A new analytical solution for cure-induced spring-in of L-shaped composite parts Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-12-07 Anxin Ding, Jihui Wang, Aiqing Ni, Shuxin Li
A new analytical solution for the prediction of cure-induced spring-in of L-shaped composite parts has been proposed based on modification of the model presented by authors (2017). In the newly proposed analytical solution, the flange length is incorporated into the formulation to theoretically derive the spring-in of corner of L-shaped composite part using shear-lag theory. Consequently, in addition to the cure process generated non-mechanical strain in the rubbery state in the through-thickness and length directions, the new solution can quantitatively give the correlation of spring-in of corner of L-shaped composite part with the flange length. Then, the newly proposed analytical solution is verified by the good agreement between the analytically calculated and experimentally measured spring-in angles for both the unidirectional and cross-ply L-shaped composite parts. Further numerical simulation on the elaborately selected L-shaped composite parts with various configurations also provides a favourable comparison with analytical results, showing the validity of newly proposed analytical solution.
A novel strategy for the synthesis of self-healing capsule and its application Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-12-08 Tao Sun, Xuejing Shen, Chong Peng, Hongyu Fan, Minjing Liu, Zhanjun Wu
Phenol formaldehyde (PF) resin capsules containing dicyclopentadiene (DCPD) as core materials are rationally designed and fabricated. The synthesis consists of preparation of polystyrene (PS) sphere, PF coating on PS sphere, followed by removal of PS core, amination modification and importing of DCPD. Solution phase switchable transport trough PF shell layer is key for the synthesis of DCDP@PF capsules. The resultant DCDP@PF capsules have a diameter of ∼500 nm, shell thickness of ∼50 nm, and core content of ∼45 wt%. The results show that DCDP@PF capsules have outstanding thermal stability with initial evaporation temperature (defined at 5% of weight loss), increased by ∼30 °C compared with that of pure DCPD, and good resistance to acetone. Preliminary results indicated that the prepared DCPD@PF capsules can effectivelly improve the mechanical properties of epoxy matrix as well as impart it self-healing properties. When 15 wt% DCPD@PF capsules were inttrouducd into epoxy matrix, 81.4% incresement in fracture toughness, 30.8% incresment in tensiles strength and 91.8% recovery in fracture toughness can be obtained. This work provides a new insight into the investigation of the fabraction of self-healing capsules.
Pull-out response of glass yarn from ettringite matrix: Effect of pre-impregnation and embedded length Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-12-06 O. Homoro, M. Michel, T.N. Baranger
The interest in textile-reinforced concrete materials has grown in recent years, owing to their many advantages (high strength, good corrosion resistance, non-toxicity, availability of raw materials, recyclability, etc.). However, the use of multifilament reinforcements for cements is challenging because the cement particles cannot fully penetrate the space between the inner filaments, thus leading to the decrease in the yarn–matrix bond and consequently the mechanical performance of the composite. To improve this bond, the glass yarns are typically pre-impregnated in a wet manner using mineral or organic powders. The objective of this work is to compare this conventional method with a recent method called pre-impregnation in a dry manner. It is based on using an alternating electrostatic field that allows powder to be impregnated into yarns. The pull-out response of alkali-resistant glass yarn embedded in the ettringite matrix is investigated and reported in this study. Three types of specimens were tested: a dry yarn, a yarn pre-impregnated in a wet manner with matrix particles, and a yarn pre-impregnated in a dry manner with different types of powder. Four embedded lengths are investigated and their effect on the result is discussed. We found that the pull-out behaviour is dependent on the pre-impregnation method, pre-impregnation powder type, and embedded length.
A multiscale elasto-plastic damage model for the nonlinear behavior of 3D braided composites Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-12-06 Chunwang He, Jingran Ge, Dexing Qi, Jiaying Gao, Yanfei Chen, Jun Liang, Daining Fang
A multiscale elasto-plastic damage model is developed to predict the nonlinear behavior of three-dimensional (3D) braided composites. In this model, the sequential multiscale method is applied to transfer the effective properties from microscale to mesoscale, and from mesoscale to macroscale. The constituents at the microscale consist of fiber, matrix and interface which are consistent with the mesoscale ones. The fiber is considered to be elastic and brittle, and the elastic damage model is applied to degrade the stiffness. For the epoxy matrix, a coupled elasto-plastic damage model is proposed to integrate the effects of plasticity and damage, and furthermore the paraboloidal yield criterion is adopted to characterize the different types of mechanical behavior in tension and compression. The bilinear constitutive relation based on the cohesive element is used to investigate the properties of interface. A user-defined material subroutine (UMAT) in the nonlinear finite element analysis software ABAQUS is written to implement the proposed model and determine the response for 3D braided composites under quasi-static tension. The numerical simulations are compared with the corresponding experiments and the results show that they agree well with each other.
Influence of process-induced shrinkage and annealing on the thermomechanical behavior of glass fiber-reinforced polypropylene Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-12-06 M. Mulle, H. Wafai, A. Yudhanto, G. Lubineau, R. Yaldiz, W. Schijve, N. Verghese
We investigate the influence of process-induced shrinkage and subsequent annealing on the thermomechanical behavior of unidirectional laminates made of continuous glass fiber-reinforced polypropylene (GFPP). We use two different industrial lamination processes: static hot-press (SHP), and double-belt press (DBP) that are characterized by different cooling rates and pressure levels and most importantly, by the use of a closed mold in the case of SHP manufacturing. We measure the longitudinal and transverse shrinkage during the manufacturing and annealing processes using embedded fiber Bragg gratings (FBGs). The SHP molding reveals much lower induced shrinkage in GFPP as compared to the DBP process, although the relatively slow cooling should promote a higher degree of crystallization. We ascribe this to the constraining effect of the metallic mold used with the SHP process. The poor thermal conductivity of the mold is also responsible for a layer-like crystal microstructure in the GFPP matrix, causing a specific relaxation effect during the post-process heating treatment. Annealing generates additional shrinkage that is due to an increased degree of crystallinity and to the partial relaxation of residual stresses. However, the thermal expansion properties remain impacted by the process-induced strain state of the GFPP laminates and are still process-dependent after annealing.
Highly flexible strain sensors based on polydimethylsiloxane/carbon nanotubes (CNTs) prepared by a swelling/permeating method and enhanced sensitivity by CNTs surface modification Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-12-05 Rong Zhang, Cheng Ying, Hao Gao, Qingting Liu, Xudong Fu, Shengfei Hu
Flexible sensors for large strain detection have recently been attracted the attention of researchers. This investigation reports a stretchable strain sensor in which carbon nanotubes (CNTs) were diffused into polydimethylsiloxane (PDMS) using a facile swelling/permeating method. The CNTs were further modified by using a silane coupling agent (SCA) to improve dispersion and the interaction between CNTs and PDMS. The CNTs permeated the skin layer of the PDMS composite and the inner core of PDMS contained few CNTs, forming a sandwich-like structure. The low CNTs content (0.48 wt%) and sandwich-like structure resulted in excellent composite flexibility which allowed work strains to exceed 350% and Young's modulus to increase from 0.25 MPa to 0.40 MPa. Surface modification of the CNTs improved their permeation depth and dispersion, which was shown to enhance composite sensitivity. The relative resistance change reached 4850% with a gauge factor of 20 by 1.0 wt% SCA modification. Cycled electromechanical properties showed a stable resistance response and sensitivity against strain. Therefore, the PDMS/CNTs nanocomposites prepared by swelling/permeating and CNTs surface modification in this study have various application potentials in the flexible sensor field.
High barrier properties against sulfur mustard of graphene oxide/butyl rubber composites Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-12-04 Long Zheng, Deyin Wang, Zongchao Xu, Liqun Zhang, Li Liu, Shipeng Wen
Protection against sulfur mustard (HD) is essential for the safety of the operators in the lab and in war. In this research, graphene oxide/butyl rubber (GO/IIR) composites were first prepared by a green method of latex compounding. This method achieved uniform dispersion of GO in IIR matrix for the GO content up to 2 phr (parts per hundreds of rubber). More importantly, there was a strong interfacial interaction between GO and IIR chains. When the GO content was 2 phr, the tear and tensile strengths of the GO/IIR composites were increased by 44% and 102%, respectively, compared with those of pure IIR. Additionally, it was found that the protective barrier properties against HD of GO/IIR composites increased with the increase in the GO content. When the GO content was 3 phr, a shielding filler network was formed by GO in the IIR matrix, and the diffusion coefficient of HD in IIR was decreased by 46%. The research results are of substantial importance for protection against HD and against more toxic gases or liquids.
Enhancing interfacial strength of epoxy resin composites via evolving hyperbranched amino-terminated POSS on carbon fiber surface Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-12-04 Lichun Ma, Yingying Zhu, Mengzhu Wang, Xiaobing Yang, Guojun Song, Yudong Huang
A self-synthesized octa(γ-chloropropyl) polyhedral oligomeric silsesquioxanes (POSS) and its evolutionary amino-terminated hyperbranched structure were introduced onto the carbon fibers (CFs) surface (CF-Gn-POSS-NH2, n = 1, 2 and 3) by chemically and successively grafting method to improve the interfacial properties of CFs/epoxy composite. The fiber surface structures could be tuned through regulating grafting generation (n) of CF-Gn-POSS-NH2, and the polarity and roughness of CF surface increased with the incremental dendritic generation number. Interfacial shear strength (IFSS), interlaminar shear strength (ILSS) and dynamic mechanical properties of the functionalized CFs composites improved as the grafting generation increased, which may be attributed to the varying degrees of chemical interaction, mechanical interlocking and resin wettability provided by hyperbranched Gn-POSS-NH2 interface. Moreover, the interfacial structure has been also speculated and analyzed.
The critical damage state controlling the tension-tension fatigue life of unidirectional fibre composites Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-12-04 Bent F. Sørensen
A fracture mechanics model is proposed for the prediction of the critical damage state corresponding to tension-tension fatigue failure of unidirectional fibre composites. The critical damage state is characterized by the development of longitudinal splitting cracks, enabling isolated damage zones with broken fibres to link up. The critical damage state can be expressed in terms of the size of damage zones with broken fibres. The critical damage zone size depends on the maximum applied cyclic stress level, the geometry of the splitting pattern and on the Mode II fracture energy of the composite. The model was used for predicting the critical damage size of a glass fibre composites subjected to cyclic loading. In a study reported in the literature, the damage zone size was determined experimentally by X-ray tomography just prior to fatigue failure. A good agreement was found between the predicted and reported damage zone sizes. Moreover, the reported failure involved longitudinal splitting in accordance with the model.
Orthotropic electro-thermal behaviour of highly-aligned carbon nanotube web based composites Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-12-04 Xudan Yao, Brian G. Falzon, Stephen C. Hawkins
A ‘forest’ of vertically aligned carbon nanotubes (CNTs), synthesised by chemical vapour deposition with an iron catalyst on a silicon substrate, is drawn into a horizontally-aligned CNT web. Previous work has shown that the electro-thermal properties of this web may be tuned by altering the individual length of the CNTs and the number of layers. This paper demonstrates, for the first time, that the orientation and multi-directional layering of the web provides further scope for tuning the electrical conductivity and heat distribution of the composite system. An analytical model based on the thermal conduction theory of anisotropic solids is proposed to predict the electrical conductivity of general multi-layered and multi-directional CNT webs.Specimens with different aspect ratios and web orientations were manufactured and their electrical conductivity and resistive heat distribution measured. All of them were shown to exhibit electrical properties and heating distributions which could be predicted or bounded by the analytical model. Consequently, through tuning the CNT web orientation and layup, various heating patterns may be obtained and designed for specific requirements.
DLC-treated aramid-fibre composites: Tailoring nanoscale-coating for macroscale performance Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-30 M. Kanerva, S. Korkiakoski, K. Lahtonen, J. Jokinen, E. Sarlin, S. Palola, A. Iyer, P. Laurikainen, L. Xuwen, M. Raappana, S. Tervakangas, M. Valden
This work aims to quantify the effect of a diamond-like carbon coating (DLC) treatment of aramid-fibres and to reveal the conversion of a fibre level performance leap on the macroscale mechanical behavior. The DLC based coating is applied directly on the reinforcement and laminates are infused with an epoxy matrix. After characterization of the coated surfaces, the performance of the composite is analyzed via interlaminar shear testing, fatigue testing and damage tolerance testing, microbond tests, and 3D finite element simulation using a cohesive zone model of the interface. The results show that the coating treatment improves the fatigue life and the S-N curve slope for the laminates while the residual strength after impact damage and environmental conditioning (water immersion at 60 °C) remains high. The scaling factor to convert the performance on macroscale was determined to be 0.17–0.39 for the DLC based fibre treatment.
Highly anisotropic functional conductors fabricated by multi-melt multi-injection molding (M3IM): A synergetic role of multiple melt flows and confined interface Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-30 Yanhao Huang, Zhengying Liu, Rui Chen, Shaodi Zheng, Changping Feng, Libo Chen, Wei Yang, Mingbo Yang
An anisotropic conductor with graphene nanoplatelets (GNPs) well planar aligned in PP matrix has been obtained in this work through multi-melt multi-injection molding (M3IM). In this method, a second composite melt penetrated the first melt and products with three layers (skin layer, intermediate layer and core layer) were obtained. The GNPs in the three layers was entirely planar oriented along machine direction (MD) owing to the second shear flow and confined interface between intermediate layer and core layer. The finely aligned structure drastically elevated in-plane thermal conductivity of intermediate layer to as high as 7.32 W m−1 K−1 and highlighted an average thermal conductive anisotropy of 20.86 under 25 wt. % GNPs loading, as well as provided a good electric conductivity of 0.03 S m−1 in MD while insulativity in perpendicular direction. Additionally, the M3IM composite performed well in mechanical properties with tensile strength (40.33 MPa) and Young's modulus (1.15 GPa). This M3IM manufacturing provides outstanding anisotropic properties to the injection products which possess a considerable potential application in unilateral conduction field.
The reinforcing effects of dendritic short carbon fibers for rigid polyurethane composites Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-29 Renliang Ma, Weiwei Li, Momo Huang, Ming Feng, Xiaojing Liu
The attainment of both strength and toughness was crucial for polymer composites. However, compared with the long fiber composites, conventional short fiber composites showed the low strength and toughness, due to the more stress concentrations generated around the fiber ends. In this work, a new morphological short carbon fiber reinforcement was fabricated by electrodeposition, which presented like the dendritic structure. The enhanced strength and toughness were realized by incorporating the dendritic short carbon fibers into rigid polyurethane (RPU) matrix. The tensile strength, impact strength and interfacial shear strength (ILSS) of the dendritic short carbon fibers/RPU composites were increased by 41.3%, 81.2% and 28.9%, respectively compared with pure RPU. The composites also exhibited the excellent dynamic mechanical properties. The satisfactory performance was mainly attributed to the pinning effect by the dendritic structure.
Fabrication of nanocomposite powders with a core-shell structure Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-29 Binling Chen, Bahareh Yazdani, Luiza Benedetti, Hong Chang, Yanqiu Zhu, Oana Ghita
This study presents a new process for producing nanocomposite powders for use in various manufacturing processes such as laser sintering or dry powder impregnation techniques for thermoplastic composites manufacture. Polyetherimide (PEI) was used as a polymeric coating/shell to encapsulate nanoparticles on the surface of poly ether ether ketone (PEEK) particles, which were used as a core matrix. Nanoparticles with different morphologies, known to enhance thermal and electrical performance of polymers: 2D graphene nanoplatelets (GNPs) and inorganic fullerene-like tungsten disulfide (IF-WS2) in different concentrations (0.1, 1, and 5 wt%) were incorporated in the shell structures. The coated powders had approximately the same particle size distribution as the uncoated, plain powders, which is an indication that the shell was in nm size and the coating process did not affect the overall size of the particles. Furthermore, the core-shell particles exhibit a smoother surface and an improved flowability after coating. The Transmission Electron Microscopy (TEM) images of the nanocomposite particles cross-section area confirmed the formation of core-shell structure, and the presence of the nanoparticles embedded into the shell layer. The scanning electron microscopy (SEM) images showed a homogeneous distribution of nanoparticles within the coating layer at lower nanoparticle concentrations (0.1 and 1 wt%).
Optimization of shear thickening fluid encapsulation technique and dynamic response of encapsulated capsules and polymeric composite Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-30 Xin Zhang, He Zhang, Pengfei Wang, Qian Chen, Xin Li, Youjin Zhou, Xinglong Gong, Zhong Zhang, En-Hua Yang, Jinglei Yang
In this work, shear thickening fluid (STF) was fabricated and encapsulated by using three different encapsulation methods for the first time. The mechanical properties of individual STF capsules were investigated to obtain optimal encapsulation method and formula. Much more energy can be absorbed for STF capsules during impact than that of quasi-static compression. The introduction of ultraviolet (UV) curable resin can significantly improve the static strength of STF capsule and thus enhance the handleability of STF capsule. The STF capsules synthesized through the two-step polymerization method show an elastic shell which can stand multiple impacts without any damage. This STF capsule possesses higher static strength and absorbs more strain energy than capsules synthesized through the other two methods. Furthermore, incorporation of the STF capsules into silicone gel enhances the energy absorption capacity of matrix material up to 71.3%.
Stacking sequence selection for defect-free forming of uni-directional ply laminates Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-30 K.J. Johnson, R. Butler, E.G. Loukaides, C. Scarth, A.T. Rhead
In order to meet demands for increased production rates of laminated composite components, aerospace manufacturing is being forced towards highly automated production processes such as forming. However, such automated processes increase the likelihood of inducing defects that lead to manufacturing cost and time inefficiencies which must be avoided. This paper introduces a new compatibility index, based on comparison of minimum energy (resin dominated) modes of adjacent plies that identifies stacking sequences which minimise defect formation. The index is validated using an experimental process where seven laminates with different stacking sequences are formed onto a complex tool geometry using an industrial double diaphragm former. Experimental results confirm that sequences with a high compatibility index produce defect-free parts at elevated temperature. Specifically, sequences with 90° interface angles (high compatibility indices) promote the most formable solutions and continuous 45° interfaces that spiral (e.g. 45/0/-45/90) which have a low compatibility index, produce the most problematic forming conditions owing to a shear locking behaviour. Laminate stacking sequence is thus shown to be a significant contributor, alongside temperature and vacuum rate, to quality of formed parts. The compatibility index method can therefore be used to increase production rate and quality in laminated composite manufacturing, leading to significant cost and efficiency savings.
A poly (vinyl butyral)/graphene oxide composite with NIR light-induced shape memory effect and solid-state plasticity Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-28 Yongkang Bai, Jiwen Zhang, Didi Wen, Peiwei Gong, Xin Chen
A NIR light-induced shape memory composite with light-induced plasticity was prepared by incorporating graphene oxide (GO) into cross-linked poly (vinyl butyral) (PVB). The cross-linked reaction between PVB and aromatic diisocyanate not only endowed the composites with excellent shape memory properties, but also offered the performance of solid-state plasticity due to the formation of carbamate bonds. The photo-responsive performance was introduced to the system by doping GO, a conventional photothermal reagent, resulting in excellent NIR light-induced shape memory properties and light-induced plasticity. According to the stress relaxation tests, the solid-state plasticity of composites could be regulated by the cross-linked density, GO, catalyst dosage and temperature. Moreover, the composites can be repeatedly programmed to a new permanent shape via a light-induced plasticity process, which still exhibited excellent light-induced shape memory properties even after 5 cycles of reconfiguration. The results demonstrate the promising prospect of these composites as actuator elements for applications in self-deployment devices and soft robotic.
Achieving vertically aligned SiC microwires networks in a uniform cold environment for polymer composites with high through-plane thermal conductivity enhancement Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-28 Ziming Shen, Jiachun Feng
Pre-constructing vertically aligned 3D thermally conductive fillers networks via unidirectional freeze casting method to prepare polymer composites with high through-plane thermal conductivity (TC) has recently attracted much attention. Here we proposed a strategy to fabricate anisotropic silicon carbide microwires (SiCMWs) networks in a uniform cold environment. The key point of our strategy was to design and make the anisotropic molds composed of materials with very different TC. We used a cuboid mold made of alumina sheets as top and bottom and PVC foam plate as side surfaces to fabricate vertically aligned SiCMWs networks in a cryogenic refrigerator. After impregnating of the networks into epoxy matrix, the obtained composites exhibited significant TC enhancement at an ultralow loading. The composite containing only 1.32 vol % of SiCMWs had a TC value of 0.62 W/(m K), which was 3.9 and 2.3 times that of pure epoxy and epoxy composite with random SiCMWs, respectively. Moreover, utilizing our method, the 3D networks with different orientation direction, dimensions or shapes could be also easily prepared only by designing and utilizing different molds.
Effect of glass fiber distributions on the mechanical and fracture behaviors of injection-molded glass fiber-filled polypropylene with 2-Hole Tension specimens Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-28 Jeong-Moo Lee, Jong-Sin Moon, Dongchul Shim, Byoung-Ho Choi
In this study, various fracture characteristics of plastic parts were experimentally investigated using newly designed specimens with 2 holes to observe the deformation and fracture behaviors of injection-molded plastic parts fabricated by short glass fiber (GF)-reinforced polypropylene (PP). This 2-hole tension (2HT) specimen affects the flow pattern of resin and the orientation of GF during the injection molding process, and various stress concentrations and distributions can be generated under a simple tensile load. The effects of rheological and mechanical variations of the resin on the deformation and fracture behavior of the test specimens were successfully investigated using the 2-hole tension specimens. In addition, it was confirmed that the non-uniform distribution of GF observed in the hole arrays region through the computed tomography (CT) scan is related to the crack propagation pathway, which ultimately affects the fracture behavior of the specimen.
Morphology and crystalline characteristics of polylactic acid [PLA]/ linear low density polyethylene [LLDPE]/ microcrystalline cellulose [MCC] fiber composite Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-27 Siddharth Mohan Bhasney, Purabi Bhagabati, Amit Kumar, Vimal Katiyar
The purpose of current work is to examine the influence of microcrystalline cellulose fibre on PLA/LLDPE polyblend and their characterization by the XRD, FESEM, TEM, DSC, POM and UTM. All three constituents were taken in different loading and then extruded in the twin screw extruder via melt extrusion technique. The tensile strength and percentage elongation of PLA/LLDPE/1% MCC was reduced to 56% and increased to 9% than pure PLA while UTS and % elongation were increased and decreased to ∼12 and ∼18% than PLA/LLDPE polyblend, respectively. The toughness of PLA/LLDPE/1% MCC was decreased to 1543 kJ/m3 from PLA 1942 kJ/m3. No change was observed in Tg of polyblend composite but the crystallization temperature was reduced by 5 °C. The spherulite growth rate of PLA/LLDPE/1 wt % MCC was 2.5 μm/min higher than neat PLA (1.1 μm/min) and PLA/LLDPE/3% MCC (1.8 μm/min). This study showed noticeable changes in various properties of the polyblend composites like mechanical, morphological, and crystallinity were influenced by the orientation of fibre, composition, polymer miscibility and interaction at the edges among the matrix, disperse phase and filler.
Percolation behavior of electromagnetic interference shielding in polymer/multi-walled carbon nanotube nanocomposites Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-24 Yu-Dong Shi, Jie Li, Yan-Jun Tan, Yi-Fu Chen, Ming Wang
Percolation behavior of electrical conduction that is related to the formation of conductive networks has been well demonstrated in conductive polymer composites (CPC). However, the electromagnetic interference (EMI) shielding of CPC is normally very low at the percolation threshold due to the different mechanism. Here, we first predicted the percolation behavior of EMI shielding existing in CPC because the EMI shielding effectiveness (SE) was mainly dependent on the conductivity of CPC if assuming the constantly magnetic permeability. In practice, we also found the percolation behavior of EMI shielding in the multi-walled carbon nanotube (MWCNT) filled poly(L-lactide) (PLLA) with good dispersion and isotactic polypropylene (iPP) with poor dispersion. Furthermore, the percolation threshold of EMI shielding was higher than the percolation threshold of electrical conduction. The percolation thresholds of EMI shielding and electrical conduction were ∼2.00 and ∼0.40 vol% for PLLA/MWCNT nanocomposites, and ∼5.40 and ∼1.40 vol% for iPP/MWCNT nanocomposites, respectively. The SEM and TEM image shows the sparse and dense MWCNT network near the percolation threshold of electrical conduction and EMI shielding, respectively, indicating that the sparse network of MWCNT can create high electrical conductivity as long as the formation of conductive paths. However, the high performance EMI shielding requires dense network of MWCNT.
Enhanced thermal conductivity of polyurethane composites via engineering small/large sizes interconnected boron nitride nanosheets Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-24 Zezhou Zhu, Chaowei Li, E. Songfeng, Liyan Xie, Renjie Geng, Cheng-Te Lin, Liqiang Li, Yagang Yao
With the decreased sizes of microelectronic devices, the excess heat has become one of the most important factors that shorten the lifetime of electronic components. As a result, developing materials with high-thermal conductivity is an urgent issue. In this study, we combine an ultrasonic exfoliation and evaporated self-assembly methods to prepare boron nitride nanosheets (BNNS)/thermoplastic polyurethane (TPU) composites with small (S) and large (L) sizes connected BNNS as additives. Our results indicate that BNNS/TPU nanocomposites have better thermal conductivity than TPU, and the optimum performance is achieved at 10 wt% BNNS(S/L-1/9)/TPU. This enhanced thermal conductivity is ascribed to the successful construction of effective thermal conductive pathway. The S-BNNS is connected to the adjacent L-BNNS in TPU, which can also form a dense structure. The formation of the continuous thermal conductive pathways and networks structure facilitate the heat diffusion throughout the composites, which are the key to achieving high thermal conductivity in polymer composites. Furthermore, these results may be helpful to the deeper understanding for the combined structure of fillers in polymer matrix, which will expand the scope of applications for these materials.
Fabrication of multi-walled carbon-nanotube-grafted polyvinyl-chloride composites with high solar-thermal-conversion performance Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-22 Xiaoning Shen, Minzun Ji, Shiming Zhang, Yujun Qin, Pu Zhang, Yapei Wang, Zhi-Xin Guo, Mingwang Pan, Zuoqi Zhang
The optical absorption properties of carbon nanotubes (CNTs) have attracted extensive research attention. Here we report the fabrication of sea-island structured polymer-based multi-walled CNT (MWNT) composite with high solar-thermal-conversion performance. MWNT-grafted 4-chloromethyl styrene (MWNTs-g-CMS) is prepared via esterification between carboxyl groups on the MWNT surface and the chloromethyl group of the CMS in the presence of a phase-transfer reagent in water. Covalent bonding between the CMS and the MWNTs is confirmed by Fourier transform infrared spectra. Thermogravimetric analysis of the MWNTs-g-CMS shows a mass percentage of the attached methyl styrene chains as high as 24.31 wt%. Subsequently, polymer-based MWNT-graft-polyvinyl-chloride (MWNTs-g-PVC) composite was prepared via an in-situ graft polymerization between the vinyl chloride and active styryl groups of the MWNTs-g-CMS. The MWNT grafting efficiencies in a series of MWNTs-g-PVC composites are 0.013–0.103%. The sea-island structure of the MWNTs-g-PVC composites and the fine dispersion of MWNTs in the island are verified by electron microscopy. The solar-thermal conversion performance of the MWNTs-g-PVC composites is studied. The composites exhibit excellent light-absorption properties that resemble a black body, and yield a higher solar-thermal conversion efficiency than the carboxylic MWNT (PVC/MWNTs-COOH) composites, which is attributed to the sea-island structure and the good dispersion of MWNTs in the islands.
Influence of conductive nano- and microfiller distribution on electrical conductivity and EMI shielding properties of polymer/carbon composites Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-23 Yevgen Mamunya, Lyudmila Matzui, Lyudmila Vovchenko, Oleksii Maruzhenko, Viktor Oliynyk, Sławomira Pusz, Bogumiła Kumanek, Urszula Szeluga
In this work, DC conductivity and EMI shielding characteristics in the frequency range of 25.5–37.5 GHz (Ka-band) of polymer composites based on ultrahigh-molecular-weight polyethylene (PE) and polypropylene (PP) containing different types of nano- and microfillers were studied. Graphene nanoplatelets (Gr), thermally exfoliated graphite (TEG), thermally treated anthracite (A) and dispersed metals such as iron (Fe) and copper (Cu) were used as conductive fillers. Two types of composites were formed: 1 – with ordered distribution of the filler particles in the form of conductive 3D network in polymer matrix (segregated structure), 2 – with random distribution of the filler particles. It was found that the percolation threshold for Gr and A filler is 100 and 10 times lower in the segregated system was 100 and 10 times lower than that for A filler with its random distribution in polymer matrix. Distinctly increased value of shielding efficiency (SET) in the segregated system can be explained by multiple internal reflection of electromagnetic wave in the network formed in the segregated structure. It was also found that the value of SE corresponds with the electrical conductivity of composites. However, for the same conductivity, higher values of SE were observed for the formed segregated structure in comparison with the literature data for composites with random filler distribution.
A numerical Bayesian-calibrated characterization method for multiscale prepreg preforming simulations with tension-shear coupling Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-19 Weizhao Zhang, Ramin Bostanabad, Biao Liang, Xuming Su, Danielle Zeng, Miguel A. Bessa, Yanchao Wang, Wei Chen, Jian Cao
Carbon fiber reinforced plastics (CFRPs) are attracting growing attention in industry because of their enhanced properties. Preforming of thermoset carbon fiber prepregs is one of the most common production techniques of CFRPs. To simulate preforming, several computational methods have been developed. Most of these methods, however, obtain the material properties directly from experiments such as uniaxial tension and bias-extension where the coupling effect between tension and shear is not considered. Neglecting this coupling effect deteriorates the prediction accuracy of simulations. To address this issue, we develop a Bayesian model calibration and material characterization approach in a multiscale finite element preforming simulation framework that utilizes mesoscopic representative volume element (RVE) to account for the tension-shear coupling. A new geometric modeling technique is first proposed to generate the RVE corresponding to the close-packed uncured prepreg. This RVE model is then calibrated with a modular Bayesian approach to estimate the yarn properties, test its potential biases against the experiments, and fit a stress emulator. The predictive capability of this multiscale approach is further demonstrated by employing the stress emulator in the macroscale preforming simulation which shows that this approach can provide accurate predictions.
Electrical properties of multifunctional Z-pinned sandwich composites Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-20 K. Grigoriou, R.B. Ladani, A.P. Mouritz
The use of z-pins to controllably increase the electrical conductivity and to detect damage in sandwich composites is investigated. Sandwich materials with polymer foam core or balsa wood core were reinforced in the through-thickness direction with z-pins made of metal (copper, titanium) or carbon fibre composite. The through-thickness electrical conductivity of the sandwich composites was increased by up to nearly seven orders of magnitude by z-pins, although the in-plane conductivity was not affected significantly. The increase to the through-thickness conductivity was controlled by the electrical properties, volume content and/or insertion angle of the z-pins. Due to the increased conductivity, z-pins were used for in-situ and real-time electrical-based monitoring of damage caused by crushing or skin-core interfacial debonding of sandwich composites. In addition, the z-pins increased the flatwise compressive strength and in-plane fracture resistance of the sandwich composites. It is demonstrated that z-pins can increase multiple properties concurrently, including the electrical and mechanical properties, and also provide the functionality for in-situ real time damage detection.
Noncovalent functionalization of carbon nanotubes via co-deposition of tannic acid and polyetheylenimine for reinforcement and conductivity improvement in epoxy composite Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-20 Yaxin Chen, Wei Wei, Ye Zhu, Jing Luo, Xiaoya Liu
In this paper, a novel strategy via one-pot co-deposition of tannic acid (TA) and polyethyleneimine (PEI) to modify the MWCNTs was reported, which allows to modify MWCNTs with polymer via robust linkage in a convenient, green and nondestructive way. The obtained TA-PEI modified MWCNTs (TA-PEI/MWCNTs) with abundant amine and imine groups have good dispersibility in various solvents as well as epoxy resin. Epoxy composites reinforced with TA-PEI/MWCNTs were prepared and their mechanical properties was studied in detail. The modification of MWCNTs by TA-PEI could not only enhance the compatibility of MWCNTs with epoxy resin, but also improve the interface interaction between MWCNTs and epoxy matrix caused by the curing reaction between epoxy and amine groups on MWCNTs surface. With the 0.4 wt% loading of TA-PEI/MWCNTs, the impact strength and tensile strength of the composite reach 40.51 kJ/m2 and 80.83 MPa, improved by 154% and 148% compared with pristine MWCNTs/epoxy composites, respectively, clearly demonstrating the important role of TA-PEI modification. In addition, the glass transition temperature (Tg) of the composite is 152.4 °C which is significantly higher than pure epoxy resin (136.9 °C) and MWCNTs/epoxy (142.0 °C). Furthermore, the electrical conductivity of the epoxy composite was also remarkably enhanced.
Carbon nanotubes-bridged-fumed silica as an effective binary nanofillers for reinforcement of silicone elastomers Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-17 Junhua Kong, Jiaotong Sun, Yuejin Tong, Qingqing Dou, Yuefan Wei, Warintorn Thitsartarn, Chee Chuan Yeo Jayven, Chaobin He
The incorporation of nanofillers into polymeric matrix has been proven to be an effective route to reinforce their mechanical properties, and the usage of binary fillers that combines the advantages of the two fillers could lead to further property enhancement. In this work, binary nanofillers consist of multi-walled carbon nanotubes (MWCNTs)-bridged fumed silica (FSiO2) were synthesized for the first time by Pt coupling reaction of methyldiethoxysilane (MDES) modified MWCNTs and triethoxyvinylsilane (TEVS) functionized SiO2, in which MDES modified MWCNTs was synthesized by reacting OH-functionized MWCNTs with MDES, while TEVS-FSiO2 was obtained by reacting fume silica with TEVS. The binary MWCNTs-bridged-FSiO2 was introduced into liquid silicone rubber (LSR) for mechanical reinforcement. It is shown that the interfacial interaction between binary fillers and LSR matrix is significantly enhanced due to the chemical bridging as well as the excess TEVS molecules on SiO2, and the Young's modulus, tensile strength and tear strength of the LSR could be increased by 64%, 29% and 52%, respectively, with incorporation of only 0.25 phr of MWCNTs for the binary fillers. The observed mechanical enhancement could be attributed to good interfacial interaction between the fillers and LSR due to the existence of SiO2 (with excess matrix compatible molecules) on the surface of MWCNTs, which facilitate the filler dispersion in LSR matrix and the promote stress transfer from matrix to MWCNTs, as well as the advantages of extremely high aspect ratio and excellent mechanical strength of MWCNTs.
The thermal degradation and dynamic mechanical properties modeling of MWCNT/glass fiber multiscale filler reinforced polypropylene composites Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-17 N. Rasana, K. Jayanarayanan, B.D.S. Deeraj, K. Joseph
The present work is focused to explore the influence of multiscale fillers (nano scale multiwalled carbon nanotubes (MWCNTs) and micro scale Glass fibers) on the thermal degradation and dynamic mechanical properties of polypropylene (P). MWCNTs weight fraction was varied up to 5 wt% for a fixed glass fiber fraction of 20 wt% and the resultant composite was characterized using X-ray diffraction, Scanning and Transmission Electron Microscopy. Hybrid composites with 2 wt% MWCNTs presented 101% increase in the activation energy for thermal degradation compared to the base matrix. The synergism of multiscale fillers could be clearly verified by the improved storage and loss modulus of the composite with 3 wt% MWCNT which is related to better interfacial interaction of fillers with the matrix. The lowering of tan δ peak suggested the rise in entanglement density of polymer chains on the fillers and decrease in the damping behavior of the composites was observed till 3wt% of MWCNTs both by experimental and theoretical model values. Beyond 3 wt% of MWCNTs agglomeration effects caused decline in the dynamic mechanical properties.
Effect of graphene oxide-carbon nanotube hybrid filler on the mechanical property and thermal response speed of shape memory epoxy composites Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-17 Enliang Wang, Yubing Dong, MD Zahidul Islam, Laiming Yu, Fuyao Liu, Shuaijie Chen, Xiaoming Qi, Yaofeng Zhu, Yaqin Fu, Zhaohe Xu, Ning Hu
Shape memory polymers (SMPs) will come to act an indispensable part in numerous aspects of human activity. However, the low mechanical strengths and thermal conductivities of SMPs have largely restricted their applications. Remarkable improvements in the mechanical properties and thermal conductivities of SMPs via introducing thermal conductivity fillers have been achieved, though the fillers acted as obstructors or promoters for the thermal response speed of SMPs were unclear. In the present study, ternary hybrid polymeric shape memory composites of graphene oxide/carbon nanotube/waterborne epoxy (GO/CNT/WEP) were fabricated, where GO acted as a non-covalent dispersant for CNT in WEP and as a reactive secondary reinforcing agent to improve the mechanical strength and thermal conductivity of WEP. The experimental results showed that GO and CNT were uniformly dispersed and well incorporated into WEP matrix, significantly enhanced the mechanical properties, thermal conductivity and thermal response speed of the GO/CNT/WEP composites. Moreover, the thermal response speed of the shape memory composites was controlled by their thermal conductivity at low filler content, while the storage modulus was the dominant factor for the thermal response speeds of the shape memory composites at filler content higher than 2 wt%.
Quantitatively identify and understand the interphase of SiO2/rubber nanocomposites by using nanomechanical mapping technique of AFM Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-16 Chenchen Tian, Guangyu Chu, Yuxing Feng, Yonglai Lu, Chunmeng Miao, Nanying Ning, Liqun Zhang, Ming Tian
The interphase between nanofillers and rubber matrix, also known as “bound rubber (BR)” composed of a tightly BR (TBR) layer that strongly interacts with the filler and a loosely BR (LBR) layer that is physically adsorbed, plays an important role in the properties of rubber nanocomposites. Up to now, there is seldom direct evidence of such interfacial double layer structure and their thickness. In this study, we quantitatively identified the interphase of a representative nano silicon dioxide (SiO2)/rubber composites by using peak force quantitative nanomechanical mapping (PFQNM) mode of Atomic Force Microscope (AFM). The thickness of interphase was quantitatively obtained, and the double layer structure of interphase was directly identified based on PFQNM images and the corresponding force-distance curves, and was further evidenced by high resolution transmission electron microscopy. We further studied the effect of molecular polarity on interphase of SiO2/hydrogenated nitrile butadiene rubber (HNBR) composites. Interestingly, the molecular polarity of HNBR has almost no effect on the thickness of TBR layer but has a significant effect on the LBR layer, leading to the remarkable increase in the total interfacial thickness of the composites with increasing the acrylonitrile content. The mechanism for the formation of interfacial double layer structure of BR and the effect of molecular polarity on the double layer structure was discussed. This study provides a simple method to identify and deeply understand the double layer structure of the interphase, and thus provides guidance for the design of interphase for the preparation of high performance rubber nanocomposites.
Damage mechanisms in elastomeric foam composites: Multiscale X-ray computed tomography and finite element analyses Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-16 Brendan P. Croom, Helena Jin, Bernice Mills, Jay Carroll, Kevin Long, Judith Brown, Xiaodong Li
To understand the mechanisms of damage initiation and propagation in glass microballoon (GMB)/silicone elastomer matrix syntactic foam composites, multiscale X-ray computed tomography images obtained during in situ compression were analyzed using quantitative image processing and digital volume correlation (DVC) techniques. High-resolution tomograms revealed that both the initiation and propagation of GMB collapse depended on the local clustering of GMBs, leading to the formation of pseudo-crush bands in the composite. This resulted in prominent bands of axial strain variation that grew to several millimeters in length as revealed by DVC. A new mechanism based on stress redistribution around collapsed GMBs is proposed to explain the damage propagation, which is supported by finite element analysis and successfully captures the effects of cluster orientation on the observed damage.
Low velocity impact response of fabric reinforced hybrid composites with stratified filled epoxy matrix Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-15 M. Bunea, A. Cîrciumaru, M. Buciumeanu, I.G. Bîrsan, F.S. Silva
The aim of this study was to investigate the influence of the matrix properties, number of the carbon and aramid layers and fiber orientation on low velocity impact behavior of the fabric reinforced hybrid composites with stratified filled epoxy matrix. The impact tests were performed with the drop weight impact system at 90.629 J of energy level. The damage areas were analyzed by the visual inspection and tomographic images. The results showed that the matrix properties have a great influence over the fracture mode of the hybrid composites, while the fault degree of the damaged areas depends on the fiber orientation. The highest impact resistance was obtained in the case of hybrid composites with 0° ply orientation.
Temperature-responsive and piezoresistive performances of poly(N- isopropylacrylamide)-grafted reduced graphene oxide smart fiber Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-14 Hui Ma, Huanxia Zhang, Jianda Cao, Mingqiong Tong, Jianwei Zhao, Yifei Li, Hong Xu, Wen Wu
In this work, temperature-responsive poly(N-isopropylacrylamide) (PNIPAm) was covalently grafted onto the edge of graphene oxide (GO) sheets through a facial method cross-linked by 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) and N-hydroxysuccinimide in aqueous solution at room temperature. Then, the dispersion was wet spun to form a GO composite fiber. Scanning electron microscopy images suggest that severe edge distortions occur in PNIPAm-g-rGO hybrid fibers, indicating the covalent attaching of PNIPAm molecules onto the edge of graphene sheets. The PNIPAm-g-rGO fibers showed more favorable and improved electrical property than the pristine rGO fibers. Moreover, the coil-to-globule transition of the end-grafted PNIPAm chains was partially restricted by graphene sheets in the composite fiber, thereby causing the elevation of the phase transition temperature. Switching test of temperature-responsive versus electrical conductivity function has proved that the observed temperature-induced electrical conversion of the fibers was highly reversible and reproducible. Simultaneously, the composite fiber exhibited higher piezoresistive sensitivity compared with neat fiber. This smart fiber has shown remarkable potential for intelligent strain sensors, textiles, actuators, wires and on/off switches.
Selective location and migration of poly(methyl methacrylate)- grafted clay nanosheets with low grafting density in poly(methyl methacrylate)/poly(styrene-co-acrylonitrile) blends Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-13 Ting Liu, Haimo Zhang, Min Zuo, Wenjing Zhang, Weipu Zhu, Qiang Zheng
The location and migration of poly (methyl methacrylate)-grafted clay (clay-g-PMMA) nanosheets with low grafting density in a phase-separated polymer blend of poly (methyl methacrylate)/poly (styrene-co-acrylonitrile) (PMMA/SAN) was investigated. The grafting density and molecular weight for grafted PMMA chains on the surface of clay nanosheets was about 0.04 chains/nm2 and 7.8 × 104, respectively, indicating that the grafted chains might exhibit the mushroom-like distribution. With phase separation of PMMA/SAN blend matrix, the well-dispersed clay-g-PMMA nanosheets in the blend matrix were first located in the SAN-rich phase and then gradually migrated to the interface between PMMA and SAN. The first abnormal location of modified clay in the blend matrix might be attributed to the favorable interaction between clay-g-PMMA and SAN induced by the miscibility of grafted PMMA/surrounding SAN chains and the unfavorable interaction between clay-g-PMMA and PMMA without any interpenetration of grafted and matrix chains. The enhanced miscibility between grafted PMMA and surrounding SAN just began to be destroyed after being annealed for a long time, resulting in the final migration of clay-g-PMMA to the interface of PMMA/SAN (thermodynamic equilibrium state).
Concurrently improved dispersion and interfacial interaction in rubber/nanosilica composites via efficient hydrosilane functionalization Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-13 Chengfeng Zhang, Zhenghai Tang, Baochun Guo, Liqun Zhang
Surface modification of fillers has a profound influence on the dispersion of filler and interfacial adhesion, and thus the final performance of polymer-based composites. In this contribution, the modification of silica by polymethylhydrosiloxane (PMHS) is conducted via an efficient and fast tris(pentafluorophenyl)borane-catalyzed functionalization, which can be completed within a few minutes at room temperature. A highly hydrophobic surface and an uncompromised reactivity are concurrently observed in the modified silica. By comparison between the composites filled with pristine and modified silica, it is revealed that such PMHS modification can not only improve the dispersibility of silica by lowering the surface energy, but also enhance the interfacial interaction in virtue of the reactivity of the residual Si-H bonds. With a PMHS grafting content as low as 1.5 wt%, the modified composite exhibits tremendous improvements in mechanical properties (116% increase in modulus) and dynamic performances (116% increase in wet traction and 26% reduction in rolling resistance). Considering the superior overall performance of the modified composites, together with the simplicity and rapidity of the modification process, we envision that the hydrosilane-modified silica has great potential in the fabrication of high-performance polymer composites such as energy-saving tire treads.
Facile synthesis of magnetic rubber foam with cellular structure by one-step solution foam processing for application in giant magnetostriction Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-13 Yan Wang, Guizheng Guo, Yaya Zhou, Youyi Sun, Diansen Li, Yaqing Liu, Guizhe Zhao
Generally, magnetostriction elastomer were based on magnetic field-induced strains of elastomer matrix, resulting from the rotation of magnetic particle in elastomer matrix. However, such magnetostriction was relatively small and large hysteresis. Here, a new class magnetic rubber foam with cellular structure was developed and synthesized by the one-step solution foam processing. The magnetic rubber foam did not only show larger magnetostriction value of ca.11.0% comparing to previous magnetostriction elastomer, but also was few remanent magnetostriction and rapid response (ca. 1.0s). Furthermore, a new mechanism of magnetostriction was proposed for explaining the high performance magnetostriction. These provide a universal route for the rational design of magnetostriction materials with high performance for various applications.
Polarization-induced alignment of azobenzene/fluorinated polyimide for three-dimensional shape-persistent and photo-responsive elastic helixes Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-13 Shuangwen Li, Yiyu Feng, Weizhe Wang, Tengxiao Ji, Junkai Han, Peng Long, Chen Cao, Wei Feng
Three-dimensional (3D) macroscopic chiral helixes using anisotropic polymer assembly shows a great potential for designing micromechanical systems and soft robotics. However, movement of flexible polymer chains make the fabrication of 3D macroscopic helical ribbons with excellent shape stability under high temperature or multitudes of stretch/strain cycling very problematic. This paper presents the polarization-induced alignment of a non-LC supramolecular azobenzene-polyimide assembly (Azo/f-PI). We prepare 3D left- or right-handed Azo/f-PI helixes with shape-persistence, high-elasticity and photoresponisivity by large-area molecularly oriented assembly films. The Azo/f-PI helix treated at 100 °C for 10 min retains its linear-elastic deformation with 77.16% retention of the elastic potential energy density (0.304 J/g), and an extremely low permanent deformation of 3.68% upon 1000 stretching-relaxation cycles. Moreover, the 3D helix exhibited a light-driven elongation up to about 175.0% of the original length under UV irradiation. This 3D high-elastic helix with excellent shape persistence and photo-responsive actuability opens a gate for micromechanical control.
Preparation and properties of cyanate-based wave-transparent laminated composites reinforced by dopamine/POSS functionalized Kevlar cloth Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-12 Lin Tang, Jing Dang, Mukun He, Junyou Li, Jie Kong, Yusheng Tang, Junwei Gu
Combining method of dopamine/polyhedral oligomericsilsesquioxane (DA/POSS) was firstly performed to functionalize the surface of Kevlar (POSS-g-Kevlar@PDA, f-Kevlar) cloth. And then the corresponding f-Kevlar cloth/bisphenol A cyanate ester (BADCy) matrix wave-transparent laminated composites were successfully fabricated by the method of impregnation, lamination followed by mould pressing. The obtained wave transmission efficiency (T) of 92.0% for f-Kevlar cloth/BADCy wave-transparent laminated composites was higher than that of pristine Kevlar cloth/BADCy wave-transparent laminated composites (T of 88.4%). Flexural strength and interlaminar shear strength (ILSS) of the f-Kevlar cloth/BADCy wave-transparent laminated composites were also significantly increased to 236.3 MPa and 28.5 MPa, increased by 28.8% and 73.7%, in comparison to that of pristine Kevlar cloth/BADCy wave-transparent laminated composites (flexural strength of 183.5 MPa and ILSS of 16.4 MPa), respectively. And the corresponding glass transition temperature (Tg) and heat resistant index (THRI) of the f-Kevlar cloth/BADCy wave-transparent laminated composites was 226.3 °C and 232.8 °C, respectively.
Novel 3D network porous graphene nanoplatelets /Fe3O4/epoxy nanocomposites with enhanced electromagnetic interference shielding efficiency Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-12 Haijun Liu, Caizhen Liang, Jianjun Chen, Yuewen Huang, Fei Cheng, Fubin Wen, Bingbing Xu, Bin Wang
In this work, a novel and facile technique, epoxy-water-inorganic filler suspended emulsion polymerization, was proposed to fabricate 3D network porous graphene nanoplatelet (GNP)/Fe3O4/epoxy nanocomposites with low density of 0.34–0.73 g/cm3. The obtained porous nanocomposite with 7 wt% graphene nanoplatelets and 7 wt% Fe3O4 nanoparticles loading exhibited satisfactory specific electromagnetic interference (EMI) shieling effectiveness of ∼37.03 dB/(g/cm3), which was much higher than that of the solid counterparts (28.30 dB/(g/cm3)). In addition, the porous GNP/Fe3O4/epoxy nanocomposites also possessed outstanding thermal stability and mechanical property, which makes it a potential EMI shielding material in the fields of aerospace and electronic industries.
Nanoindentation mapping of multiscale composites of graphene-reinforced polypropylene and carbon fibres Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-12 Patricia Enrique-Jimenez, Susana Quiles-Díaz, Horacio J. Salavagione, Juan Pedro Fernández-Blázquez, M.A. Monclús, Roberto Guzman de Villoria, Marián A. Gómez-Fatou, Fernando Ania, Araceli Flores
The local mechanical properties of hierarchically reinforced laminates of graphene-isotactic polypropylene (iPP) and carbon fibres are investigated by nanoindentation. Carbon fibre fabrics are alternated with films of iPP reinforced with different graphene contents and types (pristine and modified with iPP brushes). The distribution of the mechanical data obtained around one isolated carbon fibre at the boundary with the polymer layer is compared with a similar analysis far away from any fibre. In the case of neat iPP, a high E′ tail can be identified with a micrometre-sized interphase showing distinct properties from those of the polymer matrix. With increasing amount of graphene, the E′ distribution including the high E′ tail progressively shifts to higher values. It is suggested that graphene platelets accumulate at the front of the ply due to the filtering effect of the carbon fibres giving rise to a transition region, superimposed on the interphase, with enhanced properties. Nanoindentation studies reveal that the chemical modification of graphene by short-chain iPP lowers the reinforcement of the nanofiller, both near and far away from the fibres front. On the other hand, indentation push-in tests suggest that modified graphene increases the resistance of the laminate under shear stress conditions. However, from the point of view of overall performance, it lowers the electrical conductivity across the laminate. The work offers a discussion of the role of graphene type and content on the properties of the multiscale composite.
Enhanced fracture toughness of hierarchical carbon nanotube reinforced carbon fibre epoxy composites with engineered matrix microstructure Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-12 M. Shukur Zainol Abidin, Tomi Herceg, Emile S. Greenhalgh, Milo Shaffer, Alexander Bismarck
Fibre reinforced hierarchical composites further reinforced with up to 25 wt.% of carbon nanotubes (CNTs) were manufactured using a wet powder impregnation route. Microstructural heterogeneity in the matrix of these laminates was engineered during wet powder impregnation to produce CNTs rich regions with spatial separation. The Mode I fracture toughness of these heterogeneous hierarchical composites increased by 41% and 26% compared to that of baseline carbon fibre epoxy composites and hierarchical composites with homogeneously distributed CNTs throughout the matrix with similar CNT content, respectively. Increased crack path tortuosity was observed to contribute to this increase in fracture toughness. The interlaminar shear strength was unaffected by the matrix microstructural heterogeneity.
Ultrathin and anisotropic polyvinyl butyral/Ni-graphite/short-cut carbon fibre film with high electromagnetic shielding performance Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-12 BianYing Wen, XueJiao Wang, Yang Zhang
Ultrathin, flexible and anisotropic polyvinyl butyral (PVB)/graphite coated with nickel (Ni-Gr)/short-cut carbon fibre (SCF) cast films were fabricated using a convenient solution casting method. The effects of the filler components, contents, and their distribution structures on the electromagnetic shielding effectiveness (SE) of the composites are investigated. The results indicate that the hybridisation and distribution of fillers with different shapes could significantly improve the electromagnetic shielding performance. The anisotropic SE of the composites is due to the orientation of the SCFs in the casting direction, which was induced by the traction from the carrier tape of the casting machine. Moreover, the measured electromagnetic SE in the perpendicular direction was higher than that in the casting direction. The experimental results showed that the prepared composite films had excellent anisotropic SE in the measured frequency range of X band. The SE and specific SE of the PVB/Ni-Gr/SCF cast film with a mass ratio of 69/26/5 are 32 dB and 159 dB/mm, and 20 dB and 101 dB/mm, across and along the casting direction, respectively. The SE difference between the two directions of the microwave shielding material provides the potential to prepare a direction selective composite with an ultrahigh electromagnetic shielding performance. Moreover, the prepared composites showed great potential as microwave shielding materials in military and civilian applications.
Fabrication and investigation on the Fe3O4/thermally annealed graphene aerogel/epoxy electromagnetic interference shielding nanocomposites Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-09 Yiming Huangfu, Chaobo Liang, Yixuan Han, Hua Qiu, Ping Song, Lei Wang, Jie Kong, Junwei Gu
Ethylenediamine functionalized Fe3O4 (NH2-Fe3O4) nanoparticles and graphene oxide (GO) were compounded firstly, followed by the addition of L-ascorbic acid, to obtain the Fe3O4/thermally annealed graphene aerogel (Fe3O4/TAGA) by thermal annealing method. And the Fe3O4/TAGA/epoxy nanocomposites were then fabricated via template-casting method. When the mass ratio of GO to NH2-Fe3O4 was 2:1 and the total mass fraction of Fe3O4/TAGA was 2.7 wt% (1.5/1.2 wt% Fe3O4/TAGA), the obtained Fe3O4/TAGA/epoxy nanocomposites presented the highest electromagnetic interference shielding effectiveness (EMI SE of 35 dB in the X-band), much higher than that of epoxy nanocomposites (10 dB) filled with the same Fe3O4/thermal annealing graphene oxide (Fe3O4/TAGO) loading. Meantime, the corresponding Fe3O4/TAGA/epoxy nanocomposites also presented the outstanding electrical conductivity of 27.5 S/m.
Eliminating lightning strike damage to carbon fiber composite structures in Zone 2 of aircraft by Ni-coated carbon fiber nonwoven veils Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-09 Yunli Guo, Yongzheng Xu, Qinglin Wang, Qi Dong, Xiaosu Yi, Yuxi Jia
By using standardized Waveforms C and D, this study explored the lightning strike protection (LSP) effectiveness of nickel coated carbon fiber nonwoven veils (Ni-CFNVs) on protecting the carbon fiber composite structures in Zone 2 (aircraft lightning zoning). The post-lightning damage was evaluated by visual inspection, ultrasonic scan and residual strength test. Results showed that the Ni-CFNV of 70 g/m2 eliminated lightning strike damage inflicted by both waveforms and it even performed better than the commercial expanded copper foil of 73 g/m2. Therefore, the Ni-CFNV will be a promising alternative to metal mesh for eliminating lightning strike damage to the structures in Zone 2. The remarkable LSP effectiveness of Ni-CFNV can be explained by its integration of high electrical conductivity of Ni-coating and prominent ablation resistance of carbon fiber. The experiments indicate that not only the electrical conductivity, but also the ablation resistance of LSP layer greatly influences the LSP effectiveness.
Self-suspended starch fluids for simultaneously optimized toughness, electrical conductivity, and thermal conductivity of polylactic acid composite Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-09 Qiao Yu, Yun Li, Lu Han, Xianze Yin, Jing Xu, Yinshan Zhou, Dongzhi Chen, Zhengliang Du, Luoxin Wang, Yeqiang Tan
It is challenging to fabricate a starch derivative with a plasticizing effect and good dispersion in a poly(lactic acid) matrix to achieve desirable performance. In this study, self-suspended starch fluids composed of modified granules as the core and polyethylene glycol-substituted tertiary amines as the shell were first fabricated via a combined carboxymethylation and acylation reaction. The as-prepared starch fluids exhibited liquid-like behavior and had semiconductor electric conductivity (4.91 × 10−5 S/cm) at room temperature without a solvent. The modulus of starch fluids was clearly reduced under the heating process and exhibited its initial flow properties upon cooling, displaying thermo-reversible behavior. The resultant fluids were then incorporated into a poly(lactic acid) matrix to produce fully biodegradable composites with desirable performance. At a loading level of 10 wt%, starch fluids exhibited simultaneous enhancements in elongation at break (increase of 164.7%) and thermal conductivity (increase of 119%) of PLA composites compared to pure PLA, attributable to the good dispersion and heat-transfer properties of starch fluids. In addition, PLA composites with 10 wt% loading of starch fluids demonstrated excellent antistatic performance (3.08 × 10−4 S/cm), suggesting that polar groups of the PLA structure and PEG groups of starch fluids contributed synergistically to the electrical conductivities of composites. These results indicate that starch fluids are promising antistatic agents and plasticizers for potential applications in biodegradable materials.
Achieving high dielectric permittivity, high breakdown strength and high efficiency by cross-linking of poly(vinylidene fluoride)/BaTiO3 nanocomposites Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-09 Ze-Hui Dai, Ting Li, Yang Gao, Jun Xu, Jinliang He, Yunxuan Weng, Bao-Hua Guo
Polymer nanocomposite dielectrics have drawn increasing attention recent years. However, dispersion of high-ε nanoparticles causes decreased breakdown strength and increased loss tangent. High dielectric permittivity, high breakdown strength, low dielectric loss and high charging-discharging energy efficiency are hard to achieve at the same time. In this research, in order to achieve all these goals, a combination method consists of cross-linking and dispersion of high-ε nanoparticles was carried out. The cross-linking points limit polymer chain mobility in the amorphous phase, providing lower dielectric loss and lower conductivity. Therefore, breakdown strength increased from 402.8 MV/m of PVDF to 517.2 MV/m of cross-linked PVDF. By dispersing coated BaTiO3 nanoparticles, followed by cross-linking, cross-linked nanocomposites with higher ε, higher breakdown strength and higher efficiency compared with the polymer matrix were prepared. The maximum discharging energy density reached up to 14.1 J/cm3, about 70% higher than 8.02 J/cm3 for pristine PVDF. This research provides us a novel approach to achieve all these goals by a combination of cross-linking and dispersion of coated BT nanoparticles.
Indirect morphological analysis of particles in polymer particle composites via non-destructive permittivity measurements Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-09 Mike Mühlstädt, Matthias M.L. Arras, Philip Zimmer, Klaus D. Jandt, Jörg Bossert
Polymers with special properties (e.g. electrical, optical or mechanical) are often obtained via the addition of fillers. The composites' final properties rely on the preservation of these fillers during blending, which is, in particular, challenging for high aspect ratio particles, like shear-sensitive flaky particles (ssFP). Thus, in cases of ssFP off- or in-line monitoring is indicated. This study addresses the lack of suitable non-destructive monitoring methods appropriate for ssFP possessing a thickness below 1 μ m and an area equivalent diameter of several 10 μ m . An elegant method was developed to validate the integrity of ssFP within composites, which is based on the measurement of the composites' permittivity and applying precise micro-structure property correlations to indirectly determine the fillers' morphological features. The main hypothesis tested was that a reduction of the particles aspect ratio by a factor of larger than 5 can be detected by the measurement of the composites' permittivity. In this study, polyethylene or epoxy resin were blended with the mica-based ssFP Iriodin 153 which features a mean area equivalent diameter of 42 μ m and an average thickness of about 1 μ m . The micro-structure property correlation presented by G. Ondracek [Z. f. Werkstofftechnik, 8:280-287, 1977] provided the necessary theoretical backbone to indirectly infer geometrical changes to the ssFP from permittivity measurements. An excellent match was obtained between the indirectly (permittivity measurements) and the directly (ashing of matrix and subsequent scanning electron microscopy) determined particles' aspect ratios which related directly to the particles' area equivalent diameter because the thickness of the particles was almost constant. This preliminary study established the presented technique as a promising non-destructive test method to monitor the integrity of ssFPs embedded in a polymer. In principle this technique is adaptable for in-line process monitoring.
Super-toughed Poly(lactic acid)/thermoplastic Poly(ether)urethane nanofiber composites with in-situ formation of aligned nanofibers prepared by an innovative eccentric rotor extruder Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-09 Yue He, Zhi-tao Yang, Jin-ping Qu
Large improvement of thermal transport and mechanical performance of polyvinyl alcohol composites based on interface enhanced by SiO2 nanoparticle- modified-hexagonal boron nitride Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-07 Jun Zhang, Chaowei Li, Cuiping Yu, Xiaona Wang, Qiulong Li, Huifen Lu, Qichong Zhang, Jingxin Zhao, E. Songfeng, Ming Hu, Yagang Yao
The interface plays a key role in determining the properties of polymer composites. However, chemical inertness of hexagonal boron nitride (h-BN) makes its surface modification troublesome. In this study, we, for the first time, used SiO2 as the modified molecular and investigated the effects of exfoliated h-BN and SiO2 nanoparticles-modified-exfoliated h-BN (SiO2@exfoliated h-BN) on the storage modulus, the glass transition temperature, the filler dispersion and the thermal conductivity of polyvinyl alcohol (PVA) composites prepared by a solution mixture method. The results showed that the SiO2 modification enhanced the interface interaction and improved the performance of the PVA composites. Based on the enhanced interface interaction by SiO2 modification and the aligned fillers in PVA by vacuum filtration, the high thermal conductivity of 13.88 W/m·K was realized at 15.2 wt% SiO2@exfoliated h-BN loading. Meanwhile, the tensile strength was also largely improved to 156 MPa, compared with 47 MPa of pure PVA. This study broadens the surface modification method of h-BN and provides a valuable reference for fabrication of high-performance thermal interface materials.
The effect of graphene network formation on the electrical, mechanical, and multifunctional properties of graphene/epoxy nanocomposites Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-08 Arnaud Kernin, Kening Wan, Yi Liu, Xuetao Shi, Jie Kong, Emiliano Bilotti, Ton Peijs, Han Zhang
The network formation of reduced graphene oxide (rGO) within an epoxy resin during the curing process has been in-situ visualised for the first time, with its effect on electrical, mechanical, and multifunctional properties of these nanocomposites explored. Different initial states of dispersion and filler contents were employed to examine the nanofiller network formation process. Good electrical conductivity (10−3 S/m at 0.05 wt% rGO) together with good mechanical reinforcement (12% increase in flexural modulus at 0.2 wt% rGO) were obtained at relatively low filler loadings. The integrated strain sensing capabilities based on the rGO network were explored with good sensitivity and repeatability. Joule heating was performed as a potential application for de-icing of multifunctional composite components with good heating capability from −20 °C to 20 °C within 2 min.
Novel electrically conductive epoxy/reduced graphite oxide/silica hollow microspheres adhesives with enhanced lap shear strength and thermal conductivity Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-07 Ruchi Aradhana, Smita Mohanty, Sanjay Kumar Nayak
Effect of ionomer interfacial compatibilization on highly filled HDPE/Al2O3/ionomer composites: Morphology and rheological behavior Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-05 Xin Chen, Jin Sha, Tao Chen, Haili Zhao, Huajian Ji, Linsheng Xie, Yulu Ma
Highly filled high-density polyethylene/alumina (HDPE/Al2O3) composites were fabricated by melt mixing with direct incorporation of poly(ethylene-co-methacrylic)-based ionomer (EMAA-Na) as an interfacial compatibilizer. SEM and EDX micrographs indicate EMAA-Na interfacial adhesion on the Al2O3 spheres. Under low EMAA-Na content conditions, the FT-IR characterization and an EMAA-Na neutralization degree analysis revealed the priority of the melt neutralization interaction between the acid groups of the ionomer and the Al2O3 spheres in the composite. Under high EMAA-Na content conditions, an AFM phase characterization revealed the formation of an EMAA-Na ionomer spherical domain (∼300 nm) dispersed in an HDPE matrix due to the microphase separation of ionic chains. Capillary and dynamic rheology measurements were also conducted to investigate the phase morphology evolution. The polymeric adhesion on the Al2O3 sphere surfaces contributed to the increase of the melt viscosity and gradual elongation thickening behavior of the composite melts. The formed spherical domain structure of EMAA-Na of the composite melts contributed to the shear thickening, elongation thickening and yield behavior. Three rheology criteria plots indicate large complex formation in the composite melts. The EMAA-Na incorporation in the highly filled HDPE/Al2O3 composite matrix not only improved the strength and toughness performance, with a 27% improvement in the elongation at break (EMAA-Na content 1 wt.%) and 21% improvement in the tensile strength (EMAA-Na content 10 wt.%), but also preserved the good thermal conductivity (∼1.5 W/(m·K)). This study reveals the potential application of the EMAA-Na ionomer to resolve the challenge of the strength and toughness performance degradation in highly filled polymer composites.
A novel and facile fabrication of polyphosphazene nanotube/carbon fiber multi-scale hybrid reinforcement and its enhancing effect on the interfacial properties of epoxy composites Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-02 Xiang Chen, Haibing Xu, Dong Liu, Chun Yan, Yingdan Zhu
The mechanical properties of carbon fiber (CF) reinforced composites are greatly dependent on the interfacial adhesion between fiber and resin matrix. Introducing nanoscale reinforcements into the interface is an effective approach to improve the interfacial adhesion of CF composites. In this paper, we proposed a facile and effective method for assembling poly(cyclotriphosphazene-co-4,4′-sulfonyldiphonel) nanotube onto CF surface as a novel multi-scale hybrid reinforcement through in situ template polymerization. The effects of surface modification on the surface and interface properties of CF and the resulting composite were investigated. After modification, the interfacial shear strength of fiber reinforced epoxy composites showed an increase of 26.4%. The reinforcing mechanisms were also analyzed, and the improvements on interfacial properties should mainly be attributed to mechanical interlocking effect. In addition, the modification even improved the fiber tensile strength by 6.6–16.3%, rather than deteriorating it.
Effects of state of charge on elastic properties of 3D structural battery composites Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-02 David Carlstedt, Erik Marklund, Leif E. Asp
The effects of state of charge (SOC) on the elastic properties of 3D structural battery composites are studied. An analytical model based on micromechanical models is developed to estimate the effective elastic properties of 3D structural battery composite laminae at different SOC. A parametric study is performed to evaluate how different design parameters such as volume fraction of active materials, stiffness of constituents, type of positive electrode material, etc. affect the moduli of the composite lamina for extremes in SOC. Critical parameters and configurations resulting in large variations in elastic properties due to change in SOC are identified. As the extreme cases are of primary interest in structural design, the effective elastic properties are only estimated for the electrochemical states corresponding to discharged (SOC = 0) and fully charged (SOC = 1) battery. The change in SOC is simulated by varying the volume and elastic properties of the constituents based on data from literature. Parametric finite element (FE) models for square and hexagonal fibre packing arrangements are also analysed in the commercial FE software COMSOL and used to validate the analytical model. The present study shows that the transverse elastic properties E 2 and G 23 and the in-plane shear modulus G 12 are strongly affected by the SOC while the longitudinal stiffness E 1 is not. Fibre volume fraction and the properties of the coating (such as stiffness and Poisson's ratio) are identified as critical parameters that have significant impact on the effect of SOC on the effective elastic properties of the composite lamina. For configurations with fibre volume fraction V f ≥ 0.4 and Young's modulus of the coating of 1 GPa or higher, the transverse properties E 2 and G 23 change more than 30% between extremes in SOC. Furthermore, for configurations with high volume fractions of electrode materials and coating properties approaching those of rubber the predicted change in transverse stiffness E 2 is as high as +43%. This shows that it is crucial to take effects of SOC on the elastic properties into account when designing 3D structural battery composite components.
Effect of graphene and fabrication technique on the release kinetics of carvacrol from polylactic acid Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-03 Roberto Scaffaro, Andrea Maio, Francesco Lopresti
Porous membranes and thin films containing poly-lactic acid (PLA), carvacrol (CRV) and graphene nanoplatelets (GNP) were fabricated by electrospinning and solvent casting at different formulations. The systems were characterized from a mechanical, morphological, calorimetric and spectroscopic point of view. CRV release as a function of time was studied and a mathematical model was used to fit and interpret the data in order to investigate the release mechanism. The results indicate that the incorporation of GNP generally determined a simultaneous strengthening, stiffening and toughening effect, while preserving a good ductility. Furthermore, integrating GNP allowed tuning the amount and kinetics of CRV release, and proved to reduce the initial burst release effect.
A phase-field model for strength and fracture analyses of fiber-reinforced composites Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-11-01 J.J. Espadas-Escalante, N.P. van Dijk, P. Isaksson
Enhancement of mechanical properties of CFRP manufactured by using electro-activated deposition resin molding method with the application of CNF without hydrophobic treatment Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-10-28 Kazuaki Katagiri, Katsuhiko Sasaki, Shinya Honda, Sayaka Minami, Shimpei Yamaguchi, Takuya Ehiro, Tomoatsu Ozaki, Hirosuke Sonomura, Sonomi Kawakita, Sohei Uchida, Masayuki Nezu, Yayoi Yoshioka
Cellulose nanofiber (CNF) is high strength and lightweight, additionally, it is produced by sustainable natural resources such as wood. Therefore, it has been reported the mechanical properties of CFRP can be improved by dispersing CNF in the matrix. However, as CNF is hydrophilic, a hydrophobic treatment was applied in many previous studies. For efficient CFRP manufacturing, the authors have developed an electrochemical resin molding method by using aqueous electro-activated deposition which contains the polymer having an epoxy group. In this method, the carbon fiber fabric is immersed in the electro-activated deposition solution and energized, epoxy resin is precipitated around the carbon fiber and impregnated. In this study, shortly after electro-activated deposition, CNF without a hydrophobic treatment was applied to the surface of the resin-impregnated carbon fiber fabric. The mechanical properties of CFRP could be enhanced, and optimum weight fraction of CNF was revealed.
Effect of surface modification on the dispersion, rheological behavior, crystallization kinetics, and foaming ability of polypropylene/cellulose nanofiber nanocomposites Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-10-29 Long Wang, Kiyomi Okada, Minami Sodenaga, Yuta Hikima, Masahiro Ohshima, Takafumi Sekiguchi, Hiroyuki Yano
Herein, the issue of dispersing cellulose nanofiber (CNF) in hydrophobic polymer has been solved through the modification of the CNF surface using alkenyl succinic anhydride (ASA). Polypropylene (PP) nanocomposites containing CNF with various degrees of substitution (DS)−ranging from 0 to 0.4−were prepared by melting and blending in an extruder. Fourier transform infrared spectroscopy (FTIR) results illustrated that the ASA chains were successfully incorporated into the CNF, and the FTIR spectroscopic imaging and X-ray computed tomography demonstrated the well-dispersed hydrophobic-modified CNF with the highest DS (=0.4) in the PP matrix. Rheological results revealed that a network-like structure of CNF was generated in the PP/CNF nanocomposites. Compared with isotactic PP, the PP/CNF composites exhibited improved crystallization kinetics, which could be elucidated via fast scanning chip calorimetry (FSC) analysis. Finally, the foaming performance of the prepared composites was examined using an easily scaled foam injection molding technique. The incorporation of CNF remarkably ameliorated the cellular morphologies of PP foams, resulting in a sharp decrease in cell size and a notable enhancement in cell density.
Highly conductive and stretchable fiber interconnections using dry-spun carbon nanotube fibers modified with ionic liquid/poly(vinylidene fluoride) copolymer composite Compos. Sci. Technol. (IF 5.16) Pub Date : 2018-10-29 Jimi Eom, Yu Ri Lee, Jun Ho Lee, Sung Kyu Park, Youngjin Jeong, Jong S. Park, Yong-Hoon Kim
In this paper, we demonstrate highly conductive and stretchable fiber interconnections for electronic textiles (e-textiles) using dry-spun carbon nanotube (CNT) fibers modified with ionic liquid (IL)/poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) copolymer composite. By adopting direct infiltration of CNT fibers with a mixture of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and PVDF-HFP, mechanical properties such as stretchability, maximum load and strain were significantly improved while minimizing the reduction in electrical conductivity. Such IL/PVDF modified CNT fibers (hybrid CNT fibers) exhibited electrical conductivity up to ∼1300 S/cm, with maximum load and strain values of 0.84 N and 35.7%, respectively. Using hybrid-CNT fibers, we demonstrated highly stretchable and electrically stable fiber interconnections for e-textiles by optimizing the interconnection pattern design. Particularly, by adopting a serpentine pattern, stretchability up to ∼70% and resistance variation of ∼2.7% at a tensile strain of 40% were achieved.
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