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Showing 1 - 200 of 1205 Journals sorted alphabetically
3 Biotech     Open Access   (Followers: 7)
3D Research     Hybrid Journal   (Followers: 19)
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Adıyaman Üniversitesi Mühendislik Bilimleri Dergisi     Open Access  
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Analele Universitatii Ovidius Constanta - Seria Chimie     Open Access  
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at - Automatisierungstechnik     Hybrid Journal   (Followers: 1)
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Balkan Region Conference on Engineering and Business Education     Open Access   (Followers: 1)
Bangladesh Journal of Scientific and Industrial Research     Open Access  
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Boundary Value Problems     Open Access   (Followers: 1)
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Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 40)
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Catalysis Today     Hybrid Journal   (Followers: 5)
CEAS Space Journal     Hybrid Journal  
Cellular and Molecular Neurobiology     Hybrid Journal   (Followers: 4)
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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)
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Cientifica     Open Access  
CIRP Annals - Manufacturing Technology     Full-text available via subscription   (Followers: 10)
CIRP Journal of Manufacturing Science and Technology     Full-text available via subscription   (Followers: 13)
City, Culture and Society     Hybrid Journal   (Followers: 20)
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Clean Air Journal     Full-text available via subscription   (Followers: 2)
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Journal Cover Composites Science and Technology
  [SJR: 1.512]   [H-I: 144]   [159 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0266-3538
   Published by Elsevier Homepage  [3041 journals]
  • Roles of carbon nanotube and BaTiO3 nanofiber in the electrical,
           dielectric and piezoelectric properties of flexible nanocomposite
    • Abstract: Publication date: 26 May 2017
      Source:Composites Science and Technology, Volume 144
      Author(s): Jing Yan, Young Gyu Jeong
      We report the electrical, dielectric and piezoelectric properties of flexible PDMS-based nanocomposite generators, which are tunable by different contents of multi-walled carbon nanotube (MWCNT, 0.0–5.0 wt%) and BaTiO3 nanofiber (10–50 wt%). The BaTiO3 nanofiber with tetragonal structure was manufactured by an electrospinning and following calcination process. For the first series of nanocomposite generators with 30 wt% BaTiO3 nanofiber and 0.0–5.0 wt% MWCNT, both electrical and dielectric properties were dramatically enhanced at a critical MWCNT content of 0.47 wt% owing to the formation of percolating networks of MWCNT in the presence of BaTiO3 nanofibers, as verified by SEM analysis. Accordingly, the nanocomposite generator with 30 wt% BaTiO3 and 5.0 wt% MWCNT achieved the highest conductivity of 0.12 S/cm and dielectric constant of 4474 at 1 kHz, whereas the nanocomposite generator with 30 wt% BaTiO3 and 2.0 wt% MWCNT attained the best piezoelectric performance by harvesting average output voltage of ∼3.00 V, current of ∼0.82 μA, and power of ∼0.14 μW. In cases of the second series of nanocomposite generators with 2.0 wt% MWCNT and 10–50 wt% BaTiO3 nanofiber, the electrical conductivity and dielectric constant increased with the increment of BaTiO3 content up to 40 wt%. Overall, the nanocomposite generator with 2.0 wt% MWCNT and 40 wt% BaTiO3 nanofiber generated the highest average output voltage of ∼3.73 V, current of ∼1.37 μA, and power of ∼0.33 μW, which was feasible to light up commercial LEDs and to charge a capacitor after rectification, revealing the potentiality in powering self-sufficient nanodevices and wireless electronics.

      PubDate: 2017-03-20T13:08:49Z
  • Novel functional silica nanoparticles for rubber vulcanization and
    • Abstract: Publication date: 26 May 2017
      Source:Composites Science and Technology, Volume 144
      Author(s): Lijuan Chen, Zhixin Jia, Yuhan Tang, Lianghui Wu, Yuanfang Luo, Demin Jia
      A high reactive sulfocompound, sulfur monochloride, was chemically supported onto the surface of silica (silica-s-S2Cl2) by the reaction between chloric atom and silanol hydroxyl to obtain a novel vulcanizing agent, silica supported sulfur monochloride (silica-s-S2Cl2). Silica-s-S2Cl2 can be homogeneously dispersed in SBR matrix as a modifier and cure the styrene-butadiene rubber (SBR) without sulfur as a novel high-efficiency vulcanizing agent. The sulfur and Bis[3-(triethoxysilyl)propyl] Tetrasulfide (TESPT) silane coupling agent vulcanized SBR composites were mainly polysulfide crosslinks, on the contrary, the vulcanization by silica-s-S2Cl2 give priority to the mono- and disulfides crosslinks. The highlight of this work lies in the fact that apparent improvement has been achieved by novel and high efficient functional particles due to the silica surface supported with sulfur monochloride, which may open up new opportunities for the preparation of functional nano-fillers in rubber industry.

      PubDate: 2017-03-20T13:08:49Z
  • The mechanical behavior of CNT reinforced nanocomposites assuming
           imperfect interfacial bonding between matrix and nanoparticles and
           percolation of interphase regions
    • Abstract: Publication date: 26 May 2017
      Source:Composites Science and Technology, Volume 144
      Author(s): Yasser Zare, Kyong Yop Rhee
      The effective inverse aspect ratio (αeff) and volume fraction ( φ e f f ) of nanoparticles in polymer/CNT nanocomposites are defined accounting imperfect interfacial adhesion between polymer matrix and nanoparticles and percolation of interfacial regions as interphase percolation. After that, the tensile modulus and strength of nanocomposites are expressed by Halpin-Tsai and Pukanszky models to show the effects of radius (R) and length (l) of nanoparticles as well as the interphase thickness (t) and interfacial shear strength (τ) on the mechanical properties of nanocomposites. The best levels of “αeff” and “ φ e f f ” are obtained by the thinnest and the longest nanotubes as well as the highest values of “t” and “τ” factors. The best relative modulus of 8 is calculated by R < 13 nm and l > 6500 nm, while the strength slightly improves by R < 17 nm. Likewise, the relative modulus of 9 is calculated at t > 20 nm and τ > 170 MPa, while the best relative strength of 4.5 is shown at the highest levels of t = 25 nm and τ = 300 MPa. Conclusively, the interphase properties further affect the mechanical properties of nanocomposites compared to material parameters.

      PubDate: 2017-03-20T13:08:49Z
  • Computational micromechanics of fiber kinking in unidirectional FRP under
           different environmental conditions
    • Abstract: Publication date: 26 May 2017
      Source:Composites Science and Technology, Volume 144
      Author(s): F. Naya, M. Herráez, C.S. Lopes, C. González, S. Van der Veen, F. Pons
      The determination of ply properties of Fiber Reinforced Polymers (FRP) for particular operational environmental conditions in aeronautical applications is mandatory in order to fulfill current industry stringent certification requirements. However, the traditional experimental approach requires massive investments of resources and time. From the behaviour obtained experimentally, constitutive equations including failure criteria are then devised to be used in the design of FRP structures. The ply longitudinal behaviour under compression is generally the most difficult to measure and characterize. In this work, an alternative coupled experimental-computational micromechanics approach is proposed to determine the longitudinal compression properties of unidirectional FRP plies under different environmental conditions. This methodology includes experimental characterization of matrix and fiber/matrix interface, combined with numerical simulations of realistic microstructures. The interface decohesion is simulated using cohesive-frictional interactions. A pressure dependent, elasto-plastic model that includes tensile damage is employed to capture the matrix nonlinear behaviour. The numerical predictions match the experimentally-obtained ply properties available in the literature in a remarkable way and suggest that virtual ply property characterization is a mature and reliable approach to conduct screening of materials.

      PubDate: 2017-03-20T13:08:49Z
  • High thermal conductivity and excellent electrical insulation performance
           in double-percolated three-phase polymer nanocomposites
    • Abstract: Publication date: 26 May 2017
      Source:Composites Science and Technology, Volume 144
      Author(s): Dong-Li Zhang, Jun-Wei Zha, Chao-Qun Li, Wei-Kang Li, Si-Jiao Wang, Yongqiang Wen, Zhi-Min Dang
      High voltage direct current (HVDC) cable is attracting more attention during power transmission due to its many advantages. However, the accumulation of space charge, poor breakdown strength and low thermal conductivity of cable insulation layer have been a long-standing obstacle to utilize the HVDC cable applications. Because boron nitride nanosheets (BNNSs) are increasingly demanded in high thermal conductivity insulation materials, herein we report a facile and easy way to prepare styrene-(ethylene-co-butylene)-styrene tri-block copolymer/polypropylene (SEBS/PP) blends filled with BNNSs based on the construction of thermal conductive networks with double-percolation process. The morphology, thermal, and electrical properties of the BNNSs/SEBS/PP nanocomposites were investigated. Scanning electron microscopy showed that the BNNSs were well dispersed in the SEBS phase at low loading of 3 phr. The analysis results on electrical properties illustrated that the direct current (DC) breakdown strength and space charge suppression were remarkably improved by the introduction of BNNSs. In addition, the thermal conductivity of SEBS/PP blends (0.42 W m−1 K−1) was increased to 1.38 W m−1 K−1 when doped with 3 phr BNNSs. This nanocomposites with enhanced thermal conductivity and electrical properties have great potential to be used as recyclable insulating materials for HVDC.

      PubDate: 2017-03-20T13:08:49Z
  • Mode II interlaminar fracture toughness of CF/EP composite containing
           microencapsulated healing resins
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Habibah Ghazali, Lin Ye, Ming Q. Zhang
      The effects of microcapsules containing healing resins on the Mode II interlaminar fracture toughness (G IIC) of carbon fibre/epoxy composite laminates were investigated using end-notched flexure (ENF) specimens. The results indicate that the Mode II interlaminar fracture toughness of the original CF/EP laminates was improved with the incorporation of a dual-component microencapsulated self-healant. It was observed that the microcapsules induced toughening via two mechanism: i) larger plastic deformation due to a thicker resin-rich interlaminar region and ii) microcapsules in tempering hackle formation. When subjected to healing after release of the microencapsulated resins, the dual-component healant provided the laminates with 63% healing efficiency in Mode II interlaminar fracture toughness. Observation of fracture surfaces using scanning electron microscopy also revealed that the healing efficiency varied directly with the concentration of healant and subsequently the formation of a dense interlaminar region after the original fracture.

      PubDate: 2017-03-20T13:08:49Z
  • One-pot two-step perfluoroalkylsilane functionalization of multi-walled
           carbon nanotubes for polyurethane-based composites
    • Abstract: Publication date: 3 May 2017
      Source:Composites Science and Technology, Volume 143
      Author(s): Shasha Li, Xiao Du, Caiying Hou, Xiaogang Hao, Jinlan Jia, Taotao Guan, Tingfa Yi, Guozhang Ma
      A facile approach has been developed to prepare perfluoroalkylsilane functionalized multi-walled carbon nanotubes (MWCNTs) with high grafting content through one-pot two-step reactions. In this process, hydroxyl derivatized MWCNTs (hydroxylized MWCNTs) were covalently functionalized with 3-aminopropyl triethoxysilane by silanisation reaction, and subsequently reacted with hexafluorobutyl acrylate or dodecafluoroheptyl acrylate by Micheal-addition reaction. SEM, FT-IR and TGA characterizations demonstrated that the perfluoroalkylsilane were covalently attached onto the surface of MWCNTs and the higher molecular weight of perfluoroalky acrylate yielded higher grafting content. The perfluoroalkylsilane functionalized MWCNTs showed improved dispersibility and strong interfacial adhesion in/with polyurethane matrix. An increase in the grafting content led to a decrease the crystallinity and hydrogen bonding in the PU composites. As a result, the composites showed increased elongation and unimproved tensile strength, but reduced storage modulus and loss factor. Meanwhile, the higher grafting content offered their composite with higher hydrophobicity, lower percolation threshold and more enhanced electronic conductivity.
      Graphical abstract image

      PubDate: 2017-03-16T14:12:11Z
  • Conductive carboxylated styrene butadiene rubber composites by
           incorporation of polypyrrole-wrapped halloysite nanotubes
    • Abstract: Publication date: 3 May 2017
      Source:Composites Science and Technology, Volume 143
      Author(s): Yongwang Liu, Mingxian Liu
      Polypyrrole-wrapped halloysite nanotubes (PPy@HNTs) are prepared by polymerization of pyrrole on the surfaces of HNTs. PPy@HNTs show improved dispersion ability and stability in water compared with pure PPy due to the increased zeta potential. The PPy@HNTs dispersions are compounded with carboxylated styrene-butadiene rubber (xSBR) latex to prepare conductive xSBR/PPy@HNTs composites. The morphology, conductive performance, mechanical properties, and swelling performance of the xSBR/PPy@HNTs composites are determined. PPy@HNTs can be uniformly dispersed in the rubber matrix and form a conductive network. The conductivity of the composites increases with the loading of PPy@HNTs. When the content of PPy@HNTs is 10%, the conductivity of the xSBR rubber increases to 1.82 × 10−4 s/m which is much higher than the corresponding xSBR/neat PPy composites (4.62 × 10−8 s/m). Also, the composites show significantly improved mechanical properties both in static and dynamic condition. The tensile strength, Young's modulus, and storage modulus of the composites are substantially higher than those of pure xSBR. The rigid filler networks effectively limit the mobility of rubber molecule chains, which leads to decreased water swelling capacity and crosslink density. The prepared high performance rubber composites with good conductivity show promising applications in many areas such as piezoresistive sensor.
      Graphical abstract image

      PubDate: 2017-03-16T14:12:11Z
  • Radiation shielding property of structural polymer composite: Continuous
           basalt fiber reinforced epoxy matrix composite containing erbium oxide
    • Abstract: Publication date: 3 May 2017
      Source:Composites Science and Technology, Volume 143
      Author(s): Ran Li, Yizhuo Gu, Gaolong Zhang, Zhongjia Yang, Min Li, Zuoguang Zhang
      For protecting human body and equipment against radiation in nuclear power industry, radiation medicine and aerospace exploration, advanced materials possessing good shielding capability, low density and high mechanical strength and modulus are in urgent demand. In this study, radiation protective basalt fiber (BF) reinforced epoxy matrix composite containing erbium oxide (Er2O3) particles was fabricated by prepreg-autoclave process, in order to make a novel mechanical/radiation shielding composite. For prepared unidirectional and quasi-isotropic BF/Er2O3 composite laminates, basalt fibers and Er2O3 particles distributed uniformly, and no obvious agglomeration of particles and defects were found. NaI(Tl) detector was used to test mass attenuation coefficient for evaluating X and gamma rays shielding performance at different photon energies ranging from 31 keV to 662 keV. The experimental results indicate that BF/Er2O3 composite shows good X and gamma rays shielding performance, and mass attenuation coefficient of BF/Er2O3 composite is much larger than that of aluminum in relatively low energy from 31 keV to 80 keV. The effect of prepreg stacking consequence on shielding performance was also discussed. In addition, to verify the applicability of classic “mixture role” on mass attenuation coefficient of anisotropic composites, theoretical mass attenuation coefficient at different photon energies was calculated using XCOM software based on the weight fraction and mass attenuation coefficient of each constituent element among BF/Er2O3 composite. It is found that there is maximum deviation of 10.3% between experimental and theoretical results. Thus, it is believed that the method is suitable for predicting shielding performance of continuous fiber reinforced composite materials. Considering the advantages in light weight and high mechanical property, the studied three-phase composite is promising for using in radiation shielding structure application.

      PubDate: 2017-03-16T14:12:11Z
  • Synergistic effects of AlB2 and fluorinated graphite on the mechanical and
           tribological properties of hybrid fabric composites
    • Abstract: Publication date: 3 May 2017
      Source:Composites Science and Technology, Volume 143
      Author(s): Mingming Yang, Zhaozhu Zhang, Junya Yuan, Fang Guo, Xuehu Men, Weimin Liu
      In present work, the dry sliding wear properties of hybrid PTFE/Nomex fabric/phenolic composite (hybrid fabric composite), filled with aluminum diboride (AlB2), fluorinated graphite (FGr), and simultaneously filled with above fillers were investigated using a pin-on-disc tribo-meter. The wear rate and friction coefficient of hybrid fabric composite reinforced by different fillers were determined. Besides, the effects of fillers on hardness, thermal stability, thermal conductivity of hybrid fabric composites were systemically studied. The results showed that 3 wt% AlB2 filled hybrid fabric composite exhibited excellent anti-wear properties. The optimal filler percentage was determined by changing the content of FGr from 2 to 8 wt% whereas AlB2 was kept constant at 3 wt%. Those results mainly attributed to the improved hardness, thermal stability and thermal conductivity of hybrid fabric composite. Furthermore, the transfer film formed on the counterpart pin surfaces was demonstrated to be efficient in enhancing the tribological properties of filler reinforced hybrid fabric composites. The worn surfaces of the hybrid fabric composites were studied by scanning electron microscopy (SEM) and the corresponding wear mechanisms were discussed based on the characterizations.

      PubDate: 2017-03-16T14:12:11Z
  • Pyrene-functionalized PAEKs prepared from C–H borylation and Suzuki
           coupling reactions for the dispersion of single-walled carbon nanotubes
    • Abstract: Publication date: 3 May 2017
      Source:Composites Science and Technology, Volume 143
      Author(s): Yongpeng Wang, Mengzhu Liu, Tao Liu, Dayong Lu, Yang Sun, Haibo Zhang, Zhenhua Jiang
      The distribution of pyrene-functionalized single-walled carbon nanotubes (f-SWCNTs) within PEEK was investigated. Poly(aryl ether ketone)s with various contents of pyrene (PAEK-Py) were synthesized through iridium-catalyzed C–H borylation followed by Suzuki coupling. PAEK-Pys were characterized using UV–Vis, 1H NMR and gel permeation chromatography. The polymers were then used for non-covalent functionalization of pristine single-walled carbon nanotubes (SWCNTs). The functionalization efficiency was assessed by measuring the SWCNT dispersibility in chloroform. The maximal dispersion effect of the SWCNTs was obtained with the optimized conditions. In the presence of PAEK-Py-10, the dispersibility was as high as 272 mg L−1, and the dispersions containing 1.25 mg mL−1 of PAEK-Py-10 were very stable for 24 h with no solid deposits observed after being centrifuged at 5000 rpm for 15 min. Finally, pristine single-walled carbon nanotubes (SWCNTs) and non-covalently functionalized single-walled carbon nanotubes (f-SWCNTs) were used to prepare poly(ether ether ketone) (PEEK) composites (SWCNT/PEEK and f-SWCNT/PEEK) via co-blending in solution. The SWCNTs in the f-SWCNT/PEEK composite were dispersed better than those in the SWCNT/PEEK composite. These results suggest that PAEK-Pys could be used as an excellent dispersant for subsequent preparation of PEEK/SWCNT composites.

      PubDate: 2017-03-16T14:12:11Z
  • Multi-scaled enhancement of damping property for carbon fiber reinforced
    • Abstract: Publication date: 3 May 2017
      Source:Composites Science and Technology, Volume 143
      Author(s): Yan Li, Shenming Cai, Xiaolei Huang
      In this paper, a multi-scaled methodology by using flax fibers and carbon nanotubes (CNTs) was proposed to enhance the damping property of carbon fiber reinforced epoxy composites. The damping property was measured by free vibration test and the strength and modulus were obtained by tensile and flexural tests. Effects of stacking sequences of flax fibers and the addition of CNTs on both the damping property and the mechanical properties of carbon fiber reinforced composites were investigated. Results clearly showed that the damping property of carbon fiber reinforced composites was improved greatly by laying flax fibers on the outmost layers of the composites. With the addition of CNTs, the damping property was further enhanced. Damping modification mechanisms by hybridization with flax fibers and addition of CNTs were analyzed with the aid of the scanning electronic microscopy (SEM) and theoretical analysis. Results showed that the improved damping property of the hybrid composites was due to the internal sliding friction inside the flax fibers caused by the unique multi-scaled microstructure of the fibers and the stick-slip action of CNTs.

      PubDate: 2017-03-16T14:12:11Z
  • Large reduction in electrical contact resistance of flexible carbon
           nanotube/silicone rubber composites by trifluoroacetic acid treatment
    • Abstract: Publication date: 3 May 2017
      Source:Composites Science and Technology, Volume 143
      Author(s): Sang-Eui Lee, Sang Soo Jee, Hyokeun Park, Sung-Hoon Park, Intaek Han, Soichiro Mizusaki
      We report a large reduction in contact resistance between stretchable carbon nanotube/silicone rubber composites and silver electrodes by a chemical surface treatment, accompanied by an enhancement in the electrical conductivity of the composites. The reactive solvent, trifluoroacetic acid, works for the purpose. In addition, the treatment makes a uniform etching in a micro level with little sacrifice in surface roughness of the nanocomposites. The electrical conductivity of 1.0 wt% nanotube composite was enhanced approximately two-fold and three-fold by ten- and thirty-second treatment, which was induced by the reduction in the contact resistance to one half of an original value. It is meaningful that our finding can be an approach to reduce the nanoparticle loading while keeping electrical conductivity in a high level, which can be crucial for securing flexibility or stretchability in a viewpoint that the elongation is inversely proportional to the conductive particle loading.

      PubDate: 2017-03-16T14:12:11Z
  • Translaminar fracture toughness of interply hybrid laminates under tensile
           and compressive loads
    • Abstract: Publication date: 3 May 2017
      Source:Composites Science and Technology, Volume 143
      Author(s): A. Ortega, P. Maimí, E.V. González, J.R. Sainz de Aja, F.M. de la Escalera, P. Cruz
      This paper presents an experimental study of the translaminar fracture toughness under tensile and compressive loads of interply hybrid polymer-matrix composite laminates. The studied laminates were obtained by combining two of three different reinforcements: woven carbon fabric, woven glass fabric and unidirectional carbon tape, manufactured using the Resin Transfer Molding (RTM) process. The resulting in-plane quasi-isotropic laminates were generated by changing each material location along the thickness.

      PubDate: 2017-03-09T01:25:46Z
  • Aligned discontinuous intermingled reclaimed/virgin carbon fibre
           composites for high performance and pseudo-ductile behaviour in
           interlaminated carbon-glass hybrids
    • Abstract: Publication date: 3 May 2017
      Source:Composites Science and Technology, Volume 143
      Author(s): Marco L. Longana, HaNa Yu, Meisam Jalavand, Michael R. Wisnom, Kevin D. Potter
      Highly aligned intermingled fibre composites are produced from reclaimed and virgin carbon fibres using the High Performance Discontinuous Fibre (HiPerDiF) method. The stiffness and strength characteristics of these materials are studied as a function of the reclaimed to virgin fibres ratio. Interlaminated hybrid composites with discontinuous carbon fibre preforms sandwiched between continuous glass fibres are designed to demonstrate pseudo-ductility and allow investigation of the effect of the mixing ratio of reclaimed and virgin carbon fibres on the nonlinear stress-strain curve shape. The pseudo-ductile behaviour is explained by adapting the Damage Mode Map to describe the failure process of interlaminated hybrid specimens with different low elongation material strength. It is concluded that the HiPerDiF method is a valuable platform to remanufacture reclaimed carbon fibres into a high performance and potentially economical value recycled composite material. The Damage Mode Maps can be used to optimise the pseudo-ductile response of the interlaminated hybrid material.

      PubDate: 2017-03-09T01:25:46Z
  • Self-healing green composites based on soy protein and microfibrillated
    • Abstract: Publication date: 3 May 2017
      Source:Composites Science and Technology, Volume 143
      Author(s): Joo Ran Kim, Anil N. Netravali
      Self-healing soy protein isolate-microfibrillated cellulose (MFC-SPI) composites that incorporated poly(d,l-lactide-co-glycolide) microcapsules containing SPI (SPI-PLGA-MCs) as the healing agent were developed. SPI-PLGA-MCs prepared using a green solvent, ethyl acetate, had a protein loading of over 50%. Self-healing MFC-SPI (10 wt%) composites containing SPI-PLGA-MCs (15 wt%) had Young's modulus of about 970 MPa and strength of over 15 MPa whereas neat SPI resin had Young's modulus of 326 MPa and strength of about 8 MPa. The significantly higher tensile properties of composites compared to neat SPI resin was due to the inherent high tensile properties of MFC and excellent hydrogen bonding with SPI resin. Self-healing mechanism, i.e., healing agent (SPI) bridging the fracture surfaces of the microcracks, was observed through SEM imaging. Composites with no SPI-PLGA-MCs showed no self-healing whereas self-healing SPI composites showed 27% healing efficiency after 24 h healing. The self-healing efficiency was noticeably lower than 48% obtained earlier for self-healing SPI resin using the same SPI-PLGA-MCs. This was because the self-healing mechanism occurs only for the SPI resin component and not for the MFC fibrils. Self-healing of green composites can extend their useful life and make it easier for them to replace conventional composites derived from petroleum.

      PubDate: 2017-03-09T01:25:46Z
  • Electrical response of a laminate with a delamination: modelling and
    • Abstract: Publication date: 3 May 2017
      Source:Composites Science and Technology, Volume 143
      Author(s): Michele Zappalorto, Francesco Panozzo, Paolo Andrea Carraro, Marino Quaresimin
      An analytical and experimental study is carried out on the electrical response of a laminate with a delamination. The present study represents a basis for the detection of delaminations in conductive laminates through electrical measurements. As an example of application, the case of a Double Cantilever Beam (DCB) specimen is considered, with the aim to calculate the electric potential of a point on the surface of the laminate, and its variation as a function of the delamination length, highlighting the most influencing parameters. The accuracy of the theoretical predictions is verified against a number of finite element analyses, showing an extremely satisfactory agreement. In addition to this, theoretical predictions are also validated by comparison with a bulk of experimental data coming from an ad-hoc campaign, as well as using data taken from the literature. In all cases a good agreement is found.

      PubDate: 2017-03-09T01:25:46Z
  • Flower-like polyaniline/graphene hybrids for high-performance
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Fuyou Ke, Yu Liu, Hongyao Xu, Yu Ma, Shanyi Guang, Fayin Zhang, Naibo Lin, Meidan Ye, Youhui Lin, Xiangyang Liu
      A novel flower-like polyaniline/graphene hybrid (PANI-ATRGO) is prepared by a one-pot synthesis and used as electrode materials for supercapacitors. The structure, formation mechanism and electrochemical properties of such unique architecture are systematically investigated by combining Fourier transform infrared spectroscopy, Ultraviolet–visible absorption spectroscopy, Raman spectroscope, X-ray diffraction and electrochemical techniques. The results suggest that “V-type” amino groups of ATRGO and supermolecular assembly between PANI chains play the key role in the formation of flower-like nanostructures. Compare to pristine PANI (487 F g−1 at 1 A g−1), PANI-ATRGO electrode materials exhibit a remarkable improvement of the specific capacitance (1510 F g−1 at 1 A g−1) for supercapacitor in addition to excellent rate capacity and long-term cycling stability. Moreover, it is found that flower-like PANI-ATRGO hybrids exhibit better electrochemical properties than the corresponding nanorod-array hybrids in our previous study. This reveals the significance of controlling the hierarchical structure of hybrid materials in the development of high-performance supercapacitor.

      PubDate: 2017-03-09T01:25:46Z
  • Surface initiated grafting of polymer chains on carbon nanotubes via
           one-step cycloaddition of diarylcarbene
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Zhen Hu, Qing Shao, Xirong Xu, Dayu Zhang, Yudong Huang
      In the present study, we report a direct and nondestructive method to functionalize carbon nanotubes (CNTs). Novel highly reactive diarylcarbene derivative is designed and synthesized. Different to previous approaches, this diarylcarbene contains atomic transfer radical polymerization (ATRP) initiator segments, which can serve as starting points for further polymer grafting. Then, the initiator segments are covalently bonded to the CNTs via one-step cycloaddition of diarylcarbene and the succeeding ATRP links polystyrene (PS) chains to the CNTs. In order to further verify the effectiveness of modification, we use the obtained CNTs (PS-fCNTs) as reinforcement to enhance PS films. By addition 0.5 wt% PS-fCNTs, the PS composite films reveal 79.3 and 85.2% increases in tensile strength and Young's modulus. The protocol is believed to offer alternate strategy to modify the CNTs and greatly expand the application field of CNTs in material science.

      PubDate: 2017-03-09T01:25:46Z
  • Predicting the visco-elastic properties of polystyrene/SIS composite
           blends using simple analytical micromechanics models
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): A.P. Unwin, P.J. Hine, I.M. Ward, O.A. Guseva, T. Schweizer, M. Fujita, E. Tanaka, A.A. Gusev
      This paper is concerned with the prediction of the viscoelastic properties of rubber filled polymer blends. The question asked was as follows. Can the temperature dependent viscoelastic properties of phase separated polymer blends be adequately predicted using only a rational two phase micromechanics based analytical model with no empirical fitting parameters? In particular can this be achieved using only a knowledge of the individual bulk phase properties and the blend microstructure, but without any further detailed polymer physics knowledge such as the presence of an interphase region or any additional nanoscale structures within the separated rubber phase with the properties different from those of the two bulk phases? Blends of a polystyrene matrix containing phase separated rubber inclusions (a polystyrene-polyisoprene-polystyrene triblock polymer (SIS)) were manufactured in a range of blend fractions (up to 20 vol % of the triblock co-polymer). Experimental measurements, for the storage modulus G′ and the loss tangent tanδ, of both the individual phases and the blends, were made using dynamic mechanical tests over a range of temperatures from −50 to +70 °C. Numerical predictions, of the same properties, were first obtained using the generalised self-consistent Christensen and Lo model which uses a simple representative volume element (RVE) of an isolated sphere of the minority rubber component in a surrounding sheath of polystyrene matrix embedded in a homogeneous effective medium. The agreement between the Christensen and Lo model and the experimental measurements, for G′ and tanδ, was found to be excellent for rubber contents up to 10%. For a 20% rubber content, an improved prediction was obtained by altering the RVE to include the observed effect of having a polystyrene central core in a number of the dispersed rubber zones at this rubber fraction, using the Hervé and Zaoui generalization of the Christensen and Lo model. Although conjoined (and therefore non-spherical) zones became more prevalent at the highest rubber content, use of the Tandon and Weng model showed that this shape anisotropy would not be expected to affect the viscoelastic properties.

      PubDate: 2017-03-09T01:25:46Z
  • Significant accelerated crystallization of long chain branched
           poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with high nucleation
           temperature under fast cooling rate
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Hengxue Xiang, Wei Chen, Ziye Chen, Bin Sun, Meifang Zhu
      The long chain branched poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (LCB-PHBV) with rapid crystallization rate and high nucleation temperature was fabricated by only adding small amounts of dicumyl peroxide (DCP). NMR and FTIR spectra confirmed that long chain branched structures of LCB-PHBV were formed in the melting reaction process. The results from non-isothermal crystallization indicated that crystallization rate and crystallinity of LCB-PHBV presented an obvious increase while half crystallization time decreased obviously. Interestingly, during melting crystallization, the crystallization rate of LCB-PHBV increased with the increase of cooling rate and curves of crystallization peaks shifted obviously to higher temperatures. Based on polarized optical microscopy observation, it was found that the nucleation abilities of LCB-PHBV under a higher temperature had been improved, whereas the diffusion of molecular chains inhibited the radial growth of spherulites. However, such contribution of nucleation promoting effect on crystallization of polymers was larger than dispersion inhibition effect of segments, resulting in an inducement and acceleration on crystallization process of LCB-PHBV.

      PubDate: 2017-03-03T11:30:48Z
  • New insight on the interfacial interaction between multiwalled carbon
           nanotubes and elastomers
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Nanying Ning, Dongliang Cheng, Jianhua Yang, Li Liu, Ming Tian, Youping Wu, Wencai Wang, Liqun Zhang, Yonglai Lu
      We studied the effect of the microstructure of multiwalled carbon nanotubes (MWCNTs) on interfacial interaction in seven kinds of MWCNT/natural rubber (NR) composites. Unexpectedly, the degree of defects (ID/IG) of MWCNTs was found to play a key role in the interfacial interaction of MWCNT/NR composites. The content of bound rubber (BR) of the composites almost linearly increased with the increase in the ID/IG of MWCNTs. Then we studied the interfacial interaction between MWCNTs with high degree of defects and NR. Interestingly, the BR of the composites consisted of loosely adsorbed BR (LBR) and tight BR (TBR). TBR occupied about half of the total BR, and cannot be removed by extraction in hot toluene for 48 h. Meanwhile, the mobilities of macromolecules in TBR were more restricted than those in LBR. We discussed in depth the molecular origin of the interfacial interaction between defected MWCNTs and NR, and then proposed that LBR was topologically confined by the steps-like structure of defected MWCNTs whereas TBR was principally chemically bonded to MWCNTs. This study provided new insight on the interfacial interaction between MWCNTs and NR and thus provides guidance for the preparation of high-performance elastomer composites with strong interfacial interaction.
      Graphical abstract image

      PubDate: 2017-03-03T11:30:48Z
  • Optimal configuration of magnetoelectric composites under various
           mechanical boundary conditions
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Kyung Ho Sun, Jae Eun Kim, Byeong Ock Kim, Yoon Young Kim
      The magnetoelectric (ME) coupling effect of magneto-electro-elastic composites is generated by the product property of magnetostriction and piezoelectricity via elastic deformation. Since mechanical deformation and interlayer stress interaction directly influence the extrinsic ME effect, composite configurations between magnetostrictive and piezoelectric materials critically influence the energy conversion efficiency of ME composites, as also do the imposed mechanical boundary conditions (BCs). Here, we aim to identify the material configurations in the composites under different BCs, in order to maximize their ME effects. The problem is set up as optimization problems solved by a genetic algorithm while the required multiphysics simulation is performed by finite element analysis. For five major mechanical BCs, we determined optimal ME laminate layer configurations and compared their magneto-electric conversion efficiency with that by typical sandwiched laminate composites. We also investigated how much the efficiency can be increased if arbitrary-arranged material distributions are allowed. The present study is expected to provide useful guidelines for the design of ME composites, and offers the possibility of finding new ME composite structures.

      PubDate: 2017-03-03T11:30:48Z
  • Network structure and mechanical properties of polydimethylsiloxane filled
           with nanodiamond – Effect of degree of silanization of nanodiamond
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Faezeh Hajiali, Akbar Shojaei
      Reinforcement of polydimethylsiloxane (PDMS) was investigated using untreated nanodiamond (uND) and silane functionalized ND (sND) at various degrees of silanization. Scanning electron microscopy revealed an improved dispersion of ND in PDMS by silanization. The incorporation of uND and sNDs enhanced tensile strength up to 45% and 70%, respectively; however, greater improvement was observed for sNDs at very low concentrations, e.g. 0.2 wt%. The much improvement in crosslinking density, analyzed by Flory-Rehner model and Mooney-Rivlin plot, and interfacial interaction, characterized by Kraus and Cunneen-Russell plots, was also observed for sNDs. Interestingly, it was found that the extent of improvement in all the properties was closely related to the degree of silanization of sND. Dynamic mechanical properties of PDMS/ND composites were also investigated and discussed accordingly.

      PubDate: 2017-03-03T11:30:48Z
  • Nonlinear vibration and postbuckling of functionally graded graphene
           reinforced porous nanocomposite beams
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Da Chen, Jie Yang, Sritawat Kitipornchai
      The nonlinear free vibration and postbuckling behaviors of multilayer functionally graded (FG) porous nanocomposite beams that are made of metal foams reinforced by graphene platelets (GPLs) are investigated in this paper. The internal pores and GPL nanofillers are uniformly dispersed within each layer but both porosity coefficient and GPL weight fraction change from layer to layer, resulting in position-dependent elastic moduli, mass density and Poisson's ratio along the beam thickness. The mechanical property of closed-cell cellular solids is employed to obtain the relationship between coefficients of porosity and mass density. The effective material properties of the nanocomposite are determined based on the Halpin-Tsai micromechanics model for Young's modulus and the rule of mixture for mass density and Poisson's ratio. Timoshenko beam theory and von Kármán type nonlinearity are used to establish the differential governing equations that are solved by Ritz method and a direct iterative algorithm to obtain the nonlinear vibration frequencies and postbuckling equilibrium paths of the beams with different end supports. Special attention is given to the effects of varying porosity coefficients and GPL's weight fraction, dispersion pattern, geometry and size on the nonlinear behavior of the porous nanocomposite beam. It is found that the addition of a small amount of GPLs can remarkably reinforce the stiffness of the beam, and its nonlinear vibration and postbuckling performance is significantly influenced by the distribution patterns of both internal pores and GPL nanofillers.

      PubDate: 2017-03-03T11:30:48Z
  • In situ construction of pompon-like hydroxyapatite hybrid via interfacial
           self-assembly in polypropylene matrix
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Xuewei He, Wei Xu, Yuansen Liu, Min Nie, Qi Wang
      This work reports on a one-pot in situ epitaxial growth strategy to prepare a pompon-like hydroxyapatite (HA) hybrid that demonstrates a good interfacial interaction by mechanical interlocking with polypropylene (PP) melts, resulting in improved mechanical performance. The formation process involves the preferred adsorption of dissolved WBG molecules (a rare earth compound) at the polydopamine-modified HA particle–polymer melt interface, followed by in situ epitaxial growth of the thorn-like branches. The branch size and density depend on the nucleation and diffusion of the WBG molecules, and can be adjusted by the heating temperature, cooling rate, WBG concentration, etc. The concept that the mechanical interlocking of pompon-like WBG–HA hybridized with a PP matrix can improve the interfacial interaction was successfully realized, as indicated by the mechanical performance of PP/HA composites with pompon-like structures outperforming the conventional PP/HA composites up to an increase of 45% in impact strength.

      PubDate: 2017-03-03T11:30:48Z
  • Fabrication and characterization of HMX@TPEE energetic microspheres with
           reduced sensitivity and superior toughness properties
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Yubin Li, Zhijian Yang, Jianhu Zhang, Liping Pan, Ling Ding, Xin Tian, Xue Zheng, Feiyan Gong
      The development of a facile method for improvement of interface interaction between rigid particles and coating polymer is of great importance for energetic composite materials, especially for military purpose. In this paper, energetic composites with spherical morphology, toughness property and low sensitivity are firstly fabricated by using Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) as core material and thermoplastic polyester-ether elastomer (TPEE) as shell material via an emulsion solvent evaporation (ESV) method. From the morphology and structure characteristic of as-prepared energetic microspheres, it is found that the HMX@TPEE energetic microspheres have uniform spherical morphologies, narrow size distribution and honeycomb coating structure under the circumstance of compound emulsifiers and appropriate core-shell ratio. The good toughness of HMX@TPEE microspheres in Brazilian test and dynamic mechanical analysis (DMA) demonstrates a new route to enhance interface interaction between HMX particles and TPEE matrix. Moreover, because of the favorable energy-decentralizing property of this exotic honeycomb structure, the sensitivity of HMX@TPEE microspheres measured by BAM impact sensitivity instrument can be markedly decreased and the impact energy ( E li ) can be improved from 3.5 J to 8.0 J at the HMX/TPEE ratio of 5/1. This fabrication of HMX@TPEE microspheres with adjustable coating content via a facile ESV process might provide a promising approach for HMX based energetic composites to enhance the safety and toughness properties when used in advanced weapon system.

      PubDate: 2017-03-03T11:30:48Z
  • Detecting impact traces on a composite pressure vessel with
           aluminum-coating optical fiber using a phase-modulated BOCDA sensor
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Bo-Hun Choi, Dae-Cheol Seo, Il-Bum Kwon
      Impact traces on a composite pressure vessel were detected by measuring residual strain in aluminum (Al)-coating optical fiber for the first time. The residual strain was obtained by a Brillouin optical correlation domain analysis (BOCDA) sensor system, where a continuous optical signal was simultaneously phase-modulated to choose the sensing position, and single-side-band modulated to find the Brillouin frequency. This sensor system successfully measured the Brillouin frequency, which can be converted to the strain, along a 500 m long optical fiber, with distance resolution of less than 1.5 cm. The cantilever beam test using a bonded optical fiber presented the strain conversion coefficient, which was determined by the comparison between the measured Brillouin frequency and the strain of an electric strain gauge. Al-coating optical fiber was attached around the surface of a composite pressure vessel, and consecutive impacts at six separate positions were applied using hemisphere and wedge impactors with energies of 10, 20, and 40 J. The measured Brillouin frequencies were the unchanged intrinsic frequency along the whole fiber length, except for the six peak positions, which exactly coincided with the impact positions. The fine measurement at these peak positions showed the frequency peaks to be composed of two split peaks, which were compared with photographs taken while the impacted surfaces were deformed. This confirmed that a dent temporarily formed at an impact position caused the optical fiber to bend twice, and the strain remained at two adjacent positions. Hydraulic pressure test of the composite pressure vessel after the impacts showed that this measurement system could detect small impact traces that do not cause critical structural degradation, as well as large impact damages.

      PubDate: 2017-03-03T11:30:48Z
  • A long-term mechanical degradation model of unidirectional natural fiber
           reinforced composites under hydrothermal ageing
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Fang Tian, Yihui Pan, Zheng Zhong
      In this paper, a constitutive model is developed for unidirectional natural fiber reinforced composite materials to describe their mechanical degradations when subjected to long-term hydrothermal ageing. Two internal variables, which reflect the effects of moisture absorption and hydrolysis reaction, are incorporated into the Helmholtz free energy and energy dissipations within non-equilibrium thermodynamic framework. Furthermore, specific forms of modified Helmholtz free energy are employed to study the constitutive behaviors of the composite and the damage evolution laws for hydrothermal ageing processes are established. We then apply the theoretical model to analyze elastic responses of the composite under long-term hydrothermal ageing. The present theoretical predictions are found in agreement with the existing experimental results, which shows that the moisture absorption related damage develops rapidly and reaches a plateau within 20 days, resulting in a sharp decrease of elastic modulus of the composite at the early ageing stage, whereas the evolution of deterioration associated with hydrolysis reaction is at a much slower rate.

      PubDate: 2017-02-23T16:51:38Z
  • Fabrication and testing of composite orthogrid sandwich cylinder
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Shu Jiang, Fangfang Sun, Hualin Fan, Daining Fang
      To get a strong, stiff and weight efficient cylindrical shell, a carbon fiber reinforced orthogrid-core sandwich cylinder was designed and fabricated. The core is made up of orthogonal grids and manufactured by interlocking method. The sandwich cylinder is fabricated by filament winding method. Free vibration test combining with theoretical analysis and numerical simulation was carried out to reveal the vibration responses and estimate the modulus of the wound laminate. Uniaxial compression test was performed to reveal the strength and failure mode. Without end flanges, laminate delamination at the end controls the peak load. Delamination of skins induces interfacial debonding and dimpling of inner skin finally. An engineering method based on the average strain at the peak load is proposed to predict the load capacity of the cylinder. Compared with stiffened cylinder, the orthogrid sandwich cylinder is stiffer and stronger. Meanwhile, its making process is simplified and the mechanical ability is comparable with other lattice-core sandwich cylinders.

      PubDate: 2017-02-23T16:51:38Z
  • Fully degradable PLA-based composite reinforced with 2D-braided Mg wires
           for orthopedic implants
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Xuan Li, Chenglin Chu, Li Zhou, Jing Bai, Chao Guo, Feng Xue, Pinghua Lin, Paul K. Chu
      Fully degradable poly-lactic acid (PLA) is reinforced with 2D-braided magnesium alloy wires (Mg wires or MAWs) for bone fixation devices. The relationship between the mechanical/degradation properties of the composite and microstructural features such as braiding angle, volume fraction, and interface properties is investigated. The biaxial mechanical properties of the composite can be tailored by the microstructure. When the braiding angle is 45°, the composite has the highest shear and impact strength and increasing the volume fraction simultaneously improves the tensile, bending, shear, and impact strength. Results obtained by the finite element method show that the screw hole undermines the safety factor of the composite under micro-strain. Acidic degradation of pure PLA can be mitigated by the corporation of MAWs and a degradation model is proposed to predict the mechanical properties of the composite during immersion. Our results reveal a relationship between the bending strength, molecular weight, and immersion time.

      PubDate: 2017-02-23T16:51:38Z
  • In situ fabrication of copper electrodes on carbon-fiber-reinforced
           polymer (CFRP) for damage monitoring by printing and flash light sintering
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Sung-Jun Joo, Myeong-Hyeon Yu, Eun-Beom Jeon, Hak-Sung Kim
      The electrical resistance change method (ERCM) is a promising method for structural health monitoring (SHM) of composites. In this work, copper (Cu) nano-ink was printed and successfully sintered on carbon-fiber-reinforced polymer (CFRP) substrate for damage sensing via a flash light sintering method. Before printing, surface-polished CFRP substrate was flash light treated to remove remnant epoxy between carbon fibers. Then, Cu nano-ink was formulated and printed on the CFRP substrate, and the printed Cu nano-ink patterns were sintered within a few milliseconds using a range of flash light irradiation energies. A two-step flash light sintering method to reduce contact resistance between the Cu electrode and CFRP interface was further investigated. Fabricated Cu electrodes were characterized using scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). Using a two-step sintering approach, we fabricated Cu electrodes on CFRP with low contact resistance (0.93 Ω), high durability, and no mechanical degradation of CFRP substrate.

      PubDate: 2017-02-23T16:51:38Z
  • Facile synthesis of imidazole microcapsules via thiol-click chemistry and
           their application as thermally latent curing agent for epoxy resins
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Chunmei Li, Jiaojun Tan, Junwei Gu, Ying Xue, Lei Qiao, Qiuyu Zhang
      A novel method was developed to encapsulate 1-benzyl-2-methylimidazole (1B2MZ) to produce microcapsule-type latent curing agent using thiol-click reaction in an oil/water emulsion. The fabrication process was significantly simplified and required reaction time was greatly shortened due to the efficiency of click chemistry. In the oil phase, 1B2MZ was mixed with reactive monomers, 1,3,5-tri-2-propenyl-1,3,5-triazine-2,4,6 (1H, 3H, 5H)-trione (TTT) and tris[2-(3-mercaptopropionyloxy)ethyl] isocyanurate (TEMPIC) which would polymerize to result in polythioether shell of microcapsules by following a photoinitiated thiol-ene mechanism. Polyvinyl alcohol (PVA) aqueous solution acted as water phase. The whole reaction process lasted for 20 min, which was enough for almost full conversions of monomers. The generated latent curing agent had good spherical shapes with smooth outer surfaces and the mean diameter distributed in the range of 105.7 to 18.17 μm by adjusting PVA concentration or viscosity of oil phase. The curing behavior, kinetics and releasing mechanism of latent curing agent were studied by differential scanning calorimetry (DSC) and scanning electron microscope (SEM). This microcapsule-type latent curing agent had a long storage life for 30 days when mixed with epoxy resin at 20 °C, and the mixture could be cured at 100 °C within 1 h.

      PubDate: 2017-02-23T16:51:38Z
  • Imparting low dielectric constant and high modulus to polyimides via
           synergy between coupled silsesquioxanes and crown ethers
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Chuqi Shi, Shumei Liu, Yang Li, Yanchao Yuan, Jianqing Zhao, Yi Fu
      Our pilot research revealed that the dielectric constant of polyimide (PI) can be reduced and the modulus can be improved by assembling necklace-like interlocking complexes with crown ethers. Not only did we find that these properties of the PI complex still cannot adequately meet the demand of practical applications but also that there was a deterioration in its thermal stability. A functional octa(aminopropyl)silsesquioxane (OAPrS) with a significantly rigid Si-O-Si cage was incorporated into an 18-crown-6 (CE6)-PI (CE6-PI) complex to produce inorganic-organic OAPrS/CE6-PI nanocomposites. By exploiting the synergetic effect of OAPrS and CE6, most properties of the PI were clearly improved. In the case of 3.9 wt% OAPrS and 7.8 wt% CE6, the dielectric constant of PI was reduced by 30%, and Young's modulus and the tensile strength were increased by 106% and 23%, respectively. In addition, the thermal stability of the CE6-PI complex was modified, and its 5% weight loss temperature and glass transition temperature were increased by 31.2 and 11.2 °C, respectively, with the incorporation of 3.9 wt% OAPrS. The indispensable nano-reinforcing role of aggregated OAPrS crystal in the nanocomposite was carefully analysed and verified.

      PubDate: 2017-02-17T06:05:04Z
  • Microscale based prediction of matrix crack initiation in UD composite
           plies subjected to multiaxial fatigue for all stress ratios and load
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): R.D.B. Sevenois, D. Garoz, F.A. Gilabert, S.W.F. Spronk, W. Van Paepegem
      A criterion is developed which predicts matrix fatigue crack initiation for Uni-Directional (UD) composite plies subjected to multiaxial fatigue load at all stress-ratio's: Tension-Tension, Compression-Compression and Tension-Compression. This research is based on physical observations of matrix damage types and their respective driving forces. Existing fatigue prediction formulations, that partly succeed in predicting fatigue life to initiation, are investigated for their key attributes which are subsequently combined in a coherent way. The framework requires 7 material parameters: 4 for Tension-Tension load, 2 for Compression-Compression load and 1 to take into account the accelerated occurrence of damage under Tension-Compression load. The material parameters can be calibrated from only 7 crack initiation S-N curves. 5 experimental datasets, a variety of the two most common reinforcing fibres and matrix (Carbon and Glass fibres combined with an epoxy or PEEK resin), are selected for a thorough verification and validation of the criterion. The agreement of the prediction with experiment is, remarkably, excellent for Glass/Epoxy, good for Carbon/Epoxy and reasonable for Carbon/PEEK. This new framework establishes a solid base for further developments to predict matrix crack initiation and the inclusion of other failure types such as fibre kinking.

      PubDate: 2017-02-17T06:05:04Z
  • Poly(methyl methacrylate)/boron nitride nanocomposites with enhanced
           energy density as high temperature dielectrics
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Feihua Liu, Qi Li, Zeyu Li, Yang Liu, Lijie Dong, Chuanxi Xiong, Qing Wang
      The development of advanced dielectric materials with high electric energy densities at elevated temperatures is of crucial importance in modern electronics and electric power systems. Herein, poly(methyl methacrylate) (PMMA)/boron nitride nanosheets (BNNS) nanocomposites for high temperature applications were prepared using a facile solution cast method. It was found the incorporation of BNNS into PMMA increased the thermal conductivity and enhanced the capacitive properties of the nanocomposites. A discharged energy density that is over 210% that of the state-of-the-art biaxially oriented polypropylene (BOPP) and a charge-discharge efficiency of more than 97% have been achieved in PMMA/BNNS under an electric field of 200 MV/m at 70 °C. The incorporation of uniformly dispersed nanosheets into polymer matrix as charge-blocking barrier paves a way to significant reduction of conduction loss in high temperature dielectrics.

      PubDate: 2017-02-17T06:05:04Z
  • Processing, characterisation and electromechanical behaviour of
           elastomeric multiwall carbon nanotubes-poly (glycerol sebacate)
           nanocomposites for piezoresistive sensors applications
    • Abstract: Publication date: Available online 16 February 2017
      Source:Composites Science and Technology
      Author(s): Yi Yan, Vitor Sencadas, Jiangshan Zhang, Guoqing Zu, Dongbin Wei, Zhengyi Jiang
      Highly stretchable elastomeric multiwall carbon nanotubes – poly (glycerol sebacate) (MWCNT-PGS) nanocomposites were prepared by mixing conductive multiwall carbon nanotubes (MWCNTs) with PGS prepolymer and curing at 120 °C. The incorporation of conductive filler increases the matrix crosslinking density and mechanical stiffness without loss of the flexibility and elasticity of the polymeric network with low mechanical hysteresis behaviour. The percolation threshold for the electrical conductivity was found to be ∼1 wt.% of MWCNTs. The piezoresistive behaviour of the prepared samples shows a negative gauge factor (GF) between -0.5 and -0.8 under uniaxial tensile stress, probably due to geometrical factors, whilst under 3-point bending the calculated GF values were positive and a maximum GF = 42 was achieved for the samples with 2 wt.% MWCNTs. Overall, the unique property combination between the MWCNTs and the PGS make them potentially suitable for the development of large deformation piezoresistive sensors, especially for biomedical engineering applications, flexible and wearable devices.

      PubDate: 2017-02-17T06:05:04Z
  • Modelling delamination migration in angle-ply laminates
    • Abstract: Publication date: Available online 16 February 2017
      Source:Composites Science and Technology
      Author(s): B.Y. Chen, T.E. Tay, S.T. Pinho, V.B.C. Tan
      This paper presents a numerical study of the delamination migration in angle-ply laminates observed in experiments reported in the literature, where the delamination originally propagates along the lower, 0 ∘ / 60 ∘ interface and later migrates onto the upper, 60 ∘ / 0 ∘ interface. The recently-developed Floating Node Method (FNM) is used for modelling this problem. The initiation and propagation of both delamination and matrix cracks are modelled within the FNM elements. Experimentally-observed phenomena such as the numerous kinking attempts and the multiple onset locations of migration are successfully predicted. The effect of load offset on the locations of migration is captured. In addition, this work tries to shed light on the proper use of standard cohesive elements in cases where delamination migration is expected.

      PubDate: 2017-02-17T06:05:04Z
  • Mechanical and electrical behavior of rubber nanocomposites under static
           and cyclic strain
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Jin-Yong Lee, Vineet Kumar, Xiao-Wu Tang, Dong-Joo Lee
      Rubber nanocomposites based on carbon nanotubes (CNT), graphitic nanofiller (GR), and their hybrid (CNT+GR) were studied under static and cyclic strain for robotics applications. Room temperature vulcanized (RTV) silicone rubber was used as a matrix for the nanocomposites, which were prepared by solution mixing. The specimens based on CNT show a better modulus of 1.77 MPa than GR (0.71 MPa) and CNT+GR hybrid (0.85 MPa) specimens. The resistance was 0.27 kΩ (CNT) and 30.48 kΩ (CNT+GR hybrid) at 10% strain and increased to 0.35 kΩ and 46.49 kΩ at 100% strain. During cyclic strain (30%) tests, the CNT-based specimen shows larger hysteresis losses (slope m = -0.179) as dissipated heat than the GR (m = −0.032) and CNT+GR hybrid (m = -0.096) specimens. The specimens were tested as electrode materials in an actuator, and higher displacements of 1.992 mm (CNT), 1.489 mm (CNT+GR hybrid), and 0.075 mm (GR) were achieved at 10 kV (3 phr). Such improvements could be useful in intelligent objects as artificial muscles or electro-active locomotive parts.

      PubDate: 2017-02-11T01:32:20Z
  • Influence of chain mobility on rheological, dielectric and electromagnetic
           interference shielding properties of poly methyl-methacrylate composites
           filled with graphene and carbon nanotube
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Seyed Esmaeil Zakiyan, Hamed Azizi, Ismaeil Ghasemi
      Rheological, dielectric and electromagnetic interference shielding (EMI) properties of multi-walled carbon nanotube (MWCNT) and graphene nano-pellets (GNP) poly(methyl methacrylate) (PMMA) composites were compared. The GNP readily formed a polymer-mediated filler network compared to MWCNT, as evidenced by rheological tests. Immobilization of the interphase region was higher under the influence of the GNP in comparison with the MWCNT. However, the MWCNT-filled samples showed superior dielectric properties in respect to the GNP-filled samples. Particle shape and polymer chain dynamics in the interphase affected the dielectric properties. It was hypothesized that intensive immobilization, resulted from the GNP network, reduced free volume for segmental chain movements and dipole orientation along the applied electric field; which caused a decrease in dielectric permittivity. The MWCNT-filled samples were more efficient in electromagnetic wave absorption and reflection in comparison with the GNP-added samples which is ascribed to the one-dimensional geometry of nanotube aggregates and better tendency to form a conductive network with direct filler–filler contacts.

      PubDate: 2017-02-11T01:32:20Z
  • Experimental characterization of the interlaminar fracture toughness of a
           woven and a unidirectional carbon/epoxy composite
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): D. Fanteria, L. Lazzeri, E. Panettieri, U. Mariani, M. Rigamonti
      An experimental program has been carried out at the University of Pisa, in collaboration with Leonardo Helicopter Division, to investigate the differences in interlaminar fracture toughness properties of a graphite/epoxy composite material, available in two forms: unidirectional tape and five harness satin fabric. To this end, tests have been carried out in mode I, mode II and mixed I + II mode on specimens manufactured with the two material systems by Leonardo HD, following their industrial standards. The results show a considerably higher toughness of the fabric, as a consequence of the peculiar features at the delamination interface and of the other local mechanisms, capable of absorbing energy, that are present only in fabric composites. Some fractographic observations confirm these mechanisms. Finally, numerical analyses have been carried out, modelling with Finite Element the various tests, to complement and evaluate the data reduction methods used to derive the toughness values.

      PubDate: 2017-02-11T01:32:20Z
  • A new analytical solution for spring-in of curved composite parts
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Anxin Ding, Shuxin Li, Jihui Wang, Aiqing Ni
      A new analytical solution considering three dimensional effects on spring-in of curved composite parts has been proposed based on modification of the model presented by Wisnom et al. [28]. In the new analytical solution the composite part is assumed in generalized plane strain condition between gelation and vitrification rather than in plane stress condition as proposed by Wisnom et al. [28]. The material properties are assumed to present a step change in the vitrification point with constant values in each state. Consequently the new solution not only considers the effect of the cure process generated strain in the rubbery state in the through-thickness direction but also the strain in the length direction for prediction of the cure-induced spring-in of curved composites parts. The proposed new analytical solution is verified by the good agreement between the experimentally measured spring-in angels presented by previous studies and analytically predicted results presented by author for both the unidirectional and cross-ply C-sections composite parts. Further investigation by numerical analysis also provides a favourable comparison with experimental findings and analytical results.

      PubDate: 2017-02-11T01:32:20Z
  • Design and fabrication of morphologically controlled carbon
           nanotube/polyamide-6-based composites as electrically insulating materials
           having enhanced thermal conductivity and elastic modulus
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Takuya Morishita, Yoshihide Katagiri, Takuro Matsunaga, Yoshimi Muraoka, Kenzo Fukumori
      Electrically insulating polymer materials having high thermal conductivity and elastic modulus are in high demand for next-generation electric machines and electronic devices. Carbon nanotubes (CNTs) show extremely high thermal conductivity and elastic modulus; however, even the addition of a few CNTs to polymers leads to them losing their electrically insulating properties. Herein, morphologically controlled multiwalled CNT (MWCNT)/polyamide-6 (PA6)/poly(p-phenylene sulfide) (PPS) composites, having high thermal conductivity, electrical insulation and elastic modulus, were designed and fabricated. First, MWCNT/PA6/PPS/EGMA composites comprising a PA6 matrix and MWCNT-localized PPS domains surrounded by shell-layers formed from poly(ethylene-co-glycidyl methacrylate) (EGMA) were prepared. The thermal conductivity of the composites was improved without losing the volume resistivity. However, these composites showed low elastic modulus, especially at high temperature, due to MWCNT localization and the existence of EGMA. Therefore, MWCNT/PA6/PPS/(3-glycidyloxypropyl)trimethoxysilane (GOPTS) composites having a novel morphology were designed and fabricated using GOPTS as a highly reactive shell-forming agent. In this composite, the MWCNT ends were capped with nano-sized PPS domains (MWCNT-PPS nanodomain-linked structure) to prevent electrically conductive paths forming, and MWCNT-PPS nanodomain-linked structures were uniformly dispersed in the PA6 matrix, leading to much enhanced elastic modulus and heat resistance in addition to improved thermal conductivity and electrically insulating properties. These composites containing CNT-nanodomain-linked structures are promising as electrically insulating materials for various applications including high-performance electric machines and electronic devices.

      PubDate: 2017-02-11T01:32:20Z
  • Relative planar strain control and minimizing deformation work in
           elastomeric sheets via reinforcing fiber arrays
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Michael Krieg, Kamran Mohseni
      This study investigates soft composite sheets that undergo significant deformations. The fiber reinforcement in these systems not only increases the stiffness of sheets like a traditional composite, but also controls the relationships between strains in orthogonal planar directions. Such an ability is useful in controlling the deformation of soft robots, and also enhancing the output of soft actuation techniques like electro-active polymer actuators (also called dielectric actuators). The inspiration for this work comes from squid mantle structures that couple orthogonal components of strain using helical fiber reinforcement. The resulting null space of deformations corresponding to the fiber restrictions creates a family of body deformations that optimize propulsion. The strain dynamics in the composite sheet are modeled geometrically from fiber orientations, assuming that the fibers are inextensible. After the strain dynamics have been determined, the stress/strain relationship is modeled by considering the matrix and reinforcing fibers to be two separate homogeneous systems interacting through local stresses. Both steps of this modeling technique are validated experimentally showing planar strains in a preferred direction to be as high as 16 times the resulting planar strain of an equivalent unreinforced sheet by forcing negative strains in the orthogonal planar directions. The work required for deformation is derived from the stress/strain relationship by calculating the strain energy stored in the material, and an optimal balance between increased planar strain output and increased material stiffness is analyzed. It is shown that for the specific materials used to create the soft composite sheets (thermoplastic elastomer with cotton fibers) optimal fiber angles lie between 15° and 25° to minimize work required for deformation, but this optimal range will increase with increasing ratio of fiber to matrix modulus.

      PubDate: 2017-02-11T01:32:20Z
  • Piezoelectric BaTiO3/alginate spherical composite beads for energy
           harvesting and self-powered wearable flexion sensor
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Nagamalleswara Rao Alluri, Sophia Selvarajan, Arunkumar Chandrasekhar, Balasubramaniam Saravanakumar, Ji Hyun Jeong, Sang-Jae Kim
      A simple, large-scale fabrication of spherical composite (BaTiO3 nanoparticle/Ca-alginate) beads was developed using the ionotropic gelation (IG) method. The energy harvesting performance of a composite bead-based nanogenerator (CBNG) was studied using various device areas (3 cm2, 11.25 cm2), different mechanical pressures (170 Pa–1.77 kPa) and bending angles, rapid hand force, capacitive loadings and electrical poling. High output (82 V, 227 μA) was generated with a simple low mechanical pressure of 1.70 kPa, which is enough to drive low power electronic devices. We demonstrate that the strip-based CBNG (S-CBNG) device can act as a self-powered wearable flexion sensor for decoding right arm finger flexion/extension movements in a periodic manner without any external battery and additional sensory circuit. It is highly desirable to classify and detect finger movements for in-patient rehabilitation, finger Braille typing and directional bending of the human body. In this work, the average peak power of the flexible S-CBNG varied from 1.23 pW to 0.4 nW for flexion/extension movements of the right arm fingers. The reliability of the sensor depends on the generated electric potential, the location of the device on the forearm, the strain applied by the fingers, and the flexibility of the S-CBNG device. The proposed work is non-invasive, robust, cost-effective and it does not require external power for wearable and smart devices.
      Graphical abstract image

      PubDate: 2017-02-11T01:32:20Z
  • Topological optimization of biomimetic sandwich structures with hybrid
           core and CFRP face sheets
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Zhi Sun, Dong Li, Weisheng Zhang, Shanshan Shi, Xu Guo
      Porous-core sandwich structures with CFRP face sheets have similar micro structures to biological tissues, for example, grass leaves. The sandwich structures are composed of two thin, stiff face sheets, which provide the primary in-plane structural stiffness, and a thick low-density porous core, which provides the functionalities and the majority of out-plane stiffness. However, the mechanical properties of these sandwich structures are often limited by local failures such as face-core debonding or core collapse. Inspired by the tree leaves with fractal distributed veins, which are larger and stiffer than grass leaves, in this paper, a topological optimization on the micro structures of core is conducted to achieve exceptional mechanical properties. By taking adhesive-area constraint, local-buckling constraint and embedding-volume constraint into consideration, a biomimetic hybrid core, which is similar to the fractal distribution of tree veins, is found to be an optimal core design for sandwich structures with CFRP face sheets.

      PubDate: 2017-02-11T01:32:20Z
  • Understanding the strain-dependent dielectric behavior of carbon black
           reinforced natural rubber – An interfacial or bulk phenomenon?
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Yanhui Huang, Linda S. Schadler
      Filler-polymer interactions are one of the keys to understanding the physical properties of polymer composites. These interactions give rise to an interface with specific properties that may have a nontrivial effect on the macroscopic properties of composites. Direct measurement of the interface properties at nanometer scale is usually unavailable. Thus, interface properties are often back calculated from the bulk response using a computational model. However, if the model does not take into account the morphology of the filler dispersion, the results can be misleading. Recently it has been found that the dielectric response of a carbon black filled natural rubber film can change dramatically upon stretching [M. Huang, Macromolecules 49, 2339 (2016)]. In this paper, we will show that this phenomenon can be largely explained by changes in filler cluster connectivity due to strain and is probably not caused by changes in the interfacial interactions. To support the argument, the polarization mechanism of the composites in the measured frequency range is analyzed and numerical models are developed to virtually reproduce the physical phenomenon as a function of strain. A power-law dependence of dielectric permittivity with strain is derived, which matches closely with the experimental results.

      PubDate: 2017-02-11T01:32:20Z
  • Interfacial properties and water resistance of epoxy and CNT-epoxy
           adhesives on GFRP composites
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Pyeong-Su Shin, Dong-Jun Kwon, Jong-Hyun Kim, Sang-Il Lee, K. Lawrence DeVries, Joung-Man Park
      Epoxy adhesives have been widely used to bond two different structural materials tightly together. Durability and strength of adhesion under aqueous and humidity circumstance have recently been deemed of particular importance for adhesives. This paper reports on studies of and the comparison of mechanical properties and interfacial durability in air as well as under moist conditions, or under water, of conventional bisphenol-A type epoxy and carbon nano tube (CNT) added epoxy adhesives. These studies included measurements of static contact angle, surface energy, and work of adhesion between CFRP laminate and CNT-epoxy adhesives to verify durability of the interfacial adhesion. Epoxy and CNT-epoxy adhesives were cured under aqueous condition and water penetration for comparatively evaluation. Cyclic lap shear tests were also used to evaluate the durability of lap shear strength of both epoxy and CNT-epoxy adhesives. The CNT-epoxy adhesive exhibited a significant retention in shear strength under moist conditions. During fracture the adhesives were evaluated using acoustic emission (AE) of the neat and CNT-epoxy adhesives in air and in aqueous conditions. Mechanical and interfacial properties of the CNT-epoxy adhesive were better than those of the neat epoxy adhesive, especially water resistance.

      PubDate: 2017-02-11T01:32:20Z
  • Influence of projectile nose shape and incidence angle on the ballistic
           perforation of laminated glass fiber composite plate
    • Abstract: Publication date: 12 April 2017
      Source:Composites Science and Technology, Volume 142
      Author(s): Md. Muslim Ansari, Anupam Chakrabarti
      In this study, experimental and finite element analyses of perforation behaviour of unidirectional glass fiber reinforced cross ply laminate have been presented, considering different projectile nose shapes, incidence velocities, incidence angle and laminate thickness. A pneumatic gun was used to propel 52 g steel projectile of diameter 19 mm at incidence velocity up to 300 m/s, where the projectiles are having different nose shapes such as ogival, conical, spherical and blunt. The target plate of size 140 mm × 140 mm and thickness 3.3 and 6.6 mm were made by unidirectional (UD) glass fiber with orientation (0°/90°/90°/0°) and (0°/90°/90°/0°)2 respectively. A three dimensional finite element model is developed using Lagrangian, eight nodded brick element in ANSYS/AUTODYN, v14.5. The elastic properties of GFRP laminate is obtained from tensile tests in Universal Testing Machine in the civil engineering laboratory of IIT Roorkee, India. The velocity and acceleration-time histories of projectile along with ballistic limit, energy absorption and damage pattern in target plate are presented. The results obtained from numerical simulation are having good correlation with the corresponding experimental values and many new interesting results are also generated especially for oblique impact.

      PubDate: 2017-02-11T01:32:20Z
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