On the fracture behaviour of CFRP bonded joints under mode I loading: Effect of supporting carrier and interface contamination Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-20 Simon Heide-Jørgensen, S. Teixeira de Freitas, Michal K. Budzik
This paper addresses the fracture behaviour of bonded composite plates featuring a kissing bond along the crack growth path. Double cantilever beam (DCB) experiments are carried out under a displacement controlled loading condition to acquire the load response. The experimental data are collected and analysed analytically for specimens with and without kissing bond. The following aspects are observed and discussed: effect of the adhesive carrier film, non-smooth crack growth and rising R R curve. An analytical model taking into account the aforementioned effects is proposed. The kissing bond leads to unstable crack growth resulting in a loss of the load carrying capacity. The presence of the knit carrier in the adhesive film results in the crack growth process characteristic for the stick-slip phenomena and a significant increase of the resistance to fracture of the bondline by triggering a bridging phenomenon. The model shows a very good agreement with the experimental data. A sound understanding of the fracture process is gained enabling analysis and prediction of the effects of kissing bonds and supporting carrier.
POSS grafted hybrid-fabric composites with a biomimic middle layer for simultaneously improved UV resistance and tribological properties Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-19 Junya Yuan, Zhaozhu Zhang, Mingming Yang, Wenjing Wang, Xuehu Men, Weimin Liu
Poor interfacial adhesion and inferior UV resistance severely inhibit the development of hybrid Meta-aramid/Polytetrafluoroethylene (Nomex/PTFE) fabric composites for distinguished solid self-lubrication materials, especially under high exterior load and long-term UV irradiation conditions. Herein, glycidyl polyhedral oligomeric silesquioxanes (POSS) nanoparticles are covalently grafted onto the hybrid Nomex/PTFE fabric with a polydopamine/polyethylenimine (PDA/PEI) intermediate layer. The microstructure and chemical characteristics of Nomex and PTFE fibers before and after modification are investigated and the results manifest an obvious increase in surface functional groups and roughness, as well as resin compatibility. Tensile and peeling testing results show that the obtained fabric composites, denoted as hybrid-fabric@PDA/PEI-POSS composites, exhibit 24.3% and 46.8% enhancements in tensile and interfacial bonding strength without discernable decrease in pristine hybrid-fabric strength. In addition, the PDA/PEI-POSS hierarchical coating imparts the hybrid-fabric with excellent UV-shielding properties. As a result, the tribological performance of hybrid-fabric@PDA/PEI-POSS composites presents an obvious improvement under high load and UV irradiation conditions.
Crossed investigation of damage in composites with embedded quantum resistive strain sensors (sQRS), acoustic emission (AE) and digital image correlation (DIC) Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-19 S.N. Chowdhury, H. Bellégou, I. Pillin, M. Castro, P. Longrais, J.F. Feller
In a previous paper, we had evidenced that the memory effect of the resistance of embedded quantum resistive strain sensors (sQRS) could be used to quantitatively assess the damage accumulation in glass fibre reinforced polymers (GFRP). In this work, to comfort this finding and to better understand the mechanisms making sQRS able to monitor the composite's damage, three techniques have been combined to look for correlations during incremental cyclic tensile tests. Experiments were performed on composite samples of different typologies, all instrumented with sQRS in their core. The strain profile measured in the vicinity of defects such as a hole or a notch by digital image correlation (DIC), has been used to determine the strain profile to which the percolated carbon nanotube network based resistive sensors (sQRS) were exposed. Further on, acoustic emission (AE) counts were used to identify the strain level over which damages were recorded to interpret the events detected on the piezo-resistive trace of sQRS, i.e., matrix fracture, interface decohesion, fibres breakage. It is found that sQRS, through the variation of their apparent gauge factor GF, are able to detect strain concentration in their surroundings and to identify damage events in the composite, provided that the fracture behaviour has been previously analysed by AE. Finally, sQRS can keep the memory of the damage accumulated in the composite as their initial resistance shift monitors the non-reversible events associated to damage. Their implementation in composite structures should offer interesting prospects to secure their use by helping to locate stress/strain singularities and potentially anticipate the complete failure.
Fluid diffusion in cracked composite laminates – Analytical, numerical and experimental study Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-19 Abedin Gagani, Andreas T. Echtermeyer
Composite structural components are often subjected to service loads that cause cracks in off-axis layers, without compromising the load bearing capability of the structure. In marine or humid environments fluid ingress in the material can be accelerated by the presence of such cracks, leading to further strength degradation. Several studies have been dealing with the effect of cracks on fluid diffusion in composites, sometimes with contradictory results. In this work the difference between cracks on the external and internal plies of the laminate has been addressed both experimentally and analytically, showing that the first ones have a strong influence on diffusivity, while the second have a negligible effect.
Concurrent improvements in crosslinking degree and interfacial adhesion of hemp fibers reinforced acrylated epoxidized soybean oil composites Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-17 Wendi Liu, Ming-en Fei, Yang Ban, Anming Jia, Renhui Qiu, Jianhui Qiu
Rapid quantitative mapping of multi-walled carbon nanotube concentration in nanocomposites Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-16 Sandra J. Fisher, Milo S.P. Shaffer
Inhomogeneous distributions of nanoparticles in polymer nanocomposites have a strong influence on final material properties. Quantitative methods to characterise particle dispersion are rarely applied but are critical for advancing understanding of material behaviour, developing accurate computer models, and optimizing processing. Two complementary quantitative methods were developed to map local concentration, based on Raman spectroscopy and simple optical absorbance, respectively. The approaches are demonstrated for a model multi-walled carbon nanotube (MWNT) epoxy nanocomposite, but should be widely applicable. Maps of absolute concentration can be produced with submicron resolution, allowing analysis of the uniformity of MWNT concentration distribution via the coefficient of variation. The two approaches correlate closely, providing validation of both methods. However, the optical absorbance approach is likely to be more practical, in most cases, as it uses a standard laboratory microscope to analyse large areas rapidly.
Mechanical properties of polypropylene composites reinforced by hydrolyzed and microfibrillated Kevlar fibers Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-15 Sirui Fu, Bowen Yu, Wei Tang, Mao Fan, Feng Chen, Qiang Fu
As a traditional general plastic, polypropylene (PP) has been widely used in daily life. Glass fibers are often used to further reinforce the properties of PP for its application in engineering area. However, there are still some drawbacks existing for glass fibers filled polypropylene composites, such as high filler content, easy fracture of glass fibers and damage to the machines during processing. Therefore, organic fibers are considered as an ideal candidate to replace glass fibers. In this work, short Kevlar fibers (KFs) modified by ball milling in phosphoric acid and surface hydrolyzation were introduced to PP matrix to improve the interfacial interaction and mechanical properties. It is found that KFs were exfoliated into several flaky microfibers and then broken into pieces during the ball milling process. With the aid of phosphoric acid, the KFs can be split further thereby increasing specific surface area greatly. Then the original and milled KFs were hydrolyzed by NaOH aqueous solution in order to introduce OH group on the surface of KFs. The dispersion and mechanical properties of PP reinforced with various KFs, including original, ball milled, and hydrolyzed, were investigated and compared. It was found that the combination of ball milling in phosphoric acid and surface hydrolyzation is the most effective way for enhancement of interfacial reaction and mechanical properties. Adding 10 wt. % of KFs could lead to an increase of tensile strength of PP from 30 MPa to 47 MPa, which only can be achieved by adding at least of 25 wt. % of glass fibers. The tensile test shows that hydrolyze of KFs surface are a more important factor to promote the interfacial interaction between fibers and matrix. Our work demonstrates that PP can be enhanced efficiently by the introduction of hydrolyzed and microfibrillated KFs. Although KFs are expensive compared with glass fiber at this moment, their high reinforcement efficiency and toughness could make them competitive as reinforcing filler for the preparation of advanced polymer composites with excellent mechanical and processing properties.
A novel category of 3D chiral material with negative Poisson's ratio Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-15 Minghui Fu, Fengming Liu, Lingling Hu
A new design thought for 3D auxetic material is proposed based on the rotaion mechanism of chiral honeycombs. Two kinds of cell shape of the 3D auxetic material are studied as example, which are developed from the tetrachiral honeycombs with circular loops and square loops, respectively, with inclined rods connecting the neighbor layers. By replacing the tetrachiral honeycomb layers by other chiral honeycombs, such as trichiral, hexachiral honeycombs, other kinds of 3D chiral material with negative Poisson's ratio can be obtained. Moreover, since the cells' deformation of the 3D material is dominated by that of ligaments and rods under small deformation, the elastic properties of the 3D auxetic material are almost independent of the loops' shape. Thus, the loop can be designed to any shape instead of the traditional circular loop in order to obtain priory mechanical properties under large deformation. Based on beam theory and micromechanical method, the analytical formulas of both the elastic mudulus and Poisson's ratio are deduced for this category of 3D chiral material, which are verified by numerical simulations but also the experiment of 3D printed model. The verification results indicate that the formulas have higher precision and wider application scope. The influence of layer space on the equivalent parameters and the conditions for isotropic realization are discussed base on the analytical formulas. By changing the oblique direction of the inclined rods, another new 3D material can be obtained with positive Poisson's ratio in two directions and negative Poisson's ratio in the other one direction, for which the analytical formulas are still applicable.
Multi-functional interface tailoring for enhancing thermal conductivity, flame retardancy and dynamic mechanical property of epoxy/Al2O3 composites Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-15 Yuezhan Feng, Chengen He, Yingfeng Wen, Xingping Zhou, Xiaolin Xie, Yunsheng Ye, Yiu-Wing Mai
Interfacial tailoring is always the key to preparing high-performance polymer-based thermal conductive composites (PTCs). Herein, we reported a multi-functional interface tailoring approach to simultaneously improve the thermal conductivity, flame retardancy, thermal and mechanical properties of PTCs, by forming a core-shell structured graphene oxide coating Al2O3 hybrid (Al2O3@HGO). Simultaneously a flame retardant bridging agent was introduced to improve the coating amount and flame retardant efficiency of the hybrid. The morphology analysis revealed the significant reinforcement of interfacial interaction of Al2O3 in epoxy (EP) by HGO coating. As a result, such the interfacial tailoring induced both the significant decrease in interfacial thermal resistance and the formation of additional thermal conductive paths by the graphene coating layer, resulting in the significant improvement in thermal conductivity of EP/Al2O3@HGO composites. The flame retardant parameters, peak heat release rate, total heat release and total smoke production, showed a 49.3%, 40.9% and 71.2% reduction, respectively, comparing to neat EP, which was ascribed to the strong interface with GO coating layer and the flame retardant bridging agent catalyzed charring to form an intact and compact char protective layer with Al2O3. Moreover, the strong interfacial interaction also restricted the segment movement, increasing the storage modulus and Tg.
Mesoscopic modeling of the uniaxial compression and recovery of vertically aligned carbon nanotube forests Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-14 Bernard K. Wittmaack, Alexey N. Volkov, Leonid V. Zhigilei
Vertically aligned carbon nanotube (VACNT) arrays or “forests” represent a promising class of mechanically strong and resilient lightweight materials, capable of supporting large reversible deformation and absorbing mechanical energy. The mechanical response of VACNT forests to uniaxial compression is defined by various factors, including the material microstructure, its density, height, rate of deformation, and the nature of interaction between carbon nanotubes (CNTs) and the compressing indenter. In this paper, we use a coarse-grained mesoscopic model to simulate the uniaxial compression of VACNT samples with different densities and microstructures (bundle size distribution and degree of nanotube alignment) to obtain a clear microscopic picture of the structural changes in networks of interconnected CNT bundles undergoing mechanical deformation. The key factors responsible for the coordinated buckling of CNTs, reversible and irreversible modes of deformation for VACNTs undergoing uniaxial compression, as well as hysteresis behavior in VACNT arrays subjected to five loading–unloading cycles are investigated in the simulations. The simulation results reveal the important role of the collective buckling of CNTs across bundle cross-sections as well as a complex deformation behavior of VACNT arrays defined by an interplay of different modes of bundle deformation. The loading rate and the CNT attachment to the indenter are found to have a strong effect on the deformation mechanisms and the overall mechanical behavior of VACNT forests. A good agreement with experimental data from in situ mechanical tests is observed for general trends and magnitudes of loss coefficients predicted in the simulations. The forest morphology can strongly alter the mechanical behavior of VACNT arrays with nominally the same general characteristics, such as CNT radius, length, and material density, thus suggesting the opportunity for substantial enhancement of the mechanical properties through the microstructure modification.
Compact, flexible conducting polymer/graphene nanocomposites for high volumetric supercapacitors Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-14 Mahmoud Moussa, Maher F. El-Kady, Safwat Abdel-Azeim, Richard B. Kaner, Peter Majewski, Jun Ma
Graphene is extensively utilized in energy storage devices because of its high surface area and electron conductivity as well as ease of electrode fabrication. But graphene sheets often stack themselves in polymeric matrices leading to poor capacitive performance. This problem was addressed in this study by developing and inserting respectively two types of nano-sized conducting polymers into graphene interlayer spacing. The resulting hydrogel composite electrodes demonstrated efficient electron transfer for fast and reversible Faradaic reactions at the interface. Theoretical modelling by the density functional theory suggested that the reduction involve 2H+ transfer steps from polyaniline to graphene oxide: the first step would be an epoxy-ring opening process after activation of the C–O bond, and the second step would be C–O rupture leading to a de-epoxidation process. This binder-free electrode demonstrated high cycling performance and ultrahigh volumetric capacitance 612 F cm−3, being 10 times higher than the activated carbon used in the current industry. The study represents a step forward towards the fabrication of flexible, high-energy density supercapacitors.
Grafting carbon nanotubes onto carbon fibres doubles their effective strength and the toughness of the composite Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-14 Luca Lavagna, Daniele Massella, Maria F. Pantano, Federico Bosia, Nicola M. Pugno, Matteo Pavese
Bioinspiration can lead to exceptional mechanical properties in a number of biological materials as a result of their internal structure. In particular, the hierarchical arrangement of nano-to macro-components can bring to complex energy dissipation mechanisms and unprecedented resistance to crack growth. In this work, we propose to exploit this approach, combining in a multiscale composite structure carbon nanotubes with conventional carbon fibre reinforcements in a polyvinyl butyral matrix. We show that grafting the nanotubes onto the carbon microfibres improves their interface properties with the matrix considerably, effectively doubling their apparent strength. At the same time, the addition of nanotubes to microfibre reinforcements helps to improve the composite toughness, reaching more than twice the value for the conventional, non-hierarchically reinforced composite. Numerical simulations and fracture mechanics considerations are also provided to interpret the results.
The mechanism for the temperature-dependency of the interfacial interaction in polyamide/tin-fluoro-phosphate glass composites Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-13 Huan Li, Xiaomeng Zhang, Jianfeng Wang, Chunhai Li, Shuai Liu, Hong Wu, Shaoyun Guo
The interfacial interaction in polyamide/tin-fluoro-phosphate glass (TFP-glass) composites exhibits a positive correlation with temperature, whose mechanism is still unknown. The thermal-induced dissociation behavior at 232 °C of TFP-glass, which has been observed and investigated in our previous works, provides a plausible mechanism for the temperature-dependency of the interfacial interaction. In this work, the influence of the dissociation degree, which is controlled by processing temperature, on the interfacial interaction between TFP-glass and copolymerized 6/66 copolymer (cPA) is investigated. Three processing temperatures, 215, 230, and 245 °C (below, around and above the dissociation temperature of TFP-glass, Td = 232 °C), are chosen to prepare cPA/TFP-glass composites. With increasing the degree of dissociation, improved dispersion of TFP-glass particles in polymer matrix and enhanced interconnection between the two components are observed, indicating that the interfacial interaction in cPA/TFP-glass composites is gradually enhanced. The dielectric relaxation spectra, which can probe the local motions of macromolecular fragments at different length scales, are used to investigate the influence of the dissociation degree on the length scale of the interfacial interaction in cPA/TFP-glass composites. The improved thermal stability of cPA/TFP-glass composites filled with the same content of TFP-glass also confirms the enhancement of the interfacial interaction. Therefore, conclusions can be drawn that the dissociation behavior of TFP-glass is contributed to the temperature-dependency of the interfacial interaction in polyamide/TFP-glass composites. The work reported in this paper should provide theoretical guidance for taking advantage of this positive correlation with temperature of the interfacial interaction and help us to deeply understand the mechanism for the interfacial interaction in TFP-glass filled composites.
Protein-mediated interfacial adhesion in composites of cellulose nanofibrils and polylactide: Enhanced toughness towards material development Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-12 Alexey Khakalo, Ilari Filpponen, Orlando J. Rojas
The role of animal protein, casein, as compatibilizer and eco-friendly dispersant in composites comprising cellulose nanofibrils (CNF) and polylactic acid (PLA) was investigated. The effect of casein-mediated surface modification of PLA was validated with dynamic adhesion experiments that considered the contact area according to JKR approximation. In fact, a remarkable increase by ∼50% in the work of adhesion between CNF and PLA was observed after casein adsorption. It is likely that the improved adhesion gave rise to an enhanced dispersion of CNF and PLA within the composite matrix. Moreover, the mechanical properties of the respective nanocomposites were significantly improved. When compared to protein-free CNF/PLA nanocomposites, the systems containing casein indicated an enhanced extensibility (by 130%) and tensile toughness (by 60%) whereas tensile strength and Young's modulus were improved to a limited extent (6 and 12%, respectively). Finally, it is demonstrated that the surface modification of PLA with casein improves the compatibility between CNF and PLA, which is a prerequisite for the feasible preparation of 3D shaped cellulose-based packaging materials by direct thermoforming.
A transparent pressure-sensitive adhesive with high electrical conductivity based on water-soluble nano core-shell hollow composite Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-12 Lipei Yue, Xiaoyong Zhang, Weidong Li, Yongping Bai, Yudong Huang
The transparent conductive pressure sensitive adhesives (PSAs) are increasingly used for demanding applications, such as interconnects in electronic assemblies and transparent conductive films. Graphene is an efficient modifier for highly conductive PSAs, but it is hard to prepare homogenous composite and the transparency of PSA is bad, moreover, there is increased contact resistance during elevated temperature and humidity. In this work, we report a water-soluble core-shell hollow composite using graphene oxide (GO) modified by acrylamide as core through in situ polymerization. The composite is homogenous without any aggregation after testing in normal temperature for 100 days. The light transmittance of the PSA based on polyethylene terephthalate film is above 90% if the content of GO in the composite is under 0.2 wt%. The electrical conductivity of the PSA increases from 0.29 Sm-1 to 0.62 Sm-1 while the related humidity ranges from 0% to 90%. PSA film formed by core-shell composite can hold hydrone and exhibit advanced electrical conductivity in high humidity atmosphere. The conductivity of the composite is stable and unchanged in high temperature.
Multiscale multiphysical analysis of photo-mechanical properties of interphase in light-responsive polymer nanocomposites Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-10 Joonmyung Choi, Hyunseong Shin, Maenghyo Cho
The design of the adaptive mechanical behavior of polymer nanocomposites driven by light irradiation has attracted considerable attention in the fields of physical chemistry and mechanical engineering. To assess the photo-mechanical properties of photo-responsive polymer (PRP) nanocomposites reinforced with gold nanoparticles via continuum mechanics, we first investigated interfacial properties of PRP nanocomposites by using a novel multiscale multiphysical model. Particularly, the interfacial interactions between the nanoparticle and polymer matrix under external loading were addressed by combining all-atom molecular dynamics (MD) simulations with finite element (FE) analysis. To explicitly characterize the role of the interfacial interactions between the nanoparticle and polymer matrix in strain energy density under photo-mechanical loading, the effective stiffness and the spatial range of the interphase layer were numerically identified by matching the deformation energy in the FE model with that in the MD model using the energy method and the homogenization theory. It is verified that the equivalent continuum model obtained by the multiscale method satisfactorily predicts not only the overall mechanical properties of nanocomposites, but also the local stress distribution at the interphase as well as the inherent nanoparticle size and photo-isomerization reaction effects of the nanocomposites. The present multiscale analysis reveals that the effective interfacial region around the nanoparticle is considerably weakened as the photo-isomerization reaction progresses, as well as the decrease of the thickness of the interfacial region.
Micromechanical study on the influence of scale effect in the first stage of damage in composites Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-09 Federico París, María Luisa Velasco, Elena Correa
The variation in the apparent strength of a lamina in a laminate depending on the stacking sequence and thicknesses of the laminas of the laminate has been a matter of interest since the initiation of the extension of the applicability of composites. This fact led to the concept of in-situ strength, the problem itself being covered as a scale effect. In this paper this question is revisited moving towards the level where the damage appears, that is the micromechanical level. As the origin of the effect under consideration, the variation of thickness, takes place at a different level (mesomechanical), a multi-scale model is developed. It is possible in this model to vary the thickness of the lamina under consideration and to observe its effect on the damage. In this paper, only the first stage of damage, which appears in form of debondings between fibres and matrix, is taken into consideration. The analysis carried out shows that there is no scale effect at this first stage of the damage, which is corroborated by experimental evidences.
Multiscale modeling of carbon fiber/carbon nanotube/epoxy hybrid composites: Comparison of epoxy matrices Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-09 M.S. Radue, G.M. Odegard
This study addresses the multiscale modeling of hybrid composites composed of carbon fibers (CFs), carbon nanotubes (CNTs), and three different epoxy systems (di-, tri-, and tetra-functional resin epoxies). Molecular dynamics (MD) simulations are performed to predict the molecular-level interfacial and mechanical behavior of CNT embedded in epoxy. Micromechanics calculations are implemented to translate the molecular phenomena observed to predict the mechanical properties of CNT/epoxy composites with randomly oriented CNTs and CF/CNT/epoxy systems with aligned CFs and randomly oriented CNTs. The model is validated with experimental Young's modulus values for CNT/epoxy available in the literature. The results demonstrate that the tri- and tetra-functional resin epoxies demonstrate comparably high moduli over the di-functional resin for CNT concentrations up to 5 wt%. For higher CNT loadings, the tri-functional resin epoxy is predicted to outperform the other resins with respect to stiffness due to its strong interaction with CNTs and high bulk stiffness.
High-strength epoxy nanocomposites for 3D printing Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-09 Nadim S. Hmeidat, James W. Kemp, Brett G. Compton
Clay-based nanoscale filler materials are commonly used to impart unique and desirable properties to polymer resins. Small volume fractions of nanoclay have disproportionately large effects on stiffness, toughness, strength, and gas barrier properties of polymer matrices due to their high surface-to-volume ratio and platelet morphology. Recent work has suggested that highly loaded epoxy/clay/fiber mixtures possess desirable rheological properties for use as feedstock materials for direct-write 3D printing, but little is known about the effects of the deposition process on the resulting properties of the printed composites. In this work we characterize the effects of a functionalized nanoclay on the rheological properties and printing behavior of an epoxy resin in the absence of fiber reinforcements, and investigate the effects of clay content and the deposition process on the thermo-mechanical properties of the resulting 3D-printed epoxy/clay nanocomposites. The rheological properties of ink formulations containing up to 12.5 wt% nanoclay are measured using parallel plate rheometry, and the thermo-mechanical properties of the printed composites are measured using 3-pt flexural testing, dynamic mechanical analysis, and thermo-gravimetric analysis. Flexural strength values range from 80 MPa to 100 MPa for cast samples and printed samples tested transverse to the printing direction, and up to 143 MPa for printed samples tested parallel to the print direction. Although the observed anisotropic strength values indicate that the deposition process does impart orientation to the nanoclay, the strength in each direction is significantly greater than values reported for 3D printed thermoplastic composites, suggesting that the epoxy/clay system has high potential for further development as a 3D printing feedstock material.
Intermittent beading in fiber composites Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-07 Israel Greenfeld, Wenyong Zhang, XiaoMeng Sui, H. Daniel Wagner
Simultaneous improvement of strength and toughness is a challenge in composite materials, as an improvement in one is generally at the expense of the other. The filler-matrix interface has a crucial role in such improvement. It appears that modification of the interfacial structure/geometry may have wider possibilities and benefits than the classical chemical bonding approach. Using a model glass-epoxy fiber-reinforced composite, we modified the regular cylindrical fiber-matrix interface by applying intermittent epoxy beads along the fiber, taking advantage of the Plateau-Rayleigh liquid instability phenomenon. Under load, the beads serve as fiber anchors in the matrix, thus exploiting the fiber strength to its maximum. During fracture, the pullout of beads through the matrix appears to dissipate more plastic deformation energy compared to the pullout of regular fibers. Fragmentation tests of beaded fibers in epoxy matrix demonstrate these failure mechanisms; single-bead fiber pullout tests with different bead sizes and surface treatments provide strength and toughness data that substantiate this approach. The concept of intermittent beading has ample possibilities for optimization. It is also scalable and therefore practical.
Shape memory behavior of liquid-crystalline/graphene oxide elastomer nanocomposites Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-06 Angela Marotta, Giuseppe Cesare Lama, Veronica Ambrogi, Pierfrancesco Cerruti, Marta Giamberini, Gennaro Gentile
Segregated polypropylene/cross-linked poly(ethylene-co-1-octene)/multi-walled carbon nanotube nanocomposites with low percolation threshold and dominated negative temperature coefficient effect: Towards electromagnetic interference shielding and thermistors Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-06 Yu-Fan Liu, La-Mei Feng, Yi-Fu Chen, Yu-Dong Shi, Xu-Dong Chen, Ming Wang
High-efficiently conductive networks have been well demonstrated to improve electrical properties of conductive polymer composites (CPCs). Here, a facile approach was introduced to control distribution of multi-walled carbon nanotubes (MWCNTs) in isotactic polypropylene/poly(ethylene-co-1-octene) blends (iPP/POE). The POE first melt-crosslinked by the addition of dicumyl peroxide, pulverized into small particles (40–60 meshes), then coated with iPP/MWCNTs composites, and finally compression molded to achieve the segregated iPP/POE/MWCNTs composites with MWCNTs confinedly dispersing in continuous iPP phase. This segregated structure could easily construct high-efficiently conductive networks, resulting in a low percolation threshold of 0.24 vol.%, high-performance electrical conductivity, and electromagnetic interference shielding effectiveness (EMI SE). For example, the EMI SE of ∼25 dB could be achieved in the segregated nanocomposites with 3.0 vol.% MWCNTs (thickness 1.2 mm) which reached the commercial requirement. Furthermore, the segregated samples also exhibited a relatively linear negative temperature coefficient (NTC) effect through wide temperature ranges of 45–120 °C and 150–190 °C because of anisotropic volume expansion effect caused by the segregated structure.
Multifunctional BiFeO3 composites: Absorption attenuation dominated effective electromagnetic interference shielding and electromagnetic absorption induced by multiple dielectric and magnetic relaxations Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-06 Yong Li, Ningning Sun, Jia Liu, Xihong Hao, Jinhua Du, Huijing Yang, Xiaowei Li, Maosheng Cao
BiFeO3 (BFO) grains prepared by molten salt method were fabricated in paraffin wax based composite structure to evaluate electromagnetic interference (EMI) shielding and electromagnetic (EM) absorption in 2–18 GHz. In the composites, BFO750 paraffin wax composite exhibits excellent EMI shielding and EM absorption performance. The EMI shielding effectiveness of BFO750 paraffin wax composite surpasses 10 dB, and its reflection loss shows three absorption peaks which reach −17 dB. The absorption efficiency and attenuation constant are close to 80% and 70, respectively. The results demonstrate that absorption attenuation is the dominant mechanism of EMI shielding and EM absorption. This is attributed to multiple dielectric and magnetic relaxations, where electric and magnetic dipoles coexisting in the composite can respond intensively to electromagnetic wave in the frequency range and thus cause high electromagnetic loss. The work highlights BFO composites as promising multifunctional materials in electromagnetic wave protection fields.
Construction and non-linear viscoelastic properties of nano-structure polymer bonded explosives filled with graphene Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-06 Congmei Lin, Guansong He, Jiahui Liu, Liping Pan, Shijun Liu, Jiang Li, Shaoyun Guo
The 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)-based polymer bonded explosives (PBXs) modified with different contents of graphene from 0.05 wt% to 0.5 wt% were prepared by the water suspension methods. The non-linear viscoelastic properties of the TATB-based PBXs were detailedly investigated. The experimental results indicated that with the incorporation of only a small amount of graphene, the storage modulus, the static mechanical properties, and creep resistance in the nanocomposites were effectively improved. A rigid filler effect and the strong sheet/polymer matrix interfacial interaction to restrict the mobility of polymer chains played an important role in the enhanced non-linear viscoelastic behaviors of nanostructured materials. The formation mechanisms were further interpreted based on the modeling of the creep behavior using a six-element mechanical model. The modeling results demonstrated that the introduction of the graphene into the TATB-based PBXs was an effective and fundamental method to enhance the elastic modulus of high elastic deformation and restrain the irrecoverable deformation of the materials. The long-term creep behaviors predicted using the time-temperature superposition principle revealed that PBXs with 0.15 wt% graphene exhibited a lowest long-term creep strain.
Poly(vinylidene fluoride)-Based composites modulated via multiscale two-dimensional fillers for high dielectric performances Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-06 Dalong He, Yao Wang, Lingyu Zhang, Silong Song, Yuan Deng
Ultrathin two-dimensional (2D) semiconductor molybdenum disulfide (MoS2) nanosheets have wide applications in electronic devices. Incorporation of MoS2 nanosheets into poly(vinylidene fluoride) (PVDF) renders a type of dielectric composite regulated with 2D architecture. However, due to the semiconducting behavior of MoS2, the accompanying high dielectric loss prevents the composite being good dielectrics. Aluminum flakes (AFs), another 2D structure in micron scale, were thus introduced into the MoS2/PVDF composite to block leakage path as well as providing another source for electric polarization. The effects of multiscale 2D fillers on adjusting the dielectric and electrical properties of the ternary MoS2/AFs/PVDF composites were investigated systematically. The largely suppressed dielectric loss and electrical conductivity of ternary composite compared with those of MoS2/PVDF composite is ascribed to the parallel arranged self-passivated AFs, which effectively inhibit the direct connection and overlapping of MoS2 nanosheets along the electric field direction. Meanwhile, formation of numerous micro-capacitors with AFs as electrodes and MoS2/PVDF composite as dielectric medium makes an additional contribution to the high dielectric constant of the ternary composite. Furthermore, the dielectric polarization and relaxation process of composites were investigated in terms of electric modulus to explain the variation tendency of dielectric and electric property of the composites.
Effects of carboxylated carbon nanotubes on the phase separation behaviour and fracture-mechanical properties of an epoxy/polysulfone blend Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-06 Nan Zheng, Weifu Sun, Hong-Yuan Liu, Yudong Huang, Jiefeng Gao, Yiu-Wing Mai
Epoxy resins are inherently brittle caused by their highly cross-linked network structure. Herein, we report an effective method of toughening without loss of mechanical properties. Carboxylated carbon nanotubes (CNT-COOHs) were added to an epoxy (EP)/polysulfone (PSF) blend to control the phase separation behavior, fracture toughness and mechanical properties of the resultant ternary composites. Although CNT-COOHs did not change the phase separation mechanism of the EP/PSF blend they had an important influence on the final phase morphology. Rheological analysis showed that the complex viscosity and the cure-reaction rate of EP/PSF were increased by adding CNT-COOHs, leading to a significant suppression of the phase separation process which stopped at an earlier stage. Also, the fracture, mechanical and thermal properties of the EP/PSF/CNT-COOH composites were found to be increased due to the presence of CNT-COOHs.
Fabrication of pristine graphene-based conductive polystyrene composites towards high performance and light-weight Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-05 Fangwei Zhao, Guangfa Zhang, Shuai Zhao, Jian Cui, Ailin Gao, Yehai Yan
Although highly electrically conductive polymer composites filled with two-dimensional graphene-based nanofillers have been considerably explored, it still remains a challenge for constructing these nanocomposites with high filler efficiency, mild fabricating condition, as well as more effective conductive network at lower nanofiller contents. To meet above objectives, a facile preparation strategy was designed, wherein the pristine graphene (pGR) was utilized as nanofiller in polystyrene (PS) particle matrix via latex technology. Owing to the absence of reduction process, the hot-processing parameters were optimized to be more gentle ones. The structural, morphological, electrical, thermal and mechanical properties of resultant PS/pGR nanocomposites with various pGR contents were systematically investigated. SEM and TEM images showed the excellent interfacial adhesion between these two materials and segregated conductive structure was well-established. The as-fabricated PS/pGR composites achieved a quite high electrical conductivity of 20.5 S/m at a relatively low pGR loading of 0.957 vol% and an ultralow electrical percolation threshold of 0.0475 vol%. The thermal conductivity (TC) increased by 2.1 times at 0.957 vol% pGR loading than neat PS and the mechanical properties also exhibited applaudable results. This novel strategy to fabricate high performance PS conductive composites based on pristine graphene as nanofillers was thus proved to be effective.
Strong process-structure interaction in stoveable Poly(Urethane-Urea) aligned carbon nanotube nanocomposites Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-03 Jeffrey L. Gair Jr., Robert H. Lambeth, Daniel P. Cole, Dale L. Lidston, Itai Y. Stein, Estelle Kalfon-Cohen, Alex J. Hsieh, Hugh A. Bruck, Mark L. Bundy, Brian L. Wardle
The exceptional static and dynamic physical properties of poly (urethane-urea) (PUU) elastomers make them prime candidates for impulsive loading structural applications, such as blast protection coatings. Since the theoretical physical properties of carbon nanotubes (CNTs) are among the best for any currently known material, a number of previous studies explored the use of CNTs as nanoscale fillers to enhance the properties of PUU nanocomposites. However, due to the challenges inherent in dispersing CNTs in a PUU matrix and the resulting random orientation of the CNTs, these previous works observed marginal improvements in physical properties, and were unable to establish clear structure-property relations. Here, we report the synthesis of aligned-CNT (A-CNT) reinforced PUU polymer nanocomposites (A-PNCs) by infusing A-CNT forests with a stoveable PUU, and establish process-structure-property relations that quantify the contribution of CNT confinement on the PUU mechanical response. This stoveable process was achieved using blocked isocyanate which prevented polymerization until the blocks were removed with heat. PUUs of two distinct compositions were explored: one with 40 wt% hard-segment content (PUU211) and the other with 66 wt% hard-segment content (PUU541). Thermogravimetric analysis indicates that A-CNTs enhance the thermal stability of the hard-segment phase in PUU A-PNCs at 340 °C by up to 45% over the baseline PUUs. Atomic force microscopy reveals that the nanophase hard-segment formations observed only in the nanocomposites were of similar characteristic size to the average inter-A-CNT spacing (∼70 nm), indicating a strong influence of A-CNTs on the size and orientation of hard-segment nanophases, as corroborated via small angle X-ray scattering. Nanoindentation testing reveals that/PUU A-PNCs possess significant elastic anisotropy, and exhibit enhanced longitudinal effective indentation moduli of ∼460 MPa (>3 × that of the PUU211 baseline) and ∼1350 MPa (∼1.5 × that of the PUU541 baseline) for PUU211 and PUU541 nanocomposites, respectively. This difference in magnitude of CNT reinforcement efficacy indicates that CNT confinement leads to significant hard-segment re-organization in the PUU211 A-PNCs, whereas the interconnected network of hard-segments in the PUU541 is affected by CNT templating to a lesser extent in the PUU541 A-PNCs. Dynamic nanoindentation testing results are consistent with these interpretations, where longitudinally-loaded PUU211 A-PNCs are found to exhibit a >3 × enhancement in storage modulus at 1 Hz of ∼730 MPa, whereas the longitudinally-loaded PUU541 A-PNCs exhibit a slightly enhanced storage modulus enhancement at 1 Hz of 2190 MPa (∼1.5 × that of the PUU541 baseline). Reinforcement of PUUs with A-CNTs is a promising way to tune the physical properties of PUUs; higher A-CNT packing densities, where the inter-CNT spacing could approach the nanophase characteristic diameter, could further enhance the PUU performance in ballistic protection applications.
Viscoelastic properties of a 3D-Printable high-dielectric paste with surface-modified BaTiO3 Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-03 Jae Yun Park, Yi Young Kang, Hyun Woo Yoon, No Kyun Park, Yejin Jo, Sunho Jeong, Jong Chan Won, Yun Ho Kim
In this study, a polystyrene-block-polyisoprene-block-polystyrene (SIS) based dielectric paste was fabricated using barium titanate (BT) as dielectric filler in order to produce organic-inorganic composites for 3D dispenser printing applications. Since a high loading of inorganic filler is generally required to obtain high dielectric properties, the surface of BT was modified with two different phosphonic acids having functional groups resembling the groups contained in the block copolymer, in order to achieve a high compatibility between the filler and the polymer matrix. Upon incorporation of 80 wt% of BT in SIS, the dielectric constant was found to be approximately 3 times higher than that of bare SIS. The surface modification of the filler enhanced its dispersion within the polymer matrix, as confirmed by the surface morphology of the composite film at a high filler content. The desired viscoelasticity was achieved through the fine-tuning of the total solid content, and consequently, the potential application of the composite as 3D printable paste was demonstrated through the formation of a layer-by-layer printed structure on a flexible substrate.
A bio-surfactant for defect control: Multifunctional gelatin coated MWCNTs for conductive epoxy nanocomposites Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-03 Yichao Li, Renfu Li, Xuewei Fu, Yu Wang, Wei-Hong Zhong
To simultaneously improve mechanical and electrical properties for polymers via addition of appropriate nanomaterials, such as carbon nanotubes (CNTs), can be realized only if an effective treatment method for CNTs is applied. Here, we report a study of using gelatin, an environmental friendly and abundant protein with rich functional groups, as a bio-surfactant to treat multi-walled carbon nanotubes (gelatin-CNTs) for fabricating multifunctional epoxy nanocomposites. The study results show that the gelatin-CNTs are more effective than a type of chemically treated CNTs for improving multifunctional properties of epoxy, in addition to the benefit to the environment by avoiding applying conventional acids for CNT treatment. In specific, gelatin treatment significantly improved dispersion of CNTs, wettability, conductivity and mechanical properties for epoxy, in comparison with that of pristine CNTs/epoxy and amino treated system, NH2-CNTs/epoxy. The electrical conductivity of the epoxy nanocomposite with 0.5wt% of gelatin-CNTs is two orders of magnitude higher than the NH2-CNTs/epoxy. The enhancement in the flexural modulus and strength of the 0.5wt% gelatin-CNTs/epoxy is much bigger than those of NH2-CNTs/epoxy. The mechanism that is responsible for such significant enhancement in multifunctional properties is analyzed. This research work provides a new green avenue to the fabrication of high performance multifunctional nano-modified epoxy matrix.
Random field generation of stochastically varying through the thickness permeability of a plain woven fabric Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-02 Min-young Yun, Pavel Simacek, Christophe Binetruy, Suresh Advani
In the Vacuum Assisted Resin Transfer Molding (VARTM) process to manufacture composites, woven or stitched fabrics are stacked on top of a tool surface and resin is introduced into this porous network by drawing a vacuum. For large parts, to reduce the time for filling, highly permeable distribution media (DM) is placed on top of the fabric layers to accelerate the in-plane filling process. Many factors such as the manufacturing process, handling, variation in fabric manufacturing and placement of fabric cause heterogeneity in the permeability of fibrous materials. Due to the presence of the DM, the heterogeneous through the thickness permeability (Kpin) of a fabric can dramatically affect the flow of resin and cause air pockets or voids which are mechanical flaws resulting in the rejection of the composite as scrap. Statistical characterization of Kpin is crucial for understanding the (i) effect of heterogeneity in Kpin and its interaction with DM permeability and void formation and (ii) for generating the field of random numbers (Kpin), which can be used for simulations to predict resin flow and void formation for such materials that exhibit stochastic variability. The novelty of this study is that the observed random field (Kpin) is generated for numerical simulation through statistical analysis. First, in this study, the heterogeneity in Kpin was statistically characterized by spatial correlation with Moran's I index and semi-variogram. Then the random field of Kpin was generated by transforming the normal numbers from Karhunen–Loève (KL) expansion to gamma numbers. A numerical flow simulation of the VARTM process with the generated random fields was performed using Monte Carlo method for three types of Distribution Media (DM). The outcome is compared with experimental results and to simulation results that used experimentally determined Kpin data as an input.
Electrically conductive PDMS-grafted CNTs-reinforced silicone elastomer Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-03-01 Junhua Kong, Yuejin Tong, Jiaotong Sun, Yuefan Wei, Warintorn Thitsartarn, Chee Chuan Yeo Jayven, Joseph Kinyanjui Muiruri, Siew Yee Wong, Chaobin He
Conductive liquid silicone rubber-based composites were prepared through incorporation of fumed silica (FSiO2) and polydimethylsiloxanes (PDMS) modified MWCNTs (P-MWCNTs), and their mechanical and electrical properties were investigated. It is shown that the introduction of P-MWCNTs with P-MWCNTs/FSiO2 ratio of 0.25/30 (w/w) increases the cross-linking density and the thermal stability of the composites significantly. The improved mechanical performance, e.g., 60% increase for Young's modulus and 47% increase for tear strength, should be ascribed to the stronger interfacial interaction between P-MWCNTs and PDMS matrix and better dispersion of P-MWCNTs due to existence of PDMS on CNT surface. Moreover, the better dispersion of P-MWCNTs also ensures much higher electrical conductivity than original carboxyl functionalized MWCNTs (COOH-MWCNTs) at relatively low loading, e.g., 10−3 S m−1 versus 10−8 S m−1 at MWCNTs/FSiO2 ratio of 2.5/30, which could be attributed to the formation of CNT network.
Investigation of the tensile behavior of treated flax fibre bio-composites at ambient humidity Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-27 D. Perremans, I. Verpoest, C. Dupont-Gillain, A.W. Van Vuure
The high specific strength and stiffness and excellent damping behavior promote the use of flax fibre composites in the construction sector. However, the limited compatibility between raw flax fibres and bio-epoxy resin often leads to composites with mechanical properties well below their theoretical capacities. Moreover, the incomplete understanding of the intrinsic non-linear mechanical behavior of flax fibre composites forces the application of larger safety factors. In this study, three chemical treatments are applied to improve the interphase properties and gain further insight in the longitudinal tensile behavior of flax fibre bio-epoxy composites. Both alkali and APS treatment result in a threefold improvement in the transverse flexural strength to ∼30MPa. Both treatments additionally shift the weakest link to the elementary fibre interphase strength. Analysis of the longitudinal tensile stress-strain curves of UD flax fibre composites results in a tri-linear shape that is preserved after treatment.
Facile and simple fabrication of strong, transparent and flexible aramid nanofibers/bacterial cellulose nanocomposite membranes Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-27 Yadong Wu, Fang Wang, Yudong Huang
Mechanical strength, transparency and flexibility are the leading bottlenecks for the application of a membrane. Thus, the development of co-effectively strong, transparent and flexible membranes is significant for various industries. Here, we fabricated the ANFs (aramid nanofibers)/BC (bacterial cellulose) nanocomposite membranes with different ANFs loadings (up to 8.0 wt%) via a facile and simple vacuum-assisted flocculation route. FT-IR, XRD and SEM were applied to characterize the pure BC membrane and ANFs/BC nanocomposite membranes. The resultant membranes maintained excellent transparency and flexibility at relatively low ANFs concentrations (≤4.0 wt%). The mechanical properties of ANFs/BC nanocomposite membranes could be altered by changing the ANFs content, in which the ANFs served as an enforcement agent, and the nanocomposite membrane exhibited the highest tensile strength at ANFs content of 4.0 wt%. Besides the excellent tensile strength, transparency and flexibility, the surface wettability of the ANFs/BC decreased compared to that of pristine BC, indicating a relative stability in humidity. These results showed that the ANFs/BC nanocomposite membrane is strong, transparent and flexible, thus making it an excellent candidate for electronic substrates and optical materials.
Enhancing interfacial shear strength via surface grafting of carbon fibers using the Kolbe decarboxylation reaction Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-27 Chantelle L. Arnold, Kathleen M. Beggs, Daniel J. Eyckens, Filip Stojcevski, Linden Servinis, Luke C. Henderson
The manufacture of carbon fibers includes an oxidative electrochemical process that represents an untapped source of potential surface manipulation beyond simple installation of oxygen containing functional groups. In this work we show that applying an oxidative treatment, at much lower oxidative potentials (+1.75 V) compared to industry standards, can result in simultaneous surface modification and oxidation resulting in substantial increases in interfacial shear strength, up to 112%, relative to pristine carbon fibers. The optimal treatment window for this process is 10 min, offering synergistic oxidation and surface grafting interactions with epoxy resin. This treatment is easily scalable, amenable to a continuous oxidation process, and can be adapted to existing infrastructure currently used in carbon fiber manufacture.
CNT and polyaniline based sensors for the detection of acid penetration in polymer composite Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-26 Chang Liu, Ivan Sergeichev, Iskander Akhatov, Khalid Lafdi
Today, polymer composites are used to store liquid chemicals. Monitoring their structural health is crucial. In this study, conductive nanocomposite-based sensors were designed to monitor acid penetration over time. The sensors were made using blends of epoxy resin and additives, such as polyaniline and carbon nanotube (CNT). It appeared that as the concentration of additives increased, the sensors' response time were shorter. The CNT-based nanocomposites had shown an especially high sensitivity. However, to track the acid penetration over time, polyaniline-based sensors seem more adequate. A simple kinetic model was developed to have a better understanding of sensor behavior.
Advanced carbon fiber composite out-of-autoclave laminate manufacture via nanostructured out-of-oven conductive curing Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-26 Jeonyoon Lee, Xinchen Ni, Frederick Daso, Xianghui Xiao, Dale King, Jose Sánchez Gómez, Tamara Blanco Varela, Seth S. Kessler, Brian L. Wardle
Next-generation composite manufacturing processes are needed to overcome several limitations of conventional manufacturing processes (e.g., high energy consumption). Here we explore, via experiments and modeling, the characteristics of the newly developed out-of-oven (OoO) curing technique that cures a composite laminate via resistive heating of a carbon nanotube film. When compared to oven curing of an aerospace-grade out-of-autoclave (OoA) carbon fiber prepreg advanced composite laminate, the OoO curing reduces energy consumption by over two orders of magnitude (14 vs. 0.1 MJ). Thermophysical and mechanical tests including differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), short beam shear, and ex-situ and in-situ double-edge notch tension indicate that the physical and mechanical properties of OoO-cured laminates are equivalent to those of oven-cured (baseline) laminates. In addition to energy savings, the OoO curing process has the potential to reduce part-to-part variations through improved spatiotemporal temperature control.
Mechanoelectrical properties of a GnF/PDMS composite controlled by the aspect ratio and concentration of GnF Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-24 Sungmin Park, Gyungmok Nam, Young Choi, Seungpyo Woo, Wonyoung Uhm, Sanghyun Park, Sang-Hee Yoon
A functional polymer-matrix composite (PMC) with controllable material properties is emerging as a promising material for the smart sensors in structural health monitoring (SHM). A GnF/PDMS composite is developed as a new functional PMC by blending graphite nanoflakes (GnFs) with polydimethylsiloxane (PDMS) where GnF and PDMS are used as a reinforcing/conductive filler and an elastic host matrix, respectively. We characterize the mechanoelectrical property-controllable GnF/PDMS composite, mainly focusing on the following issues: (i) determination of the best solvent for the preparation of a GnF/PDMS composite solution, (ii) exploration of changes in the mechanoelectrical properties of the functional PMC induced by variations in the aspect ratio (AR) and concentration of GnF. Among 9 kinds of common solvents, benzene shows both high GnF dispersibility and excellent PDMS compatibility, therefore being chosen as the optimal solvent. Variations in GnF AR (223–1017) and GnF concentration (1.0–25.0 wt.%) lead to significant changes in the elastic modulus, fracture strain, electrical conductivity, and gauge factor of the functional PMC in the ranges of 0.39–13.8 MPa, 0.09 to 2.54, 6.97 × 10−6 to 221.0 S/m, and 6 to about 37,000, respectively. The empirical models for predicting the mechanoelectrical properties of the functional PMC are also intensively studied. Our GnF/PDMS composite is expected to be used as a functional PMC for the development of smart sensors that detect deformation and fracture in structures.
Construction of chelation structure between Ca2+ and starch via reactive extrusion for improving the performances of thermoplastic starch Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-22 Shuidong Zhang, Zesheng Lin, Guo Jiang, Junsheng Wang, De-Yi Wang
A novel strategy was developed for the fabrication of thermoplastic starch with improved thermal and mechanical properties via chelating between starch and calcium gluconate (CG). Herein, the chelation structure between Ca2+ and hydrogen group in starch was constructed via reactive extrusion. CG (5–20 wt% based on starch) was added to the mixture (corn starch (CS) and glycerol (70:30 wt%)), then the mixtures were extruded by twin-screws extrusion to fabricate thermoplastic CS/CG (TPS-CG). FT-IR and XPS test were employed to confirm the chelation structure of CS/CG. TGA and TG-FTIR results demonstrated that chelation structure improved the thermal stability of CS/CGs, while reduced the amount of toxic volatile gas from the CS decomposition. The results of DMA, mechanical and rheological tests for TPS-CGs revealed that all the data increased when CG content ranged from 5% to 20%. The maximal increase in glass-transition temperature, notched impact and tensile strength, melt viscosity of TPS-CGs was 20 °C, 52.4%, 44.2% and 360%, respectively. The mechanism for these improvements and their variations by CGs content were attributed to improving the entanglement of starch molecular chain and the stiffness of TPS-CGs via the chelation structure. The study provided a convenient solution for TPS fabrication with satisfied properties.
Biodegradable silica rubber core-shell nanoparticles and their stereocomplex for efficient PLA toughening Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-21 Zibiao Li, Joseph K. Muiruri, Warintorn Thitsartarn, Xing Zhang, Beng Hoon Tan, Chaobin He
The dynamic mechanical properties of magnetorheological plastomers under high strain rate Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-21 Jiaqi Xu, Pengfei Wang, Haoming Pang, Yunpeng Wang, Jie Wu, Shouhu Xuan, Xinglong Gong
The dynamic mechanical properties of magnetorheological plastomers (MRPs) were investigated by using a Split Hopkinson Pressure Bar (SHPB) equipped with an electromagnetic accessory. Both the SHPB and rheological test indicated the mechanical properties of MRPs increased with strain rate, which demonstrated the typical rate dependent stiffening performance. With strain rate increased from 1580 s−1 to 7900 s−1, the maximum stress of MRPs increased from 31 MPa to 66 MPa. MRPs also exhibited a magnetic strengthening behavior due to the MR effect. Keeping the strain rate at 6500 s−1, the maximum stress increased 19.8 MPa as the magnetic flux density increased from 0 to 480 mT and the increase rate of maximum stress reached to 34%. Moreover, a high-speed camera was also used to capture the deformation of MRPs in both low and high strain rates. Based on the above results, a possible mechanism was proposed to investigate the dynamic mechanical properties of the MRPs. The synergistic effect between the magnetic field dependent particle structure evolution and polymer chain deformation were responded for the MR behavior and strain rate stiffening characteristic, respectively.
A predictive model of interfacial interactions between functionalised carbon fibre surfaces cross-linked with epoxy resin Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-21 Baris Demir, Kathleen M. Beggs, Bronwyn L. Fox, Linden Servinis, Luke C. Henderson, Tiffany R. Walsh
Attachment of amine-bearing molecules, denoted surface grafted molecules (SGMs), onto the surface of carbon fibre has been previously shown to enhance interfacial interactions at the carbon fibre/epoxy interface. However, the design principles inherent to optimising this enhancement are not yet established. Here, we investigate the influence of SGM design criteria on the interfacial mechanical response for three types of SGM via predictions based on molecular dynamics simulations, and by experimental measurements. The SGMs are covalently grafted to the graphitic fibre surface via in situ generated and decomposed phenyl diazo salts. All three SGMs possess a phenyl ring as the surface attachment point, and differ by the number and/or position (meta or para) of the amine-terminated side-chain(s) attached to the ring. The single-chain meta-substituted SGM produces the least interfacial enhancement, while the double-chain meta-substituted SGM enhances the interfacial shear strength by 29% relative to the control. In contrast, the single-chain para-SGM performs almost comparably to the double-chain meta-SGM. Our modelling predictions recover this trend and offer molecular-scale explanations for these findings, providing guidance in the design of effective surface-tailoring strategies to realise enhancements in the shear response of carbon fibre–epoxy interfaces.
A facile approach towards fabrication of lightweight biodegradable poly (butylene succinate)/carbon fiber composite foams with high electrical conductivity and strength Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-20 Tairong Kuang, Jiajun Ju, Zheyu Yang, Lihong Geng, Xiangfang Peng
Abstract Lightweight electrically conductive biodegradable polymer composites have been considered as a promising environmental-friendly alternative to replace the traditional petroleum-based CPCs because of the economic and ecological drawbacks of petroleum-based plastics. Herein, we demonstrated a facile and effective way to fabricate poly (butylene succinate) (PBS)/carbon fiber (CF) composites foams with lightweight, high-strength and improved conductive networks through the combination of solvent mixing, micro-injection molding and supercritical carbon dioxide (Sc CO2) foaming methods. Results showed that the resulting composite foams possessed much higher electrical conductivity (the percolation threshold decreased from 3.6 to 7.4 to 1.04–2.37 vol%), suggesting that the introduction of foaming technique could be beneficial for the formation of effective 3D conductivity networks. The composite foams presented a good compressive strength and a low density (reduced around ∼50%). Moreover, effects of different length and content of CF on the mechanical and thermal performance, rheological behavior, foaming properties and electrical conductivities of PBS/CF composites have been investigated.
Transparent and flexible high frequency transmission lines based on composite structure comprising silver nanowires and polyvinyl butyral Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-19 Sang-Woo Kim, Kwangho Kim, Wansoo Nah, Cheul-Ro Lee, Seung-Boo Jung, Jong-Woong Kim
Percolated networks of silver nanowires (AgNWs) have attracted intensive attention because of their remarkable mechanical stability, along with their excellent optical and electrical performance for the fabrication of flexible transparent electrodes. Most prior research has mainly focused on fabricating transparent electrodes that can be used in optoelectronic devices such as touch sensors, light emitting diodes, and photovoltaics. However, fabrication of transparent and flexible transmission lines designed to conduct alternating current of high frequency has not been reported so far. Herein, we developed highly transparent, mechanically stable transmission line by employing inverted layer processing (ILP) in order to embed the AgNWs just below the surface of a free-standing transparent polymer. For this, we synthesized polyvinyl butyral (PVB), which can be prepared from polyvinyl alcohol by reaction with butyraldehyde, for AgNW support. AgNWs deposited on a preliminary substrate (glass) were plasmonically sintered to significantly enhance their conductivity, and then transferred to the surface of the cured PVB film by the ILP. Measurements and simulation of specially designed coplanar waveguide circuits comprising AgNWs and PVB revealed that the fabricated electrode can simultaneously provide impressive transmission performance as well as excellent mechanical flexibility and transparency. An interesting finding was that the transmission characteristics and mechanical stability are in a trade-off relationship, which needs to be carefully considered in the design and selection of materials for the flexible transmission lines.
3D printing two-dimensional periodic structures to tailor in-plane dynamic responses and fracture behaviors Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-19 Ming Lei, Craig M. Hamel, Chao Yuan, Haibao Lu, H. Jerry Qi
High-performance biological structural materials such as bone and spider silk have evolved soft and stiff components to optimize the load transfer path. This inspired many researches to achieve engineering composites with significantly improved properties. In this paper, we designed a class of 2D elastomer filled composites with periodic units. The designs of these composites were realized by 3D printing of a soft elastomer and a stiff plastic. The plastic constructed a honeycomb-like mesh, in which the soft elastomer formed isolated inclusions. Variation of the mesh geometries, the elastomer content, and the constituent material properties could tune the in-plane dynamic responses and fracture behaviors. Dynamic mechanical analysis measurements showed two tanδ peaks, corresponding to the elastomer and the plastic. By changing the geometry, a very wide range of storage modulus values (about three orders of magnitudes) could be achieved at room temperature. The fracture strain of the composites was found to increase with the elastomer content, and an obvious brittle-ductile transition was observed. Tough samples showed several stress plateaus and a trumpet-shaped crack profile. Increasing the vertex angles of the rhombus filler geometry was found to result in a brittle-ductile transition. In both experiments and simulations, a forward-backward crack propagation mode was observed, indicating that soft elastomer inclusions stabilize the crack propagation. Compared to staggered composites with stiff inclusions, the current design with soft inclusions showed higher modulus, tensile strength and toughness.
Elastomer nanocomposites with superior dynamic mechanical properties via Trans-1, 4-poly (butadiene-co-isoprene) incorporation Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-17 Xinping Zhang, Honghong Cui, Liyuan Song, Huicheng Ren, Riguo Wang, Aihua He
Effect of tackification on in-plane shear behaviours of biaxial woven fabrics in bias extension test: Experiments and finite element modeling Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-16 Xiaoran Zhao, Gang Liu, Ming Gong, Jiupeng Song, Yan Zhao, Shanyi Du
As one of the most reliable tests for fabric in-plane deformation characterization, bias extension test is widely accepted as following the Pin-Joint-Net assumption. Hence, researchers always take in-plane shear behaviour of tackified woven fabrics following that assumption for granted. However, it is lack of evidence. In this paper, based on the distinctive load fluctuation observed during bias extension and picture frame tests of CF3031 biaxial woven fabrics with varying tackifier content, we established a new model called “Gradual Deformation Model” as deformation assumption to describe the different bias extension behaviours of tackified woven fabrics instead of Pin-Joint-Net assumption. The model validation was implemented sufficiently via digital image correlation technology and finite element analysis. Due to the good correlation between experimental and numerical results, it is reasonable to claim that the main effect of tackification on in-plane shear behaviours is the formation of great resistance to inter-tow shear, inter-tow sliding and cross-over point sliding.
Numerical study of the effects of irregular pores on transverse mechanical properties of unidirectional composites Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-16 Lehua Qi, Xujiang Chao, Wenlong Tian, Wenjing Ma, Hejun Li
For investigating the effect of the irregular pores on transverse elastic properties of the unidirectional Carbon/Carbon (C/C) composites, a new strategy is proposed to generate the representative volume element (RVE) on the basis of scanning electron microscope (SEM) images, in which these pores are approximated as the polygons and the identical fibers are generated by using the RSA algorithm. A good agreement is achieved by comparing the effective elastic properties obtained from the FEM-homogenization techniques to those predicted by experimental tests and two-step Mori-Tanaka method. FEM results indicate that the convergence of the results is seen when the number of vertices of the polygon reaches 40 and the RVE edge length is eight times of the maximum pores size (L/lmax = 8). Meanwhile, the average departure from isotropy is below 5% and the UD composites can be considered as transverse isotropic. The effective transverse elastic properties would decrease with increase of the porosity and with increase of the pores clustering ηp.
Mechanical behavior of carbon nanotube yarns with stochastic microstructure obtained by stretching buckypaper Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-16 A. Sengab, R.C. Picu
The development of yarns composed primarily from carbon nanotubes (CNTs) has been pursued recently with the intent of transferring to the yarn the exceptional mechanical and transport properties of individual nanotubes. In this work we study the process of yarn formation by dry stretching buckypaper, and the mechanical behavior of the resulting yarns, function of the CNT length and of the state of the CNT assembly before stretching. The analysis is performed using a coarse grained, bead-spring representation for individual CNTs. It begins with a random buckypaper structure composed from CNTs of diameter 13.5 Å. This structure is stretched to form a yarn. This occurs once the stretch ratio becomes larger than a threshold which depends on the CNT length. At the threshold, adhesion stabilizes a highly aligned packing of CNT bundles. Packing defects and pores, reminiscent of the initial structure of the buckypaper, are incorporated in the yarn. The yarn is further tested in uniaxial tension. The defects have little effect on the mechanical behavior of the resulting yarns. However, the behavior depends sensitively on the degree of packing of the CNTs in the sub-bundles forming the yarn. Therefore, the initial structure of the buckypaper has little effect on the performance of the yarn. Increasing the CNT length increases the yarn flow stress and this is associated with the residual tortuosity of the CNTs in the yarn. Decreasing the temperature or increasing the strain rate lead to a small increase of the flow stress. These results have implications for yarn design, which are discussed in the article.
High electromechanical performance of modified electrostrictive polyurethane three-phase composites Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-15 Ardimas, Chatchai Putson, Nantakan Muensit
In order to enhance the electrostrictive polymer, the polyurethane has been modified with conductive fillers that are promising for actuator applications, energy conversion, and sensors. The polyurethane (PU) matrix and the conductive fillers such as graphene nanosheets (GRN) and polyaniline nanopowder (PANI) were prepared to gain films by solution casting method. The morphology, structure and thermal behavior of PU three-phase composite were observed by SEM imaging, FTIR, and DSC techniques. In addition, the electrical and mechanical properties of polyurethane filled with both composites were investigated by an LCR meter and strain gauge setup. In order to study the electrostriction behavior, the electric field induced strain of PU three-phase composite films was monitored via lock-in amplifier at a low frequency of 1 Hz. A greater electrostriction effect of the PU three-phase composites at low electric field significantly related with contribute to conduction and interfacial polarization base on space charges distribution, filler-filler network and microstructure on crystallinity in the HS domain of PU matrix. Therefore, electrostriction behavior in the PU three-phase composites has been discussion. It was known that why the three-phase composites can provide high electromechanical performance for actuator applications.
How can we make carbon nanotube yarn stronger? Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-15 Yeonsu Jung, Young Shik Cho, Jae Won Lee, Jun Young Oh, Chong Rae Park
There has been remarkable progress with regard to the fabrication of yarns based on high-performance carbon nanotubes (CNTs). However, the theoretically predicted tensile strength of CNTs has yet to be realized in practical CNT yarns or CNT-reinforced composites. Having considered that there are few systematic guidelines for preparing high-strength CNT yarns, we attempted to revisit the-state-of-the-art progress in the theories and yarn formation processes of CNT yarns and then draw possible correlations between the intrinsic and extrinsic structural parameters of elementary CNTs, yarn formation processes and the tensile strength of the resulting CNT yarns. On the basis of these considerations and discussions of advanced technologies and theoretical approaches, possible routes to improve the strength of CNT yarns further are suggested.
Investigation of strain history in fast and conventional curing epoxy matrix composites by FBGs Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-14 Yixin Qi, Dazhi Jiang, Su Ju, Jianwei Zhang
A comprehensive understanding of strain history in resin matrix composite, which is caused by variability of thermo-mechanical properties of the resin during composite processing, is essential to allow better design and control of properties of the resin matrix composite. In this paper, to know strain history of fast curing epoxy matrix composite and differences of strain history between fast and conventional curing epoxy matrix composites well, temperature and strain history at different locations in ten-ply unidirectional carbon-fiber fabrics reinforced the fast and conventional curing epoxy matrix composite laminates manufactured by wet lay-up method were measured by fiber Bragg grating (FBG) sensors. Results shown that the peak temperature due to curing exothermal reaction was 133.7 °C in both the 1st ply and the 5th ply in the fast curing composite when cure temperature profile settled at 80 °C, which was 27.4 °C higher than that in the conventional curing composite. Cure residual strain in the 1st ply and the 5th ply in the fast curing composite were −5183.3 με and −4074.7 με, respectively; while they were −2975.9 με and −2660.8 με in the conventional curing composite. The related properties of rheology and cure kinetics of the epoxy resin were thus given in advance.
Helical flow-driven alignment of off-axial silver-functionalized titanium dioxide fibers in polypropylene tube suitable for medical applications Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-14 Kailin Zhang, Xiao Li, Min Nie, Qi Wang
Inspired by Bouligand-type structure in natural materials featured with helically-aligned reinforcing fibers and superior kink-resistance, we demonstrated an analogous architectural configuration in polypropylene (PP) tube by mean of manipulating helical flow and Ag-coated titanium dioxide (TiO2) fibers. Firstly, the dopamine-assisted immobilization and in situ reduction of Ag ions were completed on the surface of TiO2 fiber, endowing the latter with antibacterial property. Then, the functionalized fibers were introduced into PP matrix, and extruded longitudinally, simultaneously with mandrel rotation, constructing a unique helical flow. Preferred orientation driven by the applied flow assembled the bioinspired Bouligand-like structure with helically-aligned functionalized TiO2 fibers, benefiting torque load bearing and thereby the bulk kink-resistance of polymer tube accompanied by high antibacterial activity. This was exemplified by a substantial increase of 40% in hoop strength with large bacterial inhibition zone in comparison with the pure PP counterpart prepared via convention extrusion. This Bouligand-mimetic alignment strategy can open up a promising possibility of engineering and develop a series of reinforced architectures via simple industrial melt process, satisfying special functionalities and applications unavailable with the other processing technologies.
Simulating the effects of carbon nanotube continuity and interfacial bonding on composite strength and stiffness Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-14 Benjamin D. Jensen, Gregory M. Odegard, Jae-Woo Kim, Godfrey Sauti, Emilie J. Siochi, Kristopher E. Wise
Molecular dynamics simulations of carbon nanotube (CNT) composites, in which the CNTs are continuous across the periodic boundary, overestimate the experimentally measured mechanical properties of CNT composites along the fiber direction. Since the CNTs in these composites are much shorter than the composite dimensions, load must be transferred either directly between CNTs or through the matrix, a mechanism that is absent in simulations of effectively continuous CNTs. In this study, the elastic and fracture properties of high volume fraction discontinuous carbon nanotube/amorphous carbon composite systems were compared to those of otherwise equivalent continuous CNT composites using ReaxFF reactive molecular dynamics simulations. The simulation results quantify the dependence of composite mechanical properties on the number of nanotube-matrix interfacial covalent bonds. Furthermore, the mechanical impact of interfacial bonding was decomposed to reveal its effect on the properties of the CNTs, the interfacial layer of matrix, and the bulk matrix. For the composites with continuous reinforcement, it was found that any degree of interfacial bonding has a negative impact on axial tensile strength and stiffness. This is due to disruption of the structure of the CNTs and interfacial matrix layer by the interfacial bonds. For the discontinuous composites, the modulus was maximized between 4% and 7% interfacial bonding and the strength continued to increase up to the highest levels of interfacial bonding studied. Areas of low stress and voids were observed in the simulated discontinuous composites at the ends of the tubes, from which fracture was observed to initiate. Experimental carbon nanotube yarn composites were fabricated and tested. The experimental results illustrate the knockdown factors that reduce composite mechanical properties relative to those of the tubes themselves.
Enhanced dielectric tunability and energy storage properties of plate-like Ba0.6Sr0.4TiO3/poly(vinylidene fluoride) composites through texture arrangement Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-13 Li Wang, Feng Gao, Jie Xu, Kena Zhang, Jie Kong, Mike Reece, Haixue Yan
Plate-like (Ba0.6Sr0.4)TiO3 (P-BST) particles were synthesized via topochemical microcrystal conversion using a two-step molten salt method. In addition, P-BST/poly(vinylidene fluoride) (PVDF) textured composites were fabricated using a tape casting and hot pressing method. The influence of the P-BST particle size on the microstructure, dielectric tunability, and energy storage properties of the P-BST/PVDF textured composites was investigated. The results revealed that P-BST/PVDF textured composites can be obtained with preferred orientation of plate-like particles, which exhibit uniform directionality in the PVDF matrix. The dielectric properties of these composites increased with increasing P-BST particle size. A new criterion EP80 was proposed for evaluating the dielectric tunability of composites. The optimal properties of the P-BST/PVDF textured composite (minimum threshold electric field: 14 kV/mm, minimum EP80: 29 kV/mm, and maximum energy storage density: 6.36 J/cm3) were realized at a P-BST particle size of 11.47 μm. A dielectric tunability model for inorganic/organic composites with respect to the shape factor (n) of the inorganic fillers was proposed and used to simulate the dielectric tunability of the textured composites. For the P-BST/PVDF composite, n of 4–5 in the model corresponded to P-BST particle sizes of 5.19 μm–11.47 μm.
Strain sensing behaviors of GnPs/epoxy sensor and health monitoring for composite materials under monotonic tensile and cyclic deformation Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-13 Shaowei Lu, Caijiao Tian, Xiaoqiang Wang, Lu Zhang, Kai Du, Keming Ma, Tao Xu
The graphene platelets (GnPs)/epoxy flexible sensor with controllable sensitivity and linearity can be used to monitor the deformation and damage of composite structures. The sensitivity and linearity can be regulated by dispersing different content of GnPs in epoxy and the dispersion was better improved by optimizing ultrasonic time and the ball mill mixing process. The GnPs/epoxy mixture exhibited relatively low percolation threshold of 0.76 vol %. In this paper, GnPs/epoxy mixtures with GnPs loading of 0.84 vol.%, 1.05 vol % and 1.58 vol % were selected as damage detecting and strain sensor, and the characteristics of sensors were demonstrated via various mechanical tests. The monotonic tensile results suggest that there are three different linear change sensing stages, (1–0.2%), (0.2%–0.6%) and (0.6%–1.2%), the linear growth of the electrical response is softened while the linear tendency is enhanced due to increasing GnPs content, and it exhibits relatively high gauge factor of 11.81, 15.25 and 22.54 for 0.84 vol %, 3.63, 8.13, 11.46 for 1.05 vol % and 2.53, 3.77, 4.69 for 1.58 vol % in different sensing stages respectively. The sensor of 0.84 vol % is more reversibility than 1.05 vol % upon cyclic loading-unloading test. The GnPs/epoxy sensor show promising applications for the damage monitoring of structural composite in the field of aerospace.
Multi-functional hydroxyapatite/polyvinyl alcohol composite aerogels with self-cleaning, superior fire resistance and low thermal conductivity Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-13 Wenwen Guo, Jiajia Liu, Ping Zhang, Lei Song, Xin Wang, Yuan Hu
Hybrid inorganic/polymer composite aerogels combine the advantages of both components which can overcome the brittle fracture of inorganic aerogels as well as high flammability of polymeric aerogels. Herein, we reported a facile approach to prepare polyvinyl alcohol (PVA)-hydroxyapatite (HAP) composite aerogel by freeze-casting process towards multi-functional aerogel materials. The incorporation of HAPs led to significant reduction in the peak heat release rate (-79%), total heat release (-76%), specific extinction area (-65%) and CO production (-45%). Vertical burning tests also manifested that PVA-HAP composite aerogels displayed excellent fire resistance and self-extinguishing behaviours. The resultant PVA-HAP composite aerogels also showed a low thermal conductivity (33.6–38.7 mW m−1 K−1). The hydrogen bonding formed between the HAP and the PVA matrix endowed the resultant composite aerogels with a specific modulus (58.7 kN m−1 kg−1) which was comparable to or even higher than those reported by state-of-the-art foams, including polystyrene foams, polyurethane foams and silica aerogels. After a facile polydimethylsiloxane treatment, the resultant PVA-HAP composite aerogels also exhibited water-repellent and self-cleaning capacity, which is a promising candidate as building insulating materials.
Ultralow electrical percolation in melt-compounded polymer composites based on chemically expanded graphite Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-10 Peng Wang, Haodan Chong, Jiajia Zhang, Yanhao Yang, Hongbin Lu
It has been difficult to construct electrical percolation networks in melt-compounded polymer composites due to shear-induced network destruction, especially for low graphene content composites. To overcome this issue, here we employ chemically expanded graphite (CEG) to construct conductive networks in which the polymer molecules would penetrate into the inner part of CEG to form a polymer entrapped in CEG structure. This novel polymer entrapped in CEG structure is very useful for the effective charge transfer and further construction of conductive networks in the process of melt compounding. The final polymer composites exhibit an ultralow electrical conductive percolation threshold of 0.29 vol% after melt compounding which is almost among the lowest level compared with those of other melt-compounded polymer composites. Besides, the thermal conductivity of the composites is also significantly enhanced. This strategy here has provided a new way to maintain the conductive networks and decrease the electrical percolation threshold in the melt-compounded polymer composites through constructing polymer entrapped in conductive fillers structure.
Mechanical enhancement effect of the interlayer hybrid CNT film/carbon fiber/epoxy composite Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-10 Tianshu Li, Min Li, Yizhuo Gu, Shaokai Wang, Qingwen Li, Zuoguang Zhang
Floating catalyst chemical vapor deposition carbon nanotube (CNT) film was intercalated into carbon fiber (CF) prepregs to fabricate hybrid composites. The effect of CNT film thickness was studied by using a 25 μm thick film and an ultrathin 2 μm film respectively. The results showed that the ultrathin CNT film interlayer had dramatically improved the compression strength of hybrid composite by 34% compared with CF/epoxy control composite owing to the altered failure modes. The damping ratio of ultrathin CNT film hybridized composite was substantially increased by two orders of magnitude, due to the energy dissipation of numerous nanoscale interconnections and interfaces. Moreover, the interlaminar properties and water resistance of the hybrid composites were all improved. Since a small amount of CNT film can significantly enhance the mechanical properties of CF/epoxy composite, this type of hybrid composite has potential application in multifunctional lightweight structures.
Recyclable and superelastic aerogels based on carbon nanotubes and carboxymethyl cellulose Compos. Sci. Technol. (IF 4.873) Pub Date : 2018-02-10 Alireza Hajian, Qiliang Fu, Lars A. Berglund
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
- Acc. Chem. Res.
- ACS Appl. Mater. Interfaces
- ACS Biomater. Sci. Eng.
- ACS Catal.
- ACS Cent. Sci.
- ACS Chem. Biol.
- ACS Chem. Neurosci.
- ACS Comb. Sci.
- ACS Earth Space Chem.
- ACS Energy Lett.
- ACS Infect. Dis.
- ACS Macro Lett.
- ACS Med. Chem. Lett.
- ACS Nano
- ACS Omega
- ACS Photonics
- ACS Sens.
- ACS Sustainable Chem. Eng.
- ACS Synth. Biol.
- Acta Biomater.
- Acta Crystallogr. A Found. Adv.
- Acta Mater.
- Adv. Colloid Interface Sci.
- Adv. Electron. Mater.
- Adv. Energy Mater.
- Adv. Funct. Mater.
- Adv. Healthcare Mater.
- Adv. Mater.
- Adv. Mater. Interfaces
- Adv. Opt. Mater.
- Adv. Sci.
- Adv. Synth. Catal.
- AlChE J.
- Anal. Bioanal. Chem.
- Anal. Chem.
- Anal. Chim. Acta
- Anal. Methods
- Angew. Chem. Int. Ed.
- Annu. Rev. Anal. Chem.
- Annu. Rev. Biochem.
- Annu. Rev. Environ. Resour.
- Annu. Rev. Food Sci. Technol.
- Annu. Rev. Mater. Res.
- Annu. Rev. Phys. Chem.
- Appl. Catal. A Gen.
- Appl. Catal. B Environ.
- Appl. Clay. Sci.
- Appl. Energy
- Aquat. Toxicol.
- Arab. J. Chem.
- Asian J. Org. Chem.
- Atmos. Environ.
- Carbohydr. Polym.
- Catal. Commun.
- Catal. Rev. Sci. Eng.
- Catal. Sci. Technol.
- Catal. Today
- Cell Chem. Bio.
- Cem. Concr. Res.
- Ceram. Int.
- Chem. Asian J.
- Chem. Bio. Drug Des.
- Chem. Biol. Interact.
- Chem. Commun.
- Chem. Educ. Res. Pract.
- Chem. Eng. J.
- Chem. Eng. Sci.
- Chem. Eur. J.
- Chem. Mater.
- Chem. Phys.
- Chem. Phys. Lett.
- Chem. Phys. Lipids
- Chem. Rev.
- Chem. Sci.
- Chem. Soc. Rev.
- Chin. J. Chem.
- Combust. Flame
- Compos. Part A Appl. Sci. Manuf.
- Compos. Sci. Technol.
- Compr. Rev. Food Sci. Food Saf.
- Comput. Chem. Eng.
- Constr. Build. Mater.
- Coordin. Chem. Rev.
- Corros. Sci.
- Crit. Rev. Food Sci. Nutr.
- Crit. Rev. Solid State Mater. Sci.
- Cryst. Growth Des.
- Curr. Opin. Chem. Eng.
- Curr. Opin. Colloid Interface Sci.
- Curr. Opin. Environ. Sustain
- Curr. Opin. Solid State Mater. Sci.
- Ecotox. Environ. Safe.
- Electrochem. Commun.
- Electrochim. Acta
- Energy Environ. Sci.
- Energy Fuels
- Energy Storage Mater.
- Environ. Impact Assess. Rev.
- Environ. Int.
- Environ. Model. Softw.
- Environ. Pollut.
- Environ. Res.
- Environ. Sci. Policy
- Environ. Sci. Technol.
- Environ. Sci. Technol. Lett.
- Environ. Sci.: Nano
- Environ. Sci.: Processes Impacts
- Environ. Sci.: Water Res. Technol.
- Eur. J. Inorg. Chem.
- Eur. J. Med. Chem.
- Eur. J. Org. Chem.
- Eur. Polym. J.
- J. Acad. Nutr. Diet.
- J. Agric. Food Chem.
- J. Alloys Compd.
- J. Am. Ceram. Soc.
- J. Am. Chem. Soc.
- J. Am. Soc. Mass Spectrom.
- J. Anal. Appl. Pyrol.
- J. Anal. At. Spectrom.
- J. Antibiot.
- J. Catal.
- J. Chem. Educ.
- J. Chem. Eng. Data
- J. Chem. Inf. Model.
- J. Chem. Phys.
- J. Chem. Theory Comput.
- J. Chromatogr. A
- J. Chromatogr. B
- J. Clean. Prod.
- J. CO2 UTIL.
- J. Colloid Interface Sci.
- J. Comput. Chem.
- J. Cryst. Growth
- J. Dairy Sci.
- J. Electroanal. Chem.
- J. Electrochem. Soc.
- J. Environ. Manage.
- J. Eur. Ceram. Soc.
- J. Fluorine Chem.
- J. Food Drug Anal.
- J. Food Eng.
- J. Food Sci.
- J. Funct. Foods
- J. Hazard. Mater.
- J. Heterocycl. Chem.
- J. Hydrol.
- J. Ind. Eng. Chem.
- J. Inorg. Biochem.
- J. Magn. Magn. Mater.
- J. Mater. Chem. A
- J. Mater. Chem. B
- J. Mater. Chem. C
- J. Mater. Process. Tech.
- J. Mech. Behav. Biomed. Mater.
- J. Med. Chem.
- J. Membr. Sci.
- J. Mol. Catal. A Chem.
- J. Mol. Liq.
- J. Nat. Gas Sci. Eng.
- J. Nat. Prod.
- J. Nucl. Mater.
- J. Org. Chem.
- J. Photochem. Photobiol. C Photochem. Rev.
- J. Phys. Chem. A
- J. Phys. Chem. B
- J. Phys. Chem. C
- J. Phys. Chem. Lett.
- J. Polym. Sci. A Polym. Chem.
- J. Porphyr. Phthalocyanines
- J. Power Sources
- J. Solid State Chem.
- J. Taiwan Inst. Chem. E.
- Macromol. Rapid Commun.
- Mass Spectrom. Rev.
- Mater. Chem. Front.
- Mater. Des.
- Mater. Horiz.
- Mater. Lett.
- Mater. Sci. Eng. A
- Mater. Sci. Eng. R Rep.
- Mater. Today
- Meat Sci.
- Med. Chem. Commun.
- Microchem. J.
- Microchim. Acta
- Micropor. Mesopor. Mater.
- Mol. Biosyst.
- Mol. Cancer Ther.
- Mol. Catal.
- Mol. Nutr. Food Res.
- Mol. Pharmaceutics
- Mol. Syst. Des. Eng.
- Nano Energy
- Nano Lett.
- Nano Res.
- Nano Today
- Nano-Micro Lett.
- Nanomed. Nanotech. Biol. Med.
- Nanoscale Horiz.
- Nat. Catal.
- Nat. Chem.
- Nat. Chem. Biol.
- Nat. Commun.
- Nat. Energy
- Nat. Mater.
- Nat. Med.
- Nat. Methods
- Nat. Nanotech.
- Nat. Photon.
- Nat. Prod. Rep.
- Nat. Protoc.
- Nat. Rev. Chem.
- Nat. Rev. Drug. Disc.
- Nat. Rev. Mater.
- Natl. Sci. Rev.
- Neurochem. Int.
- New J. Chem.
- NPG Asia Mater.
- npj 2D Mater. Appl.
- npj Comput. Mater.
- npj Flex. Electron.
- npj Mater. Degrad.
- npj Sci. Food
- Pharmacol. Rev.
- Pharmacol. Therapeut.
- Photochem. Photobiol. Sci.
- Phys. Chem. Chem. Phys.
- Phys. Life Rev.
- PLOS ONE
- Polym. Chem.
- Polym. Degrad. Stabil.
- Polym. J.
- Polym. Rev.
- Powder Technol.
- Proc. Combust. Inst.
- Prog. Cryst. Growth Ch. Mater.
- Prog. Energy Combust. Sci.
- Prog. Mater. Sci.
- Prog. Photovoltaics
- Prog. Polym. Sci.
- Prog. Solid State Chem.
- Sci. Adv.
- Sci. Bull.
- Sci. Rep.
- Sci. Total Environ.
- Sci. Transl. Med.
- Scr. Mater.
- Sens Actuators B Chem.
- Sep. Purif. Technol.
- Small Methods
- Soft Matter
- Sol. Energy
- Sol. Energy Mater. Sol. Cells
- Solar PRL
- Spectrochim. Acta. A Mol. Biomol. Spectrosc.
- Surf. Sci. Rep.
- Sustainable Energy Fuels