tensile fatigue resistance and other properties. The incorporation of TBIR in tire tread stocks will provide a solution for high performance tire production without changing the present processing technology and formulations.
      Graphical abstract image

      PubDate: 2018-02-26T01:48:26Z
  • High electromechanical performance of modified electrostrictive
           polyurethane three-phase composites
    • Abstract: Publication date: 12 April 2018
      Source:Composites Science and Technology, Volume 158
      Author(s): Ardimas, Chatchai Putson, Nantakan Muensit
      In order to enhance the electrostrictive polymer, the polyurethane has been modified with conductive fillers that are promising for actuator applications, energy conversion, and sensors. The polyurethane (PU) matrix and the conductive fillers such as graphene nanosheets (GRN) and polyaniline nanopowder (PANI) were prepared to gain films by solution casting method. The morphology, structure and thermal behavior of PU three-phase composite were observed by SEM imaging, FTIR, and DSC techniques. In addition, the electrical and mechanical properties of polyurethane filled with both composites were investigated by an LCR meter and strain gauge setup. In order to study the electrostriction behavior, the electric field induced strain of PU three-phase composite films was monitored via lock-in amplifier at a low frequency of 1 Hz. A greater electrostriction effect of the PU three-phase composites at low electric field significantly related with contribute to conduction and interfacial polarization base on space charges distribution, filler-filler network and microstructure on crystallinity in the HS domain of PU matrix. Therefore, electrostriction behavior in the PU three-phase composites has been discussion. It was known that why the three-phase composites can provide high electromechanical performance for actuator applications.

      PubDate: 2018-02-26T01:48:26Z
  • One-step modification and nanofibrillation of microfibrillated cellulose
           for simultaneously reinforcing and toughening of poly(ε-caprolactone)
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Sha Deng, Jinrui Ma, Yilan Guo, Feng Chen, Qiang Fu
      Extensive efforts have been devoted to utilize cellulose fibers as reinforcement for poly(ε-caprolactone) (PCL) to prepare fully biodegradable composites with enhanced mechanical properties, but unfortunately the improvement of strength is always at the sacrifice of toughness. In the current work, we have developed an efficient way to prepare poly(ε-caprolactone)/functionalized cellulose nanofibers (PCL/f-NFC) nanocomposite, which is both strong and ductile. Large scale f-NFC was produced from microfibrillated cellulose (MFC) in one step through the synergy of mechanical and chemical actions derived from ball milling. The f-NFC with nanosized scale and tailored hydrophobicity is compatible with PCL, which leads to strong interfacial interaction between f-NFC and PCL and good dispersion of f-NFC in PCL. The tensile strength of this bionanocomposite undergoes a remarkable enhancement nearly 100% and elongation-at-break increases by 68% with extremely low f-NFC content as 0.1 wt%. Since both surface property and fiber size affect the performance of composites, original MFC, functionalized MFC (f-MFC) and cellulose nanofibers (NFC) without hydrophobic modification are also incorporated into PCL to make a systematic comparative study to identify the dominating factor influencing the performance. The overall results suggest that surface modification plays a dominant role at low fiber content, while nano-sized scale is much more beneficial at high fiber content. Most importantly, the synergistic effect of surface modification and nano-sized scale leads to significantly improved tensile properties across a wide range of fiber content.

      PubDate: 2018-02-26T01:48:26Z
  • A novel mild method for surface treatment of carbon fibres in epoxy-matrix
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Nikos Koutroumanis, Anastasios C. Manikas, Panagiotis Nektarios Pappas, Faidonas Petropoulos, Lamprini Sygellou, Dimitrios Tasis, Kostas Papagelis, George Anagnostopoulos, Costas Galiotis
      The interface quality between the reinforcement and the host matrix plays a key role in the mechanical performance of Carbon Fibre/Epoxy Resin (CFRP) composites. In most cases, an adequately strong interfacial bond is induced chemically either by the oxidation of the carbon fibre (CF) surface and/or by means of mechanical interlocking (friction). Here, a mild chemical process involving CF's functionalization via an epoxidation reaction at room temperature (RT) is being proposed. By immersing the CF in an organic solution (chloroperoxybenzoic acid in dichloromethane), the outer surface is functionalized with oxygen moieties, such as epoxy rings, at optimized grafting densities. The room-temperature method described here is more advantageous that other oxidative treatments since it is cost-effective, environmentally friendly and does not damage the fibre surface. Furthermore, as detected by Laser Raman microscopy a considerable 2.3-fold increase of the maximum interfacial shear stress was observed for the treated CF/Epoxy systems as compared to the pristine-untreated-samples.

      PubDate: 2018-02-26T01:48:26Z
  • In-situ synthesized CNTs/Bi2Se3 nanocomposites by a facile wet chemical
           method and its application for enhancing fire safety of epoxy resin
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Yanbei Hou, Weizhao Hu, Longxiang Liu, Zhou Gui, Yuan Hu
      In this work, a flowering-branch like CNTs/Bi2Se3 hybrids was synthesized by a facile in-situ method. CNTs as carrier could provide low agglomeration of layered Bi2Se3. As-prepared nanomaterials were added into epoxy resin (EP) to enhance its fire safety. Compared with neat EP, there were more than 44% and 23% decrease in the value of peak heat release and total heat release with 2 wt% content of CNTs/Bi2Se3, respectively, confirmed the enhancement of flame retardancy of EP composites. Meanwhile, the release of smoke and CO were also suppressed during EP combustion. From results of thermogravimetric analysis-infrared spectrometry, the addition of CNTs/Bi2Se3 obviously reduced the release of organic gaseous products, which contributed to the improved fire safety of EP matrix. Based on the analysis of gas and condensed phases, the possible enhancement mechanisms can be mainly concluded as the barrier effect of as-synthesized binary hybrids and enhanced char layers. Meanwhile, the addition of CNTs/Bi2Se3 enhanced the mechanical performance of EP composites. This work broadens the application fields of Bi2Se3 and enriches the membership of CNTs-based binary compounds, which were used as flame retardants.
      Graphical abstract image

      PubDate: 2018-02-26T01:48:26Z
  • A cohesive zone model incorporating a Coulomb friction law for
           fiber-reinforced composites
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Guodong Nian, Qiyang Li, Qiang Xu, Shaoxing Qu
      A cohesive zone model (CZM) combining interfacial debonding, frictional sliding, and coupling between decohesion and friction is developed. The proposed interface model forms by incorporating a Coulomb friction law into the bilinear traction-separation law, and only one additional parameter is introduced compared to the traditional CZM. To verify this model, microbond test is carried out using an in-house developed tester. The interface model has been implemented into a commercial software package ABAQUS as a user-defined element. An axisymmetric finite element model with geometry and boundary conditions identical to the physical test has been used to simulate interfacial debonding and frictional sliding. The parameters for the interface model are determined by comparing the results of experiment and simulation. Once the parameters have been obtained for one test, the interface model can be used without further modification to predict the results of other experiments. The present interface model gives excellent quantitative predictions for the results of microbond test. Moreover, dimensional analysis has been adopted to study the relationship between the interfacial behavior and various parameters including the interfacial properties and the geometry of the structure. Dimensional considerations introduce a characteristic length, and the interfacial shear strength (IFSS) monotonically increases with the ratio of the characteristic length to the embedded length and is asymptotic to a horizontal line.

      PubDate: 2018-02-26T01:48:26Z
  • Reinforcement of shape-memory poly(ethylene-co-vinyl acetate) by carbon
           fibre to access robust recovery capability under resistant condition
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Hui Xie, Lu Li, Xiao-Ying Deng, Chuan-Ying Cheng, Ke-Ke Yang, Yu-Zhong Wang
      Poly (ethylene-co-vinyl acetate) (EVA), as one of commercial polymers, has been used early to fabricate shape-memory polymers (SMPs). However, its low recovery stress restricts the potential applications in some tough conditions due to its high flexible feature. Herein, we developed a series of EVA-based composites (cEVA/CF) with remarkably enhanced recovery stress both in free-state and resistant condition by incorporating different amounts of a stiff filler carbon fibre (CF) into the commercial EVA matrix. The observation of morphology showed that CF was well dispersed in EVA matrix, and the thermal properties of cEVA/CF composites were just slightly affected as demonstrated by the DSC analysis. More importantly, the modulus of composites was significantly improved, especially above the melting temperature (T m). This feature is valuable to improve the recovery stress of cEVA/CF composites as both the shape deformation and recovery occur at T > T m. To investigate the recovery behaviors of the cEVA/CF composites in free-state or with varying external loads, the strategy that combing appropriate clamp operation and well-designed procedures under two DMA modes (DMA Controlled Force and DMA Iso-Strain) was put forward. Compared with pristine cEVA, cEVA/CF composites with 5–30 wt% CF possessed 100–650% increase of recovery stress. Consequently, cEVA/CF composites exhibited a robust shape recovery performance under resistant condition, while the recovery capability of pristine cEVA was totally depressed. Aiming at practical applications, a model of deployable device made of cEVA/CF30 was well-established.
      Graphical abstract image

      PubDate: 2018-02-26T01:48:26Z
  • Formation of the three-dimensional (3D) interlinked hybrid shish-kebabs in
           injection-molded PE/PE-g-CNF composite by “structuring” processing
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Xiao-Chao Xia, Dan-Dan Xie, Yan-Hao Huang, Ming-Bo Yang
      The target of this study is to construct 3D interlinked structure that mimicks the structure of shell by “structuring” processing. Therefore, lightly cross-linked HDPE and PE-g-CNF that aligned along the flow direction by intense shear flow were purposely designed. During this process, strong interfacial ligaments were built on the surface of ordered CNFs. At the same time, innumerable linked kababs were formed, and they served as bridges to tightly link adjacent hybrid shish-kebab structures. The 3D interlinked structure endowed composites with unprecedented mechanical properties. Specifically, compared with PE and R-PE samples, the yield strength increased by 137.7% and 79.0%, and Young's modulus enhanced by 160.6% and 109.6%. What's more, the 3D interlinked structure overcame the brittle fracture of composites. In this light, the proposed method is promising to widen the application of structural bionics in industrial manufacture.
      Graphical abstract image

      PubDate: 2018-02-26T01:48:26Z
  • Effect of cell morphology on electrical properties and electromagnetic
           interference shielding of graphene-poly(methyl methacrylate) microcellular
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Seyed Esmaeil Zakiyan, Hamed Azizi, Ismaeil Ghasemi
      Nowadays, polymer-based foams have gained much attention for absorption of electromagnetic wave due to their desirable properties such as wide absorption band, low reflection and also light weight. However, the impact of the foam morphology including shape, cell size and its structure as open and close cell, on the electromagnetic wave has been rarely investigated. In this study, the operational conditions for manufacturing various structured foams based on poly(methyl methacrylate)/graphene nanoparticle sheets have been optimized for investigating the effect of cellular structure on the characteristics of electromagnetic wave as well as electrical properties. Hence, a foaming system with great controllability and repeatability has been employed. It should be noted that this system is capable of stabilizing the cellular structure with millisecond accuracy during and after the pressure drop. The close cell structured foam showed a decrement in the electrical and electromagnetic properties with increasing the cell size and shifting from spherical to polygonal shape. Moreover, the results related to the prepared open cell structured foams with similar cell size and density to close cell ones, have demonstrated higher absorption characteristics for microcellular open cell foams while shielding was better in close cell counterparts.

      PubDate: 2018-02-26T01:48:26Z
  • Thermoelectric and mechanical properties of PLA/Bi0·5Sb1·5Te3 composite
           wires used for 3D printing
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Jizhe Wang, Hongze Li, Rongxuan Liu, Liangliang Li, Yuan-Hua Lin, Ce-Wen Nan
      Thermoelectric (TE) composite wires with polylactic acid (PLA) as the matrix and Bi0·5Sb1·5Te3 (BST) as the filler are synthesized by extruding. The effects of silane coupling agent KH570, plasticizer ATBC, and conductive additive multi-walled carbon nanotubes (MWCNTs) on the composition, TE, and mechanical properties of the composite wires are systematically studied. It is necessary to add KH570 into the composite wires to make the actual BST loading the same as the designed value. The addition of ATBC greatly increases the flexibility of the composite wires and improves the wires' mechanical properties. When the BST loading increases from 35.8 to 87.5 wt%, the flexural modulus increases from 1684.0 to 4379.8 MPa and the flexural strength monotonically decreases from 50.1 to 13.4 MPa. In aspect of TE properties, the power factor PF of the composite wires increases with the increase of the BST loading, and the maximum Seebeck coefficient reaches 200 μV K−1. When MWCNTs are added into the composite wires, the electrical conductivity is significantly enhanced and thus the PF of the wires is raised. The highest PF of 11.3 μW m−1 K−2 is obtained for the wire containing 81.3 wt% BST and 4 wt% MWCNTs. A TE figure of merit ZT of 0.011 is obtained at room temperature. The excellent TE properties and satisfactory mechanical properties of the BST/PLA composite wires make them a promising candidate used for 3D printing of TE devices.

      PubDate: 2018-02-05T00:48:06Z
  • A novel expandable porous composite based on acetalized polyvinyl alcohol
           and calcium sulfate used for injectable bone repair materials
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Hongyu Du, Yudong Zheng, Wei He, Yi Sun, Yansen Wang
      Calcium sulfate hemihydrate (CaSO4·1/2H2O; CSH) has been used for filling bone defects because of its excellent biocompatibility and injectability. Researchers have devoted in improving its performance to adapt to various demands. However, up to now, no studies have reported bone cement with expandable ability. In this study, a novel expandable bone cement was prepared with acetalized polyvinyl alchol porous material (APVA-PM) and CSH. By controlling the content of APAV-PM, composite cements with different structures and morphology were obtained and investigated by using SEM, FT-IR, XRD. The physical properties including setting time, porosity and expansion ratio were studied. CSH/APVA-PM bone cement could produce volume expansion in the setting process and form a porous structure after curing. The setting time decreased with the increase of the volume fraction of APVA-PM. APVA-PM improved the toughness of calcium sulfate cement, thus overcoming the present mechanical limitations. In vitro experiments demonstrated the CSH/APVA-PM bone cement did not show cytotoxicity and the porous structure allowed the rat bone marrow stem cells (BMSCs) to grow into the pores. Therefore, CSH/APVA-PM bone cement appeared to be useful for bone tissue engineering and can potentially serve as a new filling material.
      Graphical abstract image

      PubDate: 2018-02-05T00:48:06Z
  • Highly enhanced electromechanical properties of PVDF-TrFE/SWCNT
           nanocomposites using an efficient polymer compatibilizer
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Kie Yong Cho, Hyunchul Park, Hyun-Ji Kim, Xuan Huy Do, Chong Min Koo, Seung Sang Hwang, Ho Gyu Yoon, Kyung-Youl Baek
      PVDF-TrFE/SWCNT nanocomposites with outstanding electromechanical properties were produced using P3HT-PMMA block copolymers as a compatibilizer between PVDF-TrFE and SWCNT. P3HT-PMMA block copolymer coated SWCNT (PTMCNT) was first prepared to utilize π-π stacking interactions between SWCNT and the P3HT block segment. The obtained PTMCNTs are highly compatible with the PVDF-TrFE matrix due to strong hydrogen bonding interaction between the polymer matrix and the PMMA block segment on the surface of SWCNT, leading to a very low percolation behavior at 0.05 wt% of SWCNT in PVDF-TrFE. The obtained electroactive PVDF-TrFE/SWCNT nanocomposites showed ca. 50 times increased electromechanical thickness strain, ca. 3200 times increased elastic energy density, and ca. 460 times increased electrical-to-mechanical energy conversion rate in comparison to those of pristine PVDF-TrFE at the relatively low electric field (50 Vppμm-1). These outstanding properties result from the ultra-low percolation of SWCNT along with uniform local field distribution in PVDF-TrFE, which kept not only intrinsic properties of PVDF-TrFE such as all-trans formed crystalline phase and softness but also enhanced electrical properties including dielectric constant.
      Graphical abstract image

      PubDate: 2018-02-05T00:48:06Z
  • CNT-PAN hybrid nanofibrous mat interleaved carbon/epoxy laminates with
           improved Mode I interlaminar fracture toughness
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Volkan Eskizeybek, Adem Yar, Ahmet Avcı
      Interleaving laminated composites with electrospun nanofibrous mats comes out as a promising micro--scale strategy to strengthen interlaminar regions of laminated composites. The aim of this study is to evaluate the synergetic contribution of nano- and micro-scale mechanisms on interlaminar delamination. For this, carbon nanotubes (CNTs) reinforced polyacrylonitrile (PAN) electrospun hybrid mats were successfully fabricated and utilized as interleaves within the interlaminar region of carbon/epoxy laminated composites. The Mode I interlaminar fracture toughness values were enhanced up to 77% by introducing CNTPAN nanofibrous interleaves. Specifically, the nano-scale toughening mechanisms such as CNTs bridging, CNTs pull-out, and sword-sheath increased the Mode I fracture toughness by 45% with respect to neat PAN nanofibrous interleaves. The related micro- and nano-scale toughening mechanisms were evaluated based on the fracture surface analysis. Atomic force microscopy was also utilized to quantify the magnitude of surface roughness changes on the interlaminar region with respect to multi-scale interleaving reinforcement and correlate surface roughness changes due to crack deflection to increased fracture toughness.

      PubDate: 2018-02-05T00:48:06Z
  • Hot-pressing composite curling deformation characteristics of plastic
           film-reinforced pliable decorative sliced veneer
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Xiaorui Peng, Zhankuan Zhang
      The new type of plastic-film-reinforced pliable decorative sliced veneer (PRPDSV) is a green product that features remarkable water resistance, no glue penetration, easy operation, low cost, good environmental protection, and no formaldehyde release. However, curling deformation under high-temperature hot-pressing is a bottleneck in the industrial development of this product. The relationship among hot-pressing temperature, thickness of decorative sliced veneer and plastic film, and type of decorative sliced veneer and curling deformation was studied through calculating experimental and theoretical models to explore the factors that influence the curling deformation of PRPDSV under hot-pressing. The nonlinear finite element analysis method was used for the first time to establish the elastic-plastic finite element simulation model of the PRPDSV composite. A comparison of the results obtained through the job visualization model and the experimental results indicated the reliability of the established model. Results showed that the hot-pressing temperature had a remarkable effect on the curling deformation of PRPDSV. As the hot-pressing temperature increased, the curvature radius of the curling deformation decreased and the curling degree gradually increased. The curling deformation was small when the ratio of the thickness of decorative sliced veneer was greater than that of the plastic film. The decorative sliced veneer with dense wood pores and other cellular tissues presented slight curling deformation from the hot-pressing composite.

      PubDate: 2018-02-05T00:48:06Z
  • Enhancement of dielectric constant in polymer-ceramic nanocomposite for
           flexible electronics and energy storage applications
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Sunil Kumar, Sweety Supriya, Manoranjan Kar
      The polymer nanocomposites have potential applications in flexible electronics due to its interesting dielectric properties. Hence, flexible nanocomposite films of polyvinylidene fluoride (PVDF) polymer and barium hexaferrite (BHF) nanoparticles with high dielectric constant were prepared by the solution cast method. The dielectric behavior of the materials has been understood by employing the impedance spectroscopy technique. The co-existence of α and β phases of PVDF has been observed from the XRD (X-ray Diffractometer) and FTIR (Fourier-transform infrared spectroscopy) analysis. The ratio of α and β phases of PVDF has a great influence on dielectric, ferroelectric and energy storage density of PVDF-BHF nanocomposites and, it depends upon the concentration of BHF in the nanocomposites. FE-SEM (Field Emission Scanning Electron Microscopy) micrographs reveal that the microstructure of the composite depends upon the concentration of BHF in the PVDF matrix. Dielectric properties of nanocomposite highly depends on microstructure of the PVDF-BHF nanocomposite. This observation has been well explained by considering the BLCs (Barrier Layer capacitances) model. Interestingly, the dielectric constant has been enhanced eighteen (18) times at 1 KHz to that of dielectric constant of PVDF. The dielectric constant increases due to the electrostatics and interfacial interaction between the local electric field of the BHF nanoparticle and CH2/CF2 dipole of PVDF chain. The present study opens a new window for the possible use of PVDF-BHF nanocomposite in dielectric and energy storage device applications.

      PubDate: 2018-02-05T00:48:06Z
  • Enhanced sheet-sheet welding and interfacial wettability of 3D graphene
           networks as radiation protection in gamma-irradiated epoxy composites
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Haibo Wang, Nan Li, Zhiwei Xu, Xu Tian, Wei Mai, Jing Li, Cheng Chen, Lei Chen, Hongjun Fu, Xingxiang Zhang
      3D graphene networks (3DGN) as reinforcement for epoxy composites have attracted intense attention, while the interfacial adhesion with the matrix is still a key issue. With respect to the impact between interfacial wettability for graphene sheets in 3DGN and the performance for epoxy-based composites, 3DGNs prepared by self-assembly method, have been carbonized in N2 at heat treatment temperature between 220 and 800 °C, and then incorporated into epoxy by resin transfer molding method. Polyving akohol serving as cross-linking agent is converted to amorphous carbon during the annealing process, which effectively interconnects and enhances graphene sheet-sheet welding. When the carbonization temperature is 400 °C (3DGN-4), epoxy contact angles decrease from 100.2° to 56.7°, and 3DGN-4/epoxy composites are increased significantly 84% and 56% in compressive and flexural strength, respectively. In the meantime, this 3DGN serving as radiation protection of epoxy composites has been investigated for the first time. The electron spin resonance detection shows that 3DGN could act as radical scavenger in the gamma irradiation environment, and mechanical performance retention rate of 3DGN-4/epoxy composites is above 92% after gamma irradiation, which is higher than that of epoxy resin. Therefore, the designed 3D graphene networks can be considered as promising candidates for improving both the mechanical properties and radiation resistance of epoxy composites.

      PubDate: 2018-02-05T00:48:06Z
  • Terahertz time-domain spectroscopy of weld line defects formed during an
           injection moulding process
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Gyung-Hwan Oh, Ji-Hye Jeong, Sung-Hyeon Park, Hak-Sung Kim
      The terahertz time-domain spectroscopy (THz-TDS) imaging technique was used to detect the weld line defect of an injection-moulded short glass fiber-reinforced composite. To determine the effect of the weld lines on tensile strength, tensile tests were conducted with the specimens fabricated with NORYL (amorphous blends of polyphenylene ether resin and polystyrene) having a short glass fiber content ranging from 0% to 30%. The time delay phenomenon of the THz waves was observed with respect to the weld line and short glass fiber contents. The interaction between the THz waves and structural characteristics of the weld line, such as density and fiber orientation, were studied and different time delay phenomena of THz signal were observed owing to the different refractive index of the weld line defect. The refractive index of THz wave was also obtained by an analytical calculation and compared with the experimental results in order to determine the correlation between degradations of tensile strength and changes in the reflected THz wave caused by the weld line. Finally, the weld line defect of the specimens was successfully detected and identified using a THz-TDS imaging technique, showing that this technique is a nondestructive inspection method that can be utilized to evaluate the reliability of injection moulded short glass fiber-reinforced composite structures.

      PubDate: 2018-02-05T00:48:06Z
  • Homogeneous transfer of graphene oxide into photoresist: Fabrication of
           high surface area three-dimensional micro-arrays by modified
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Bing Xue, Yingquan Zou
      Herein, we studied the homogeneous transfer of graphene oxide (GO) into photocurable SU-8 photoresist for fabricating GO/SU-8 three-dimensional (3D) composite micropillar arrays by modified photolithography. SU-8 is a negative toned epoxy based photoresist, which includes 8 epoxy groups in each SU-8 monomer. The effects of the concentration of GO flakes on the thermal, mechanical and specific surface area (SSA) properties of the resultant composites were investigated. The large amount of oxygen functional groups on the GO plane and at the edges allowed uniform distribution of GO sheets within the SU-8 resin. The GO/SU-8 micropillar arrays were fabricated by a versatile ultraviolet (UV) photolithography technique that allowed the synthesis of various 3D micro–nano integrated carbon microelectrode arrays. The integrated GO flakes were bonded to the surface or embedded within the primary structure of SU-8 micro-pillars. These SU-8 micropillars having surface-bonded or embedded GO flakes showed superior thermal stability, strength, and SSA characteristics than bare SU-8 micropillars. Thus, this new synthesis approach provides a novel route for developing high performance catalysts, sensors, and adsorbents, among other materials.

      PubDate: 2018-02-05T00:48:06Z
  • A coupled elastic-plastic damage model for the mechanical behavior of
           three-dimensional (3D) braided composites
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Jingran Ge, Chunwang He, Jun Liang, Yanfei Chen, Daining Fang
      A coupled elastic-plastic damage model is developed to describe the non-linear mechanical behavior of three-dimensional (3D) braided composites. In this model, the fiber breakage, inter-fiber fracture and matrix fracture are considered in the level of the fiber bundle and matrix. The onset and propagation of fiber bundle failure mechanisms are elastic and brittle, which is accounted for elastic damage model, and the elastic-plastic damage model used to describe the degradation of matrix is non-linear with progressive damage and inelastic strains. A set of internal variables are introduced to characterize the damage states of the fiber bundle and matrix and as a subsequence the degradation of the material stiffness. The damage initiation and propagation criteria are based on the Hashin criteria for the fiber bundle and the von Mises yield criterion for the matrix. The proposed damage model is implemented in the non-linear finite element analysis code ABAQUS using a user-subroutine UMAT to determine the response behavior of 3D braided composites under quasi-static loading, and the numerical predictions are compared with experimental data. The results predicted by the proposed model agree well with the experiment.

      PubDate: 2018-02-05T00:48:06Z
  • Failure mechanisms in bioinspired helicoidal laminates
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): J.L. Liu, H.P. Lee, V.B.C. Tan
      Previous research has shown that stacking unidirectional laminates helicoidally with small interply angles resulted in improvements in transverse load resistance. Guided by computational simulations, damage evolution within helicoidal and cross-ply laminates was tracked with further experiments to offer an insight into key differences responsible for their distinct load bearing characteristics. Under transverse loads, the first form of damage is delamination. Unlike cross-plys, which suffer multiple delamination of about the same size throughout the thickness, delamination is harder to initiate in helicoidal laminates due to the small angle between each ply. A large delamination eventually formed at the mid-plane. Transverse cracks then appear on the tensile surface of both types of specimens and propagate upwards with increasing loads. Load drops occur whenever the transverse cracks propagate to the delamination immediately above them. In the case of cross-plys, where there are multiple delamination, multiple load drops occur. Load drops in helicoidal laminates are delayed until the cracks reach the large delamination in the mid-plane. Helicoidal specimens do not experience multiple loads drops and can attain high peak load before catastrophic failure. It is shown that even higher peak load is achieved by selectively seeding delamination in helicoidal laminates to further delay the merging of transverse cracks with the dominant delamination.

      PubDate: 2018-02-05T00:48:06Z
  • A flexible transparent heater with ultrahigh thermal efficiency and fast
           thermal response speed based on a simple solution-processed indium tin
           oxide nanoparticles-silver nanowires composite structure on
           photo-polymeric film
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Chaewon Kim, Mi Jung Lee, Sung-Jei Hong, Young-Sung Kim, Jae-Yong Lee
      In this study, a composite structure consisting of indium tin oxide nanoparticles (ITO-NPs)-silver nanowires (Ag NWs) on photo-polymeric film was intensively studied for flexible transparent heater with ultrahigh thermal efficiency and fast thermal response speed. For cost-effective manufacturing, a simple solution process was employed to make low-cost composite structure by using 0.15 wt% Ag NWs and 5 wt% ITO-NPs solution. Among 3 types, namely, 2-layer (Ag NWs/ITO-NPs), 2′-layer (ITO-NPs/Ag NWs), and 3-layer (ITO-NPs/Ag NWs/ITO-NPs) sample, the composite structure was optimized as 3-layer, which raised temperature by more than 15% compared to the 1-layer sample (Ag NWs only) at the same voltage. In addition, the 3-layer sample made on Norland optical adhesive 63 (NOA 63) photo-polymeric film exhibited good characteristics as a flexible transparent heater. Optical transmittance at 550 nm (T550) of the 3-layer sample was 89.92%, which was similar to that of the 1-layer sample (90.87%). However, sheet resistance (Rs) of the 3-layer sample was 19.56 Ω/sq., which was remarkably lower than that of the 1-layer sample, 78.45 Ω/sq. In addition, an ultrahigh thermal efficiency (328 °C/(W/cm2)) was achieved from the 3-layer composite structure on the NOA 63 film. Thermal response speed of the 3-layer sample was as ultrafast as 10 s and temperature within 90 °C and 100 °C stably increased and decreased during 60 cycles when applying 5 V. Moreover, the 3-layer sample stably generated heat even under the extreme bending diameter of 5 mm, and heat-generating properties, such as thermal response speed, saturated temperature, and cooling rate, remained almost unchanged even after bending for 1000 cycles.

      PubDate: 2018-02-05T00:48:06Z
  • Polyphenylene sulfide nonwoven-based composite separator with superior
           heat-resistance and flame retardancy for high power lithium ion battery
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Dan Luo, Meng Chen, Jing Xu, Xianze Yin, Jing Wu, Shaohua Chen, Luoxin Wang, Hua Wang
      In this study, a new alternative nonwoven based on engineering plastic polyphenylene sulfide (PPS) was explored as the support to construct high performance and safety separator for the first time. By the method of physical coating polymer poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) and inorganic nanoparticle SiO2 on the support, the designed composite separator was successfully obtained for lithium ion battery. Systematic investigations ranging from physical properties, thermal properties to electrochemical performances were carried out. It was found that compared with commercialized polyolefin separator, PPS nonwoven-based composite separator possessed higher porosity, air permeability, improved electrolyte wettability and electrolyte uptake, thus being helpful for lithium ion transfer between electrodes and increasing the ionic conductivity. These behaviors accordingly endowed battery with superior discharge capacity at various discharge current rates from 0.2 C to 2 C. Moreover, the composite separator was observed to exhibit excellent dimensional stability even after thermal treatment at 250 °C and present good flame retardant ability. The afore-mentioned outstanding performances of PPS nonwoven-based composite separator would shed light on the development of high power lithium ion battery.

      PubDate: 2018-02-05T00:48:06Z
  • Flexural deformation and fracture behaviors of bamboo with gradient
           hierarchical fibrous structure and water content
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Guowei Chen, Hongyun Luo, Sujun Wu, Juan Guan, Jun Luo, Tianshu Zhao
      Natural gradient fibrous bamboo bended from two opposite directions (divided as Type I and Type II samples) showed pronounced asymmetric flexural performances as the water contents gradually increased (0%, 6%, 22% and 35%). The real-time flexural deformation and fracture behaviors were detected and analyzed with the aid of acoustic emission (AE). Results indicated that there were three kinds of mechanical behaviors during the flexural deformation and fracture process of bamboo: matrix (parenchyma cells) failure, fiber interfacial dissociations (fiber/matrix and fiber/fiber wall dissociations) and fiber breakage. They showed different sequences within the Type I and Type II samples, which were caused by the gradient fibrous structure. The AE energy was dramatically declined and the fiber interfacial dissociations showed exponential-like growth as the water content increased. Upon certain content of water, the gradient hierarchical fibrous structures were toughened through detailed mechanisms of micro-fiber pull-out, debonding and bridging, laminar debonding, local cell wall buckling and micro wart swelling. The study provides critical experimental evidences on the effects of gradient fibrous structure and water content on the flexural performance and fracture behaviors of the natural bamboo.

      PubDate: 2018-02-05T00:48:06Z
  • Towards balanced mechanical and electrical properties of thermoplastic
           vulcanizates composites via unique synergistic effects of single-walled
           carbon nanotubes and graphene
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Chao-Qun Li, Jun-Wei Zha, Zhi-Jun Li, Dong-Li Zhang, Si-Jiao Wang, Zhi-Min Dang
      To achieve good dispersion of graphene and single-walled carbon nanotubes (SWNTs) in the nonpolar thermoplastic vulcanizate (TPV), polypropylene-graft-maleic anhydride (PP-g-MA) was compounded with graphene or SWNTs to obtain masterbatches, followed by their melt blending with TPV material. Morphological observations revealed the rather different distribution of graphene and SWNTs, which was directly related to the form of unique dual conductivity networks via the incorporation of SWNTs and graphene hybrid fillers, and also prevented the aggregation of fillers efficiently. The TPV ternary composites incorporated with hybrid fillers of graphene and SWNTs exhibited a low electrical percolation threshold of 0.37 wt % SWNTs, and higher electrical and thermal conductivity than the SWNTs incorporated binary systems at equal filler concentration. In contrast to the sharp decrease in tensile strength for TPV/SWNT composites, upon the addition of graphene into TPV/SWNT composite with a constant content of 0.5 wt% SWNTs, the increase in tensile modulus and tensile strength were 82% and 15% respectively at 2 wt % loading of graphene. Thermodynamic analysis was also applied to illustrate the different dispersion morphology of SWNTs and graphene in TPV. This study presents a new insight into the fabrication of high-performance TPV composites via the synergistic effects of hybrid fillers.

      PubDate: 2018-02-05T00:48:06Z
  • Efficient large-scale preparation of defect-free few-layer graphene using
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Chunyu Wang, Fuyou Ke, Wei Fan, Ye Chen, Fangyi Guan, Shiyan Chen, Huaping Wang
      It is very important to obtain large-scale and high-quality graphene for its application. However, the efficient preparation of large-scale and defect-free graphene is difficult by using a general method. In this report, a conjugated ionic liquid (IL) is designed and synthesized, which is used as a green medium to easily exfoliate graphite into graphene with the assistance of microwave irradiation. The as-prepared IL-functionized graphene nanoplatelets (GNPIL) is few-layer, large-size and defect-free, which is attributed to the strong π-π and cation-π interactions between conjugated IL and graphene layers. And the results show that a relatively high yield of 40% is obtained. The high-quality GNPIL could be dispersed in organic solvent homogeneously and stably with a high content, which is beneficial for its further applications. Furthermore, this GNPIL is used to composite with polyetherimide (PEI) to improve the conductivity of polymer. As compared with pure PEI, a sharp decrease of 11 orders of magnitude in volume resistivity is obtained for PEI composite with only 0.75 wt% GNPIL, which keeps a good mechanical property as well.

      PubDate: 2018-02-05T00:48:06Z
  • Fabrication and testing of composite hierarchical Isogrid stiffened
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Ming Li, Fangfang Sun, Changliang Lai, Hualin Fan, Bin Ji, Xi Zhang, Debo Liu, Daining Fang
      To get strong, stiff and light cylindrical shell, carbon fiber reinforced hierarchical Isogrid stiffened cylinder (HISC) was designed and fabricated. The cylinder has fractal stiffeners, including the first-order primary Isogrid stiffeners and the self-similar second-order sub-Isogrid stiffeners. The primary Isogrid has thick and high ribs and contains several sub-Isogrid cells whose rib is much thinner and lower. The primary Isogrid improves the bending rigidity of the cylindrical wall to resist the global instability while the sub-Isogrid improves the bending rigidity of the skin enclosed by the primary Isogrid to resist local buckling. The HISC was fabricated by filament winding method based on a silicone rubber mandrel with hierarchical grooves. Axial compression test was performed to reveal the failure mode. With hierarchical stiffeners, the cylinder balances the construction of the skin and the ribs and fails at material failure. Global instability and local buckling are both well restricted by the hierarchical stiffeners.

      PubDate: 2018-02-05T00:48:06Z
  • Microwave transparent crosslinked polystyrene nanocomposites with enhanced
           high voltage resistance via 3D printing bulk polymerization method
    • Abstract: Publication date: 22 March 2018
      Source:Composites Science and Technology, Volume 157
      Author(s): Yuanwu Chen, Jiale Mao, Jingshen Wu
      Demanded by the application in ultrahigh pulsed power generator as vacuum insulator, the MgO-filled nanocomposites with enhanced high voltage resistance were developed on the basis of microwave transparent crosslinked polystyrene (CPS). Considering the severe thermal runaway problem, a proprietary fabrication method combing the in-situ preparation with 3D printing bulk polymerization technique was also innovated and bulk products with different filler loading were successfully fabricated. The microscope images suggested that the distribution of MgO in the products was uniform, whereat the excellent mechanical properties of CPS were well maintained. Furthermore, owing to the appropriate dielectric characteristics of MgO and tiny filler loading, the relative permittivity of the composites increased very slightly while the loss tangent below 20 GHz was less than 8 × 10 − 4 , indicating the excellent transparency at the microwave band. Most importantly, the electrical breakdown strength was sharply improved from about 450 to over 600 kV/mm by only 0.1% MgO, as the barrier effect of electric double layer at the tremendous interface had effectively suppressed excessive charge injection and retarded electrical failure. Regarding the high voltage resistance obviously improved and the other properties well maintained, the CPS/MgO nanocomposites designed and developed in this work are applicable for the targeting application.

      PubDate: 2018-02-05T00:48:06Z
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