Journal Cover Composites Science and Technology
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   Hybrid Journal Hybrid journal (It can contain Open Access articles)
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   Published by Elsevier Homepage  [3120 journals]
  • 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
           photolithography
    • 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
           cylinder
    • 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
       
  • Enhanced thermal conductivity and mechanical property through boron
           nitride hot string in polyvinylidene fluoride fibers by electrospinning
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Dong-Li Zhang, Jun-Wei Zha, Wei-Kang Li, Chao-Qun Li, Si-Jiao Wang, Yongqiang Wen, Zhi-Min Dang
      The electrospun polyvinylidene fluoride (PVDF) based modified boron nitride (m-BN) composite with high thermal conductivity and flexible mechanical property was successfully fabricated by electrospinning method. The uniform dispersion and ordered orientation of m-BN in the m-BN/PVDF composites form a hot string, denoted as a series of thermal conduction fillers, in the direction of the fiber. Hence, the thermal conductivity of the m-BN/PVDF film could reach to 7.29 W m−1K−1 with the addition of 30 wt% m-BN. Besides, the obtained composites also show improved mechanical properties with the tensile strength of 24.06 MPa, low dielectric permittivity of 2.45 and dielectric loss of 0.0242 @ 103 Hz. Therefore, this work provides a new route to prepare the high thermal conductivity films with potential application as flexible power devices.

      PubDate: 2018-02-05T00:48:06Z
       
  • Pseudo-ductility in flexural testing of symmetric ±45° angle-ply
           CFRP laminates
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): M.C. Serna Moreno, S. Horta Muñoz, A. Romero Gutiérrez, C. Rappold, J.L. Martínez Vicente, P.A. Morales-Rodríguez, J.J. López Cela
      Pseudo-ductility could be sought in composite structures to avoid their brittle behaviour and, consequently, to withstand higher levels of external loading due to an extended non-linear response. This mechanism has been deeply examined in the literature for angle-ply laminates submitted to uniaxial tests. Nonetheless, the pseudo-ductile effects could appear also under flexural loading because tension and compression are applied in different regions of the cross-sections simultaneously. In this sense, bending testing presents a higher degree of complexity introduced by the variation of the strain through the cross-section thickness. Taking this into account the main scope of this work is to understand, describe, predict and optimise the pseudo-ductile flexural response of symmetric ±45° angle-ply laminates consisting of unidirectional and continuous CFRP plies. The outcome of three-point bending tests is reviewed analytically and experimentally. The analytical study considers the different behaviour of the material under tension and compression as well as the neutral fibre deviation from the mid-height plane. During testing the full normal strain field is acquired by means of a DIC system while strain-rosettes help to complete the data. The post-process based on microscopic characterization using SEM technology allows to observe the procedure of damage initiation and its evolution. Finally, the determination of the stacking sequences that minimise the bending-twisting coupling but favour the pseudo-ductile response is developed applying optimisation techniques with design purposes.

      PubDate: 2018-02-05T00:48:06Z
       
  • Chemical treatment of wood fibers to enhance the sound absorption
           coefficient of flexible polyurethane composite foams
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Hyeon Choe, Giwook Sung, Jung Hyeun Kim
      Polyurethane foams are commonly used as sound absorption materials in the automobile industry because their well-defined structure allows for effective absorption of sound waves through air friction and the structural vibration of cell walls. In this study, chemically treated wood fibers were incorporated into the polyurethane foams to improve their sound absorption coefficient by enhancing the compatibility between the wood fibers and the polyurethane matrix. The open porosity of the composite foams was strongly dependent on the chemical treatments of wood fibers as well as the wood fiber contents in the composites, and it was related to the air-flow resistivity and tortuosity of the foam materials. Model calculations revealed that high air-flow resistivity led to a high sound absorption coefficient, which agreed well with experimental observations. Therefore, for achieving high sound absorption performance in composite foams, no more than the optimum amount of a coupling agent must be used to improve the interfacial compatibility between the wood fibers and the polyurethane matrix. The use of excessive amount of the silane coupling agent led to intramolecular agglomeration, thus negatively affecting the sound absorption behavior.

      PubDate: 2018-02-05T00:48:06Z
       
  • Effects of elevated loading rates on mode I fracture of composite
           laminates using a modified wedge-insert fracture method
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Solver I. Thorsson, Anthony M. Waas, Joseph Schaefer, Brian Justusson, Salvatore Liguore
      In this paper, experimental results for rate dependence of interlaminar mode I fracture of a polymer matrix composite laminate are presented. A modified wedge-insert fracture (MWIF) method for conducting mode I fracture testing at elevated loading rates is used. A correction factor has been introduced to the modified beam theory method for measuring the mode I interlaminar fracture toughness using the MWIF method. The experimental method was successfully verified against the most widely used standardized method at quasi-static loading rates. Mode I interlaminar fracture testing was conducted at loading rates ranging from 0.01 mm/s to 3600 mm/s. A reduction in fracture toughness with rate was seen. The fracture behavior at elevated rates differed from the lower rates. The effect of bridging (and process zone) lengths on the fracture toughness were seen decreasing drastically with increased loading rate.

      PubDate: 2018-02-05T00:48:06Z
       
  • Post-functionalization of carboxylic polyethersulfone composite membranes
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Chen Wang, Yuan Xu, Shudong Sun, Changsheng Zhao
      Herein, a new and facile approach by in situ cross-linking polymerizationcoupled with a post-functionalization procedure was developed to prepare functional PES composite membranes to improve its over-all performance as hemodialysis membrane. In our strategy, poly(acrylate acid-co-2-hydroxyethyl methacrylate) P(AA-co-HEMA) as a macromonomer, was firstly synthesized by free radical copolymerization, then blended in PES solution and in situ cross-linked polymerization via the reaction of the hydroxy group of HEMA and the isocyanate group of 4,4′-diphenylmethane diisocyanate (MDI) to prepare the carboxylic membranes. To further enhance the hemocompatibility, the carboxylic membranes were post-functionalized by grafting sulfonic acid groups onto the membrane surfaces via a “grafting from” method. The chemical compositions and surface morphologies of the prepared membranes were investigated by ATR-FTIR, XPS, SEM and AFM. After introducing the functional groups, the surface hydrophilicity of the membranes was significantly improved, demonstrated by the reduced water contact angles (WCAs) and enhanced permeability. The decreased protein adsorptions and higher flux recovery ratios (FRRs) revealed that the modified membranes showed improved protein antifouling property. The improvement of hemocompatibility was confirmed by the inhibited platelet adhesion, prolonged clotting times, and suppressed blood-related complement activation. Moreover, the post-functionalized membranes also showed good cytocompatibility. In general, the in situ cross-linking technique is a suitable route in the field of membrane modification for its facile and easy operation; and the post-functionalization operation could endow the membranes with efficiently improved properties.

      PubDate: 2018-02-05T00:48:06Z
       
  • Glass fiber/epoxy composites with integrated layer of carbon nanotubes for
           deformation detection
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): P. Slobodian, S. Lloret Pertegás, P. Riha, J. Matyas, R. Olejnik, R. Schledjewski, M. Kovar
      An entangled multiwalled carbon nanotube film (Buckypaper) embedded in a polyurethane membrane was integrated into a glass fiber reinforced epoxy composite by means of a vacuum infusion to become a part of the composite and to give it a strain self-sensing functionality. In order to increase the strain sensing, pristine nanotubes were either oxidized by KMnO4 or Ag particles were attached to their surfaces. Moreover, the design of the carbon nanotube/polyurethane sensor allowed a formation of a film of micro-sized cracks, which increased its reversible electrical resistance and resulted in an enhancement of the strain sensing. Prestaining of the sensor with Ag-decorated nanotubes increased its sensitivity to strain, which was quantified by a gauge factor, more than hundredfold in comparison with the sensor with pristine nanotubes. The tests revealed that the integrated strain sensing exhibited a long-term electromechanical stability, which was linked to the level of strain in the host glass fiber/epoxy composite.

      PubDate: 2018-02-05T00:48:06Z
       
  • Significantly improved rubber-silica interface via subtly controlling
           surface chemistry of silica
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Chengfeng Zhang, Zhenghai Tang, Baochun Guo, Liqun Zhang
      It has been commonly acknowledged that particle dispersion and interfacial interactions are vital in determining the ultimate performance of polymer composites. However, the interplay between dispersibility and interfacial interaction in polymer composites has not been explicitly unraveled. In this contribution, a series of silica with controlled surface chemistry are prepared to reveal the effects of subtle change in surface property of filler on the structures and mechanical performance of the rubber composites. On the basis of thermodynamic theory, the dispersibility of modified silica in rubber is quantitatively evaluated by using surface energy. The modified silica was introduced into styrene-butadiene rubber (SBR) to investigate the effects of surface modification on the dispersion of silica and interfacial interaction of the rubber composites. It has been demonstrated that subtle change in surface chemistry of silica drastically improves its dispersibility in rubber matrix, leading to much improved accessible surfaces and hence much complete interfacial reaction. At very low grafting content (0.2 molecule/nm2), improved modulus (44%) and wet-traction (54%), together with reduced rolling-resistance (11%), are concurrently observed.

      PubDate: 2018-02-05T00:48:06Z
       
  • A polymer-coated calcium chloride hexahydrate/expanded graphite composite
           phase change material with enhanced thermal reliability and good
           applicability
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Kunjie Yuan, Yan Zhou, Wanchun Sun, Xiaoming Fang, Zhengguo Zhang
      A novel polymer-coated composite PCM was prepared by mixing the CaCl2·6H2O/EG composite particles with a photo-curing polymer, followed by irradiating the mixture under UV light to make the polymer cured. It is shown that the surfaces of the composite particles have been sealed by the polymer. And the melting and freezing enthalpy values of the obtained polymer-coated CaCl2·6H2O/EG composite PCM are as high as 113.2 and 114.1 J g−1, respectively, and its melting point is quite close to that of CaCl2·6H2O. After experiencing 500 heating-cooling cycles, polymer-coated CaCl2·6H2O/EG exhibits the decreases only by 1.68% and 0.52% in the enthalpies of melting and freezing, much less than 25.54% and 30.55% for CaCl2·6H2O/EG, respectively, revealing much enhanced thermal reliability. The applicability of the uncoated and polymer coated CaCl2·6H2O/EG composite PCMs was investigated by directly mixing them with gypsum powder and water, followed by forming into plasterboards. It is found that, the plasterboard containing polymer coated CaCl2·6H2O/EG not only exhibits superior thermal performance for delaying temperature rise over the one with CaCl2·6H2O/EG but also possesses much better thermal reliability. These good characteristics render the polymer-coated CaCl2·6H2O/EG composite PCM with great potentials in building energy conversation.

      PubDate: 2018-02-05T00:48:06Z
       
  • Simultaneously improved electromagnetic interference shielding
           and mechanical performance of segregated carbon nanotube/polypropylene
           composite via solid phase molding
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Hong-Yuan Wu, Li-Chuan Jia, Ding-Xiang Yan, Jie-feng Gao, Xiao-Peng Zhang, Peng-Gang Ren, Zhong-Ming Li
      Conductive polymer composite with segregated structure has been well demonstrated to achieve high electromagnetic interference shielding effectiveness (EMI SE) due to the selectively distributed electrical nanofillers to establish desirable conductive networks. Nevertheless, the formation of segregated structure in low-melt-viscosity semi-crystalline polymer is still challenged and the segregated composite always suffers poor mechanical performance. Herein, elevated pressure and temperature were utilized to make a typical semi-crystalline polymer, polypropylene (PP), hold solid phase to restrict the diffusion of carbon nanotube (CNT) into its interior. Segregated CNT networks were facilely constructed in the resultant CNT/PP composite and imparted it with a superior EMI SE of 48.3 dB at 2.2 mm thickness and 5.0 wt% CNT loading, the highest EMI shielding level among the reported CNT/polymer composites at equivalent material thickness and CNT loading. Moreover, the elevated pressure and temperature effect dramatically increase the compressive, tensile, and flexural strength (modulus) of the CNT/PP composite by 133% (65%), 74% (130%) and 53% (50%), respectively, in comparison to those for conventional segregated CNT/PP composite, really overcoming the major mechanical shortcoming in the development of segregated composites for EMI shielding. Our work provides a facile strategy to fabricate the efficient EMI shielding and robust material with the construction of typical segregated structure in low-melt-viscosity semi-crystalline polymers.

      PubDate: 2018-02-05T00:48:06Z
       
  • Enhanced thermal and fire retardancy properties of polypropylene
           reinforced with a hybrid graphene/glass-fibre filler
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Dimitrios G. Papageorgiou, Zoe Terzopoulou, Alberto Fina, Fabio Cuttica, George Z. Papageorgiou, Dimitrios N. Bikiaris, Konstantinos Chrissafis, Robert J. Young, Ian A. Kinloch
      The thermal stability and flame retardancy properties of polypropylene (PP) nanocomposites containing graphene nanoplatelets (GNPs), glass fibres (GFs) or a hybrid mixture of the two fillers were investigated. The GNPs enhanced the thermal stability of the nanocomposites by at least 48 °C as a result of the nanoconfinement of the polypropylene chains and the prevention of the emission of the gaseous molecules during decomposition. Pyrolysis combined with gas chromatography and mass spectroscopy showed that the decomposition mechanism of the polymer was not altered by the presence of the nanofillers and the alkenes that comprised of 3n carbon atoms were the main degradation products. Cone calorimetry tests revealed a significant delay of the ignition under irradiation with the addition of GNPs to the PP. Furthermore, the GNPs lowered the combustion rate of the PP due to the formation of a carbonaceous protective layer that acted as a barrier to heat and mass transfer. The lightweight materials prepared show promising results for applications where high thermal stability along with fire retardancy are a prerequisite, such as parts for vehicles or aircraft.

      PubDate: 2018-02-05T00:48:06Z
       
  • Highly conductive nanocomposites based on cellulose nanofiber networks via
           NaOH treatments
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Chuchu Chen, Mengmin Mo, Wenshuai Chen, Mingzhu Pan, Zhaoyang Xu, Haiying Wang, Dagang Li
      Developing functional nanocomposites with the utilization of the sustainable natural resources (e.g. cellulose) is one most importance strategy. In this study, a novel method was developed and used to fabricate flexible conductive nanocomposite. The key innovation of this method is that carbon nanotubes (CNTs) was incorporated into cellulose nanofiber (CNF) gel which processed by alkali treatment. We found that the gelation process caused the shrinking of CNF/CNT gel-film, which result in forming a robust 3D network structure. While the shrinking attributed to constructing high density CNTs electron transport pathways and achieve improved electrical conductivity. Results clearly show that CNFs, a dispersing agent, were used to well-dispersed the CNTs in the nanocomposite. After the alkali treatments, the as-prepared CNF/CNT gel-film had a conductivity of 5.02 S/cm, which is almost 3-fold higher than the CNF/CNT film (without alkai treatment), at 20 wt% CNTs. Conductivity of the CNF/CNT gel-film was further improved to as high as 17.04 S/cm, when adding 50 wt% CNTs. Morphology investigation exhibited that CNFs and CNTs formed into a high density 3D network affording adequate electron transport pathways, and giving the gel-film remarkable electrical conductive properties. Additionally, in lights of its excellent electrical performance, low cost, and environmental friendliness, the CNF/CNT gel-film may have a promising application in the flexible electrodes and conductive papers.

      PubDate: 2018-02-05T00:48:06Z
       
  • Surface modified BaTiO3 nanoparticles by titanate coupling agent induce
           significantly enhanced breakdown strength and larger energy density in
           PVDF nanocomposite
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Penghao Hu, Shengmin Gao, Yangyang Zhang, Liang Zhang, Chengchen Wang
      Dielectric capacitors are promising in micro-electronics, portable equipment and hybrid electric vehicles due to their specific features of flexibility, ultrahigh operating voltage and fast charging-discharging rate. The dielectric properties of polymer-based nanocomposite are much related to the interface binding between fillers and matrix. In this work, a surface modification approach employed newfound titanate coupling agent was developed to improve the compatibility between BT nanoparticles and PVDF matrix. After treated by the modifier TC-2, a coating layer contained with active organic groups was formed on the surface of BT nanoparticles. Benefited from the improved dispersibility and compatibility of modified BT nanoparticles in PVDF matrix, the breakdown strength of the nanocomposites was much enhanced. The monodisperse mBT-2 nanoparticles treated with appropriate amount of modifier dramatically enlarged the breakdown strength from 397 kV/mm for neat PVDF to 517 kV/mm for 4 vol% mBT-2 loading nanocomposite. Compared with BT/PVDF, the improvements on the energy storage performance in mBT-2/PVDF are significant. The maximum discharged energy density of 11.27 J/cm3 for 4 vol% loading mBT-2/PVDF is nearly double of that for 4 vol% loading BT/PVDF, and the energy efficiency for mBT-2/PVDF is also increased. The modification method originally represented here has great potential in developing high energy density nanocomposites for advanced applications.

      PubDate: 2018-02-05T00:48:06Z
       
  • Electric field-induced alignment of nanofibrillated cellulose in
           thermoplastic polyurethane matrix
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Shuman Xu, Dingyao Liu, Qin Zhang, Qiang Fu
      Nanofibrillated fibers (NFC) has been largely used as reinforcing filler to improve the properties of polymer matrix because of their unique properties such as high aspect ratio, good aqueous stability, high specific strength and stiffness. However, the full potential of NFC as reinforcing agent has not been realized because of its poor dispersion and random distribution in polymer matrix. In this work, we demonstrate the importance of alignment of NFC to determine the mechanical properties of polymer via applying alternative current (AC) electric field and using thermoplastic polyurethane (TPU) as the matrix. The TPU/NFC nanocomposites were prepared via solution casting method and the effect of parameters of the applied electric field (amplitude, frequency as well as the duration of application) on the orientation degree of NFC and the final properties of TPU/NFC nanocomposites are systematically investigated. It was found that NFC could be easily oriented under effect of AC due to electric induced polarization. The prepared anisotropic TPU/NFC composites exhibit 2.07 and 1.82 times increase of tensile strength and elongation at break in the parallel direction than that in the vertical direction for the anisotropic samples, respectively. It was also interesting, to find that the samples with aligned NFC exhibit an increased dielectric constant with lower dielectric loss, which could provide an idea to fabricate high performance dielectric materials.

      PubDate: 2018-02-05T00:48:06Z
       
  • Fabrication and testing of composite corrugated-core sandwich cylinder
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Wanxin Li, Fangfang Sun, Weiyi Wei, Debo Liu, Xi Zhang, Ming Li, Hualin Fan
      To get a strong, stiff and weight efficient cylindrical shell, carbon fiber reinforced corrugated-core sandwich cylinders (CSCs) were designed and made. The corrugated-core is made up of corrugated cylindrical shell and manufactured by mould hot pressing method. Split forming and integral filament winding forming methods were applied to make the CSC separately. Effects from non-wrapped and wrapped cylindrical ends were investigated individually. Uniaxial compression tests were performed to reveal the strength and failure mode. Split forming method makes the CSC stiffer but integral filament winding forming method makes the CSC stronger. With non-wrapped ends, the cylinders fail at end delamination and the load carrying capacity is 289.7 kN and 373.7 kN, respectively. The load is improved to 415.6 kN and 491.4 kN, respectively, when the cylinder is end-wrapped. Skin fracture controls the failure of the CSCs with wrapped ends and makes them stronger. Meanwhile, the load carrying ability of the CSC is stronger than lattice truss-core sandwich cylinders (LTSCs). Benefiting from the high axial load carrying ability of the CFRC corrugated shell, strength of the designed CSC failing at skin fracture improves at a magnitude of 50% compared with the referenced LTSC.

      PubDate: 2018-02-05T00:48:06Z
       
  • A facile approach to constructing efficiently segregated conductive
           networks in poly(lactic acid)/silver nanocomposites via silver plating on
           microfibers for electromagnetic interference shielding
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Kai Zhang, Hai-Ou Yu, Kai-Xin Yu, Yuan Gao, Ming Wang, Jiang Li, Shaoyun Guo
      Here, a facile approach to constructing efficiently segregated conductive networks in the poly(lactic acid)/silver (PLA/Ag) nanocomposites were developed by coating Ag particles on PLA microfibers and then compression molding. The electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE) of the nanocomposites were obviously enhanced by these efficiently conductive networks because of the well Ag coating layers on PLA microfibers. Furthermore, the electrical conductivity and the EMI SE of the nanocomposites increased with increasing the coating amount of Ag particles, which can be easily tuned by controlling the coating time. It was found that the chain-structured PLA/Ag nanocomposites with coating time of 7 min with 5.89 vol% Ag particles possessed the remarkable electrical conductivity of 254 S/m and outstanding EMI SE of 50 dB at 8.2–12.4 Hz when the testing samples with the thickness of 1.5 mm, which far surpassed the targeted value of 20 dB for commercial applications. The excellent EMI shielding properties of the nanocomposites were ascribed to the unique segregated chain-structures, which provide enormous interfaces to reflect, scatter and adsorb the electromagnetic waves many times. The PLA/Ag nanocomposites with segregated networks were also found to be an absorption dominated EMI shielding mechanism.

      PubDate: 2018-02-05T00:48:06Z
       
  • Largely enhanced electrical conductivity of layer-structured silver
           nanowire/polyimide composite films by polyaniline
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Fang Fang, Gui-Wen Huang, Hong-Mei Xiao, Yuan-Qing Li, Ning Hu, Shao-Yun Fu
      Electrical conductivity (σ) and mechanical properties are two major concerns for layer-structured films used in electronic devices. It is unavoidable to significantly reduce the mechanical integrity of layer-structured films for adjoined conducting-layer and polymer layer and also greatly increase the cost for expensive conductive fillers in order to enhance σ by simply increasing conducting filler content. This paper reports for the first time the preparation of silver nanowire (Ag-NW)/polyimide (PI) layer-structured composite films with greatly enhanced σ and maintained good mechanical properties by polyaniline (PANI) utilized in the PI substrate layer to regulate its potential barrier for the purpose of reducing the tunnelling resistance between Ag-NWs. Consequently, σ is greatly enhanced by up to 8.7 times (over 1000 S/cm) while the high tensile strength of the layer-structured conducting composite film is maintained by 95% (over 75 MPa) via introduction of PANI at low contents up to 20% of PI. This work provides a simple strategy for development of high-quality thin films for electronic devices simultaneously possessing high σ and good mechanical properties.

      PubDate: 2018-02-05T00:48:06Z
       
  • All-aromatic SWCNT-Polyetherimide nanocomposites for thermal energy
           harvesting applications
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Lazaros Tzounis, Maruti Hegde, Marco Liebscher, Theo Dingemans, Petra Pötschke, Alkiviadis S. Paipetis, Nikolaos E. Zafeiropoulos, Manfred Stamm
      The thermoelectric properties of amorphous and semi-crystalline high-performance polyetherimide–SWCNT nanocomposites are reported for the first time. Nanocomposites based on a non-linear polyetherimide (PEI) model system, labeled aBPDA-P3, with 0.6, 4.4 and 10 vol% SWCNTs remained amorphous after the addition of SWCNTs. In contrast, SWCNTs induced crystallization in a linear PEI model system labeled as ODPA-P3. The (thermo)mechanical properties were fully characterized using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMTA). The electrical conductivity was studied by four-probe measurements and showed higher values for the ODPA-P3 films reaching 20 S/m at 10 vol% of SWCNTs. The thermoelectric performance revealed by Seebeck coefficient (S) measurements showed values of 40 and 55 μV/K for the 0.6 and 4.4 vol% ODPA-P3 SWCNT nanocomposites, while 16 and 47 μV/K for aBPDA-P3 amorphous films. This enhancement has been attributed to SWCNT–induced crystallization in ODPA-P3 matrix. The PEI-SWCNT nanocomposites are ideal candidates as organic flexible films and coatings for large area thermal energy harvesting, where high temperature gradients exist. Potential applications can be envisaged in the aerospace, automotive and micro-electronics sectors.

      PubDate: 2018-02-05T00:48:06Z
       
  • Advanced piezoresistive sensor achieved by amphiphilic nanointerfaces of
           graphene oxide and biodegradable polymer blends
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Roberto Scaffaro, Andrea Maio, Giada Lo Re, Antonino Parisi, Alessandro Busacca
      This work focuses on the preparation of a piezoresistive sensor device, by exploiting an amphiphilic sample of graphene oxide (GO) as a compatibilizer for poly (lactic acid) (PLA)-Poly (ethylene-glycol) (PEG) blends. The presence of GO determined a high stiffening and strengthening effect, without affecting toughness, and allowed a good stability of mechanical properties up to 40 days. Moreover, GO endowed the materials with electrical properties highly sensitive to pressure and strain variations: the biodegradable pressure sensor showed a responsivity of 35 μA/MPa from 0.6 to 8.5 MPa, a responsivity around 19 μA/MPa from 8.5 to 25 MPa. For lower pressure values (around 0.16–0.45 MPa), instead, the responsivity increases up to 220 μA/MPa in terms of ΔI/ΔP (i.e. (ΔI/ΔI0)/P close to 1 kPa−1). Furthermore, this novel sensor is able to monitor submicrometric displacements with an impressive sensitivity (up to 25 μA/μm in terms of ΔI/ΔL, or 70 in terms of (ΔI/I0)/ε). We implemented a model able to predict pressure changes up to 25 MPa, by monitoring and measuring variations in electrical conductivity, thus paving the road to use these biodegradable, ecofriendly materials as low-cost sensors for a large pressure range.

      PubDate: 2018-02-05T00:48:06Z
       
  • Low cost and facile preparation of robust multifunctional coatings with
           self-healing superhydrophobicity and high conductivity
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Kunlin Chen, Weiwei Gou, Le Xu, Yan Zhao
      Superhydrophobic and conductive multifunctional coatings have been receiving great attention in recent years due to their wide potential applications. Nevertheless, a simple and cost-effective approach is still lacked. Herein, photocatalytic TiO2 nanoparticles and graphite particles were blended with fluorinated polysiloxane and methyltris(methylethylketoxime)silane, and followed by simply spraying onto various substrates for superhydrophobic functionalization under ambient-drying, in which the graphite particles and TiO2 nanoparticles could not only lead to the micro/nano-roughness structures for coatings but also endow the coatings with the conductivity and photocatalysis. These as-prepared coatings are not only superhydrophobic but also have the high conductivity. They also can be coated on the fabrics for the oil/water separation and deposited on flammable objects as the fire-shielding layer. This multifunctional coating is robust under the external taped or pressed forces and very stable whether in the acid-alkali and salty environment or during long hours of UV irradiation. And most of all, this coating could repair its superhydrophobicity even after mechanically abraded or polluted with organics. The design and fabrication of this multifunctional coating may find immediate usage in a wide range of areas.

      PubDate: 2018-02-05T00:48:06Z
       
  • Mechanically strong polyimide / carbon nanotube composite aerogels with
           controllable porous structure
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Wei Fan, Lizeng Zuo, Youfang Zhang, Ye Chen, Tianxi Liu
      Developing aerogels with controllable pores, outstanding mechanical properties and excellent thermal stability still remains a key challenge in evolution of aerogels. In the present work, polyimide (PI) composite aerogels with controllable porous structures and tunable multi-functions have been fabricated with the addition of carbon nanotubes (CNTs) with different functional groups and aspect ratio via an eco-friendly freeze-drying method followed by a thermal imidization process. The interactions between PI chains and CNTs can form crosslinking points through physical or chemical bonding, which could overcome the expansive force in the ice crystal growth process and the capillary force during ice sublimation, thus forming a three-dimensional porous structure. Through increasing the content of functional groups on CNTs, the PI/CNT composite aerogels show enhanced structural stability with a less shrinkage (<20%) during processing, further resulting in improved mechanical properties. As a result, the PI composite aerogels exhibit low density (∼0.1 g cm−3), improved compression modulus (33.5 MPa), and high thermal stability (above 580 °C), showing great potential for application as lightweight and high-performance materials. Additionally, this work develops a new strategy to realize the controllable preparation and tunable properties of polymer aerogels by utilizing nanofillers as an effective crosslinking agent.

      PubDate: 2018-02-05T00:48:06Z
       
  • Toward biomimetic porous poly(ε-caprolactone) scaffolds: Structural
           evolution and morphological control during solid phase extrusion
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Hua-Mo Yin, Yan-Fei Huang, Yue Ren, Peng Wang, Baisong Zhao, Ji-Hua Li, Jia-Zhuang Xu, Zhong-Ming Li
      Two-dimensional oriented scaffolds bear spatial limitation to regenerate three-dimensional (3D) tissues despite showing the ability to guide cell alignment and elongation. By combining solid phase extrusion (SPE) of co-continuous blends with phase removal, we prepared an interconnected 3D porous poly(ε-caprolactone) (PCL) scaffold with oriented pores. To better regulate structure of these distinctive scaffolds, structural evolution of co-continuous blends in the convergent die during SPE was investigated in this study. Morphological observation manifested that the elongation deformation of co-continuous blends proceeded along the extrusion direction in the converging die continuously. Due to the extrusion temperature below the melting point of the matrices, the aligned co-continuous phase was maintained to form the uniformly oriented pores after phase extraction. Unlike consecutive deformation of phase morphology, the change in the crystalline structure of PCL involved two stages divided by the critical deformation distance (∼10 mm). At stage I (<10 mm), spherical crystals of PCL transformed into ellipsoidal shape owing to plastic deformation. At stage II (>10 mm), organized PCL lamellae formed along the extrusion direction as a result of crystal fragmentation and rearrangement. On the basis of anterior cognition, effects of processing parameters on porous morphology were further explored. It was revealed that extrusion draw ratio and annealing time were more effective to regulate pore orientation and size of aligned porous scaffolds than extrusion temperature. The tunable morphological structure of biomimetic scaffolds is of vital importance to broaden their applications for tissue repair.

      PubDate: 2018-02-05T00:48:06Z
       
  • Dispersion of nanoparticles in polymer matrices with well-designed ligands
           as dispersant/emulsifier/comonomer
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Yong Ding, Yu Chen, Junping Zheng
      Dispersing nanoparticles in polymers is a key requirement for the development of polymer-matrix composites. In this study, cationic ligand and anionic ligand were designed to serve as dispersant, emulsifier and comonomer in different stages of nanocomposites preparation. Commercial BaTiO3, TiO2, Ag and Al2O3 nanoparticles were incorporated and dispersed uniformly in polystyrene (PS) and polymethyl methacrylate (PMMA) matrices by designed cationic/anionic ligand. As dispersants, the sizes of nanoparticles aggregates were reduced from thousands of nanometers to dozens of nanometers by cationic/anionic ligand. Then ligands served as emulsifiers to prepare polymer nanocomposites. At the end of emulsion polymerization, the ligands copolymerized with polymer matrices. At this stage, the sizes of nanoparticles in polymer matrices fell to several nanometers. After hot-pressing, nanoparticles maintained the stable dispersion state in polymer matrices. The tensile strength of P(MMA-co-VDAC)/BaTiO3 increased by 77% compared with PMMA. The thermal decomposition temperature of P(St-co-MAMS)/Al2O3 was improved by 24 °C compared with PS. A facile and efficient approach was exhibited for preparing polymer nanocomposites with a large variety of chemically different nanoparticles in diversified polymer matrices.

      PubDate: 2018-02-05T00:48:06Z
       
  • Competing mechanisms in the unfolding failure in composite laminates
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): J.M. González-Cantero, E. Graciani, B. López-Romano, F. París
      Highly-curved laminates are prone to fail by delamination when they are loaded under a bending moment which tries to flatten the laminate. This failure, commonly called unfolding failure, has been traditionally associated with the tensile interlaminar stresses which appear in the laminate, due to its high curvature. However, some specimens failing by unfolding present a maximum interlaminar tensile stress, at the failure instant, much lower than other specimens with different thicknesses or stacking sequences. This fact has been commonly associated with a thickness dependence of the interlaminar tensile strength for which no physical explanation can be found in the literature, although sometimes it has been attributed to manufacturing defects, which are assumed to be higher in thinner laminates. The present work considers the idea of a second failure mechanism named induced unfolding, which assumes that an intralaminar failure is responsible for the failure onset. Therefore, in some cases, the unfolding failure starts as an intralaminar crack which, under a high enough interlaminar tensile stress, propagates instantaneously, causing the delamination and the final failure. Analysing the results of a test campaign, proofs of the occurrence of this kind of failure on L-shape CFRP laminates of UD plies are reported.

      PubDate: 2018-02-05T00:48:06Z
       
  • Conducting α-Fe2O3 nanorod/polyaniline/CNT gel framework for high
           performance anodes towards supercapacitors
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Zhaokun Yang, Aidong Qiu, Jun Ma, Mingqing Chen
      Thick-electrode design toward high energy density per device is of particular importance for supercapacitors to store large amount of energy, but this remains a seemingly insurmountable challenge due to sluggish electron transport. The challenge is addressed herein by developing an electrically and ionically conducting framework which consists of α-Fe2O3 nanorods, multi-walled carbon nanotubes (CNTs) and polyaniline (PANi) hydrogel. The interconnecting composite framework is formed by in situ polymerizing aniline on the surface of α-Fe2O3 nanorods and CNTs; the nanorods are found to well disperse in the matrix. The framework can provide low-resistance, continuous transport pathways for both electrons and electrolyte ions in the entire electrode system, maximizing the energy use of the nanorods. An anode of ∼100 μm in thickness is fabricated using the composite framework, corresponding to a mass loading of 9.3 mg cm−2. It delivers high area capacitance of 2434.7 mF cm−2 and cycling capacitance retention of 96.3% after 10,000 cycles. This work would shed light on the design of thick electrodes toward high-capacity energy storage devices.

      PubDate: 2018-02-05T00:48:06Z
       
  • An in-situ formable and fibrils-reinforced polysaccharide composite
           hydrogel by self-crosslinking with dual healing ability
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Bihua Ye, Shuyun Zhang, Riwang Li, Lihua Li, Lu Lu, Changren Zhou
      Novel in-situ formable and fibrils-reinforced polysaccharide-based composite hydrogels with dual healing ability were prepared by a facile, one-pot approach with maleilated chitosan (CS-MA) and thiol derivatised sodium alginate (SA-SH), via Michael addition reaction and ionic interaction. The unique fibrils network working as reinforcement fillers were attributed to the electrostatic interaction of CS-MA with SA-SH. This CS-MA/SA-SH composite hydrogel can self-heal cracks through dynamic disulfide exchange in 12 h at 37 °C without any external intervention. Noteworthy, fast healing ability inside hydrogels or with porous scaffolds within 1 min can be obtained via the introduction of calcium ions. Moreover, tunable shapes can also be obtained via dual cross-linking, providing advantages to optimize the fibrils-reinforced composite gels system for more biomedical applications. In addition, cell viability and proliferation showed that both of the gels before and after healing with Ca2+ possessed good cytocompatibility.
      Graphical abstract image

      PubDate: 2018-02-05T00:48:06Z
       
  • Interfacial designing of PP/GF composites by binary incorporation of
           MAH-g-PP and lithium bis(trifloromethanesulfonyl)imide: Towards high
           strength composites with excellent antistatic performance
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Senlin Gu, Huanhuan Liu, Xuan Li, Claude Mercier, Yongjin Li
      High strength polypropylene (PP)/glass fiber (GF) composites with excellent antistatic performance were prepared by binary incorporation of maleic anhydride grafted polypropylene (MAPP) and lithium bis(trifloromethanesulfonyl)imide (Li-TFSI) into PP/GF composites. Li-TFSI was used as antistatic agents and MAPP was added as the interfacial binder between GF and PP matrix. It was found that the interface between PP and GF can be tuned by the binary addition of MAPP and Li-TFSI. The mechanical properties of PP/GF composites are enhanced drastically with the addition of MAPP. However, Li-TFSI induces the decreasing of the mechanical properties with enhanced antistatic performance of the composites. The investigation showed that Li-TFSI, as a high polar agent, breaks the physisorbed silane on the glass fiber, which induces the deterioration in the strengthening effects of MAPP. At the same time, the Li-TFSI is absorbed on the surface of GF and the ions are ready to move along the GF, so the antistatic performance is achieved. The specific interactions between Li-TFSI, GF and MAPP make it possible to design the interface of PP/GF composites by the binary incorporation of MAPP and Li-TFSI. Therefore, high performance PP/GF composites with both excellent antistaticity and high strength can be achieved.
      Graphical abstract image

      PubDate: 2018-02-05T00:48:06Z
       
  • Silkworm silk fibers vs PEEK reinforced rubber luminescent strain gauge
           and stretchable composites
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Luca Valentini, Silvia Bittolo Bon, Lorenzo Mussolin, Nicola M. Pugno
      In the present study we demonstrate how the sensitive property of the constituent parts of silkworm silk fiber can be applied to the field of soft composite materials. It concerns the structural and intrinsic functional characteristics of silk vs. the macroscopic property and the realization of functional composites. Silk fiber reinforced silicone rubber (SR) composites have been fabricated with different fiber lengths. The key structural features of silk made of stiff nanocrystals, including hydrogen bonded β-strands and β-sheet nanocrystals, when embedded in a softer matrix demonstrate that the tensile strength as well as the stiffness of the composites are higher than those measured for SR reinforced with synthetic polyether-ether-ketone fibers. Moreover, the intrinsic luminescence of protein nanocrystals permits the direct observation of the deformation with accurate measurement of the strain in the composite. Based on the intrinsic properties of such natural hierarchical material, these findings will allow to transfer the engineering of composite materials, particularly, soft functional composites, to a new applications ranging from strain measurements in biological tissue to monitoring tool in structural composites.

      PubDate: 2018-02-05T00:48:06Z
       
  • Unraveling crack stability and strain localization in staggered composites
           by fracture analysis on the shear-lag model
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Zhongliang Yu, Junjie Liu, Xiaoding Wei
      Bio-inspired composites can achieve excellent toughness while maintaining their strength through hierarchical microstructure designs combining strong and brittle reinforcements and soft yet ductile matrices. The interfaces between reinforcements and matrices transfer loads through shear deformation and deflect cracks along themselves to dissipate a considerable amount of energy. In this way, the catastrophic failure, which is common in monolithic reinforced materials due to the severe stress concentration near the defects, is deferred in hierarchical composites. Yet, recent computations and experiments suggest that strain localization arising from the unstable crack propagation along interfaces leads to the composites failure. In this study, fracture analysis is carried out on staggered composites with the brick-and-mortar structure. An analytical formula predicting the onset of strain localization emerges from the analysis and is validated by finite element analysis. Furthermore, showing good agreements with independent tensile tests on multi-layer graphene assemblies, our model demonstrates its applicability to explain the strain localization in composites consisting of interfaces that function through re-formable bonds. Characteristic length scales emerging from the analysis can be used to guide the composites design to optimize material toughness and ductility.

      PubDate: 2018-02-05T00:48:06Z
       
  • Strong, transparent and flexible aramid nanofiber/POSS hybrid
           organic/inorganic nanocomposite membranes
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Fang Wang, Yadong Wu, Yudong Huang, Li Liu
      Mechanical performance, transparency and thermal stability still remain the dominating constraints for the application of polymeric composite membranes. Thus, the research and development of co-effectively strong, transparent and heat-resistant membranes are necessary and significant for promoting practical outcomes. POSS NPs is incorporate into the structure of aramid nanofibers (ANFs) to synthesize the ANFPs nanocomposite membranes with different amounts of POSS by vacuum-assisted flocculation. FT-IR and XPS were applied to characterize the structure of composite membranes. Upon the addition of POSS, the surface topological structures of composite membranes were not affected, and they retained excellent transparency and flexibility. The mechanical properties of ANFPs membranes could be altered by changing the POSS content, in which the POSS served as a cross-linking agent between nanofibers, and ANFPs composite membrane presented the optimal tensile strength with 6 wt% POSS embedding in the nanocomposite. Besides the excellent mechanical performance and transparency, the unique thermal assets of ANFs and POSS further enabled the membranes with high thermal stability. Based on these results, it could be concluded that the ANFPs membranes developed here might provide the alternative materials for the practical application of strong, transparent and heat-resistant membrane.

      PubDate: 2018-02-05T00:48:06Z
       
  • A highly stretchable and stable strain sensor based on hybrid carbon
           nanofillers/polydimethylsiloxane conductive composites for large human
           motions monitoring
    • Abstract: Publication date: 1 March 2018
      Source:Composites Science and Technology, Volume 156
      Author(s): Yanjun Zheng, Yilong Li, Kun Dai, Yan Wang, Guoqiang Zheng, Chuntai Liu, Changyu Shen
      Stretchable strain sensors have promising potentials in wearable electronics for human motion detection, health monitoring and so on. A reliable strain sensor with high flexibility and good stability should be designed to detect human joints motions with a large deformation. Here, a simple and facile solution mixing-casting method was adopted to fabricate a highly stretchable strain sensor based on composites mixing polydimethylsiloxane (PDMS) with hybrid carbon nanotubes (CNTs) and carbon black (CB) conductive nanofillers (CNTs-CB). Bridged and overlapped hybrid CNTs-CB nanofillers structure was achieved in the composite on the basis of the morphology observation. In monotonic stretching test, the CNTs-CB/PDMS composites strain sensors exhibited high stretchability, strain-dependent sensitivity in a wide strain sensing range (ca. 300% strain) and an excellent linear current-voltage behavior. During stretching-releasing cycles, the strain sensors presented excellent repeatability, good stability and superior durability (2500 cycles at 200% strain). Combined with the above outstanding strain sensing performances, the fabricated stretchable strain sensors were attached onto different joints of human body to monitor the corresponding human motions, demonstrating their attractive perspective in large human motions detection.

      PubDate: 2018-02-05T00:48:06Z
       
  • Graphite nanosheets - polypropylene composites from in toluene delaminated
           graphite using atactic polypropylene as dispersant
    • Abstract: Publication date: Available online 26 December 2017
      Source:Composites Science and Technology
      Author(s): A. Rosehr, D. Griebe, G.A. Luinstra
      Composites of polypropylene (PP) and graphite nanosheets (GN) are prepared by melt blending PP with a master batch of GN suspended in atactic polypropylene (Mw = 129.000 g/mol). aPP/GN master batches were obtained by wet ball-milling graphite in toluene using the aPP as dispersant. The procedure gives single flakes of GN with crystallite out-of-plane thickness as low as 17.7 nm. PP/aPP/GN composites were obtained with finely dispersed GN, predominantly as single nanosheets from master batches containing aPP dispersant and graphite. Crystallization of the iPP in the composites is facilitated by the presence of aPP and GN. PP spherulites are formed as the graphitic fillers act as strong nucleating agents: the dimensionality of the crystal growth (n = 2-3) and the crystallinity increases with increasing filler content in isothermal and non-isothermal crystallizations. The yield strength of the composites can be enhanced up to 20% by the presence of GN; the presence of aPP counteracts a decrease in elongation at break. Composites prepared from parent graphite or GN without aPP show larger aggregates of nanosheets in the composites.

      PubDate: 2017-12-27T01:12:05Z
       
  • A new low moduli dielectric elastomer nano-structured composite with high
           permittivity exhibiting large actuation strain induced by low electric
           field
    • Abstract: Publication date: Available online 26 December 2017
      Source:Composites Science and Technology
      Author(s): Feixiang Zhang, Tiefeng Li, Yingwu Luo
      Dielectric elastomers (DEs) are able to deform significantly in response under an external electric field. DE actuators have promising applications in many emerging fields such as biomimetic robots, haptic devices, tunable lens, and loudspeakers. Practical applications of DE devices are limited by the extremely high electric field and the high pre-stretch. Herein, we have designed and fabricated a new type of soft DE composites of partially reduced graphene oxide (RGO)/polystyrene-b-poly (n-butyl acrylate)-b-polystyrene triblock copolymer (SBAS). An extremely soft SBAS was tailor-made as the elastic matrix. A facile colloidal blending method, i.e. simply mixing the SBAS latex with GO aqueous dispersion, was used to fabricate the nano-structured composite with a segregated network of RGO nanosheets. The design strategy led to the DE composite film of 1.5 wt% RGO/SBAS owning low modulus (0.51 MPa), high relative permittivity (∼11) and relatively high dielectric breakdown strength (33 kV/mm). The DE composite film exhibited 21.3% maximum area actuation strain at relatively low electric field strength 33 kV/mm without pre-stretch.

      PubDate: 2017-12-27T01:12:05Z
       
 
 
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