聚合物复合材料摩擦学研究进展

综述了聚合物复合材料的摩擦学研究概况，分析了不同填充材料及其含量、纤维填充材料方向及环境等因素对聚合物复合材料摩擦学性能的影响，指出不同填充材料对提高基体耐磨性的影响不同，且其提高基体耐磨性的机理也不同。     

Multiwalled carbon nanotube reinforced polymer composites

Due to their high stiffness and strength, as well as their electrical conductivity, carbon nanotubes are under intense investigation as fillers in polymer matrix composites. The nature of the carbon nanotube/polymer bonding and the curvature of the carbon nanotubes within the polymer have arisen as particular factors in the efficacy of the carbon nanotubes to actually provide any enhanced stiffness or strength to the composite. Here the effects of carbon nanotube curvature and interface interaction with the matrix on the composite stiffness are investigated using micromechanical analysis. In particular, the effects of poor bonding and thus poor shear lag load transfer to the carbon nanotubes are studied. In the case of poor bonding, carbon nanotubes waviness is shown to enhance the composite stiffness.     

陶瓷晶须/聚合物基复合材料的研究进展

概述了钛酸钾、氧化锌、硼酸铝等陶瓷晶须增强聚合物基复合材料的研究进展,探讨了晶须含量、晶须表面处理、材料前处理方法等对提高复合材料力学性能及摩擦学性能的影响,明确了适当的表面改性方法可以使晶须的增强效果更为明显,指出了在晶须/聚合物结合面微观形态观察和分析方面的不足,提出了构建晶须/聚合物复合材料的理论模型、预测复合材料性能的研究方向.     

Interface characteristics of nanorope reinforced polymer composites

A shear-lag model is proposed to obtain interface characteristics of nanorope reinforced polymer composites using representative volume element (RVE) concept. In the axisymmetric RVE, the nanorope is modelled as a closed-packed cylindrical lattice consisting seven single-walled carbon nanotubes. In the model, rope is considered to be perfectly bonded with the polymer resin where the nanotubes are assumed to be chemically non-bonded with each other in the rope system. Since, nanotubes are considered to be non-bonded in the nanorope there must exist a van der Waals interaction in terms of Lennard-Jones potential. A separate model is also proposed to determine the cohesive stress caused by this interaction. Closed form analytical solutions are derived for stress components of rope, resin and individual carbon nanotubes in the rope system. Parametric study has also been conducted to investigate the influences of key composite factors involved at both perfectly bonded and non-bonded interfaces.     

Strength prediction of multi-layer plain weave textile composites using the direct micromechanics method

Previously developed micromechanical methods for stiffness and strength prediction are adapted for analysis of multi-layer plain weave textile composites. Utilizing the direct micromechanics method (DMM) via finite element modeling, three methods are presented: (a) direct simulation of a multi-layer plain weave textile composite; (b) micromechanical analysis of a single layer of interest from the force and moment resultants acting on that layer; and (c) application of the previously developed quadratic stress-gradient failure theory to the layer of interest. In comparison to direct modeling, the other two techniques show only 5% difference over a number of random test cases. Several practical design examples of strength prediction are included to illustrate the importance and accuracy of method implementation.     

聚合物基天然植物纤维增强复合材料研究进展

综述了近几年来国内外在聚合物基天然植物纤维增强复合材料领域的最新研究进展,介绍了聚合物基天然植物纤维增强复合材料的增强纤维种类、树脂基体种类以及其他因素对复合材料性能的影响,并展望了这类复合材料的发展及应用前景。     

高聚物增强木质基复合材料的结构与性能

为探索性能优异的高聚物增强木质基复合材料的制备方法, 以大青杨木材为研究对象, 选用双功能性单体甲基丙烯酸缩水甘油酯(GMA)和丙烯酸类单体甲基丙烯酸甲酯(MMA), 通过加热引发聚合的方式制得P(GMAcoMMA)/木材复合材料。利用SEM、 FTIR和XRD表征其结构, 并测试其相关性能。结果表明: GMA的加入, 使高聚物与木材细胞壁紧密接触, 界面相互作用力增强; GMA一端的环氧基团, 与木材细胞壁上的羟基充分发生了化学反应, 其双键与MMA单体发生自由基共聚合反应, 从而使P(GMAcoMMA)接枝在木材细胞壁上, 并且主要以无定形态存在。与未改性的木材相比, P(GMAcoMMA)/木材复合材料的静曲强度(MOR)、 尺寸稳定性、 防腐性能和热稳定性依次提高90.53%、 54.05%、 92.85%和31℃。      

Optical coherence tomography of glass reinforced polymer composites

Optical coherence tomography (OCT) is a nondestructive and noncontact technique to image microstructure within scattering media. The application of OCT to highly scattering materials such as polymer composites is especially challenging. In this work, OCT is evaluated as a technique to image fiber tows and voids in two materials: an epoxy E-glass-reinforced composite and a vinyl-ester E-glass-reinforced composite. Features detected using OCT are compared with optical microscopy. Fiber architecture and voids of glass-reinforced polymer composites can be successfully imaged using OCT. The quality of the OCT image is strongly affected by the refractive index mismatch between the fibers and reinforcement. The largest sources of noise in the images arise from fiber lens effects, interference from within the sample, and a very large reflection at the surface.     

Mechanical properties of natural fibre reinforced polymer composites

During the last few years, natural fibres have received much more attention than ever before from the research community all over the world. These natural fibres offer a number of advantages over traditional synthetic fibres. In the present communication, a study on the synthesis and mechanical properties of new series of green composites involving Hibiscus sabdariffa fibre as a reinforcing material in urea-formaldehyde (UF) resin based polymer matrix has been reported. Static mechanical properties of randomly oriented intimately mixed Hibiscus sabdariffa fibre reinforced polymer composites such as tensile, compressive and wear properties were investigated as a function of fibre loading. Initially urea-formaldehyde resin prepared was subjected to evaluation of its optimum mechanical properties. Then reinforcing of the resin with Hibiscus sabdariffa fibre was accomplished in three different forms: particle size, short fibre and long fibre by employing optimized resin. Present work reveals that mechanical properties such as tensile strength, compressive strength and wear resistance etc of the urea-formaldehyde resin increases to considerable extent when reinforced with the fibre. Thermal (TGA/DTA/DTG) and morphological studies (SEM) of the resin and biocomposites have also been carried out.     

Multiscale modeling of carbon nanotube reinforced polymer composites

This article examines the effect of interfacial load transfer on the stress distribution in carbon nanotube/polymer composites through a stress analysis of the nanotube/matrix system. Both isostrain and isostress loading conditions are investigated. The nanotube is modeled by the molecular structural mechanics method at the atomistic level. The matrix is modeled by the finite element method, and the nanotube/matrix interface is assumed to be bonded either perfectly or by van der Waals interactions. The fundamental issues examined include the interfacial shear stress distribution, stress concentration in the matrix in the vicinity of nanotube ends, axial stress profile in the nanotube, and the effect of nanotube aspect ratio on load transfer.     

纤维增强聚合物基复合材料的低温性能

对纤维增强聚合物基复合材料在低温领域的实际应用进行了分类介绍,通过对纤维增强聚合物基复合材料的低温性能、性能影响因素和作用机理、低温应用安全性等方面的研究工作进行总结,突出各类纤维增强聚合物基复合材料低温下的性能优势,阐明了材料性能的不足之处及相应改进措施.对于实际低温应用中纤维增强聚合物基复合材料的选择、性能设计优化,系统安全性的增强提供了参考作用.     

Viscoelasticity in carbon nanotube composites

Polymer composites reinforced by carbon nanotubes have been extensively researched for their strength and stiffness properties. Unless the interface is carefully engineered, poor load transfer between nanotubes (in bundles) and between nanotubes and surrounding polymer chains may result in interfacial slippage and reduced performance. Interfacial shear, although detrimental to high stiffness and strength, could result in very high mechanical damping, which is an important attribute in many commercial applications. We previously reported evidence of damping in nanocomposites by measuring the modal response (at resonance) of cantilevered beams with embedded nanocomposite films. Here we carry out direct shear testing of epoxy thin films containing dense packing of multiwalled carbon nanotube fillers and report strong viscoelastic behaviour with up to 1,400% increase in loss factor (damping ratio) of the baseline epoxy. The great improvement in damping was achieved without sacrificing the mechanical strength and stiffness of the polymer, and with minimal weight penalty. Based on the interfacial shear stress (approximately 0.5 MPa) at which the loss modulus increases sharply for our system, we conclude that the damping is related to frictional energy dissipation during interfacial sliding at the large, spatially distributed, nanotube-nanotube interfaces.     

改性透辉石增强聚乙烯复合材料的研究

采用硬脂酸和铝酸酯两种改性剂对超细透辉石粉体进行表面改性,通过接触角和活化指数评价表面改性效果,同时利用熔融共混塑化成型法制备透辉石/聚乙烯复合材料,探讨了不同偶联剂对复合材料力学性能的影响。用SEM观察了其在聚乙烯基体中的分散情况,用X射线衍射仪对复合材料的结晶状况进行了表征。结果表明,经过适当表面处理的透辉石可以通过共混均匀分散在聚乙烯中,粒子与基体界面结合良好,复合材料的力学性能得到一定的提高,从而降低生产成本。     

Stochastic matrix-cracking model for textile reinforced cementitious composites under tensile loading

When cementitious composites are loaded in tension, cracks initiate and propagate at very low stress levels, leading to a non-linear constitutive behaviour. A first attempt to model this behaviour (the well-known ACK-model) was done by Aveston et al. [1] and Aveston and Kelly [2]. However, according to several authors [3–10], the main limitation of this model is the stochastic nature of the strength of the cementitious matrix, which is not included in the ACK-model. Based on the work of Curtin et al. [7, 10], presenting a statistical treatment of matrix crack evolution in unidirectionally reinforced ceramic micro-composites with single fibres; a two-parameter Weibull model is proposed in this paper to describe the matrix strength. It was shown by Curtin et al. [7, 10] that one can determine the Weibull parameters on pure matrix specimens and transfer them to the matrix behaviour in the composite, if single fibre ceramic composites are used. However, it has been determined that this is not the case when textile reinforcement is used in a cementitious matrix. As will be shown in this paper, this stochastic cracking model cannot be simply transferred from single fibre ceramic composites to cementitious matrices with fibre bundles. The necessary modifications to make it useful for textile-reinforced cements are discussed.     

Use of hypar-shell structures with textile reinforced cement matrix composites in lightweight constructions

The main goal of this paper is to define a design procedure for modular, lightweight and freeform structures by quantifying the relative importance of serviceability limit states and ultimate limit states. The modular building stones of the freeform structures under study are sandwich panels with a foamed polyurethane core and TRC (textile reinforced concrete) faces, shaped in the form of hyperbolic paraboloids (hypars). The shape of these modular building stones allows the production of structural elements on a reusable doubly-curved mould. For the dimensioning of the global modular structure, two states are important according to the Eurocodes: the ultimate limit states and the serviceability limit states. Due to the lightweight aspect of the modular structure, the serviceability limit states will gain in importance: stiffness and crack formation become important factors, as does the influence of repeated loading. These factors and their influence on the final design of the proposed structures will therefore be discussed in this paper.     

单向纤维增强聚合物复合材料压缩渐进破坏单向纤维增强聚合物复合材料压缩渐进破坏

复合材料结构在承压时破坏如何演化,是其强度破坏分析的基础和核心任务。本文提出了基于连续介质损伤力学（CDM）的单向纤维增强聚合物复合材料压缩破坏渐进损伤分析（PDA）模型。建模中考虑了材料非线性行为、失效判断及损伤演化中材料性能退化等基本问题,分别对应于拉压不对称弹塑性本构关系、Puck准则、LaRC05准则及考虑破坏面方向的刚度退化方法。该模型通过用户材料子程序接口VUMAT引入到有限元软件ABAQUS中实现了有限元求解。对文献中提供的纵向、横向及偏轴压缩案例进行了数值计算并与试验数据对比。数值分析结果与试验数据吻合较好,证明了该方法的合理性和有效性,对开展多向层合板压缩破坏分析富有参考价值。      

Toughness of aromatic polymer composites reinforced with carbon fibres

This experimental study focuses on the toughness of a thermoplastic composite, namely, poly ether-ether-ketone (PEEK) reinforced with 60% by volume of continous carbon fibres (APC 2). Toughness is assessed using both comparative and intrinsic techniques and a critical discussion of the two approaches is presented.The comparative toughness of cross-ply and quasi-isotropic sheets of APC 2 is studied using a damage tolerance test (compression after impact) and by using an instrumented falling weight impacr test over a range of temperatures. Intrinsic toughness is discussed by applying fracture mechanics techniques to unidirectional laminates. Double cantilever beam and three-point flexure tests are used, the latter being performed in six different crack directions. Fracture toughness results are presented for APC 2 and unreinforced PEEK.An ultrasonic C-scan on impacted specimens and scanning electron microscopy on fracture surfaces are used to explore further the mechanisms of fracture, e.g. delamination, fibre breakage and matrix cracking.     

尼龙纤维增强纺织废胶吸声复合材料的性能

为了提高纺织废胶粉(TWRP)的回收利用的价值,首先,利用TWRP和单孔中空尼龙纤维(NF)制备了一系列NF/TWRP吸声复合材料。然后,通过动态热机械分析仪(DMA)、扫描电镜(SEM)、吸声仪及电子织物拉伸仪等仪器对复合材料的性能和微观结构进行了测试及分析。结果表明:NF的加入导致复合材料的阻尼损耗因子峰值及峰值对应的玻璃化转变温度下降;随NF含量的增加,阻尼损耗因子的峰值继续下降,而玻璃化转变温度变化不大。NF构成的中空纤维网络结构赋予了复合材料吸声性能,复合材料的刚强性得到了明显改善;NF含量越高,纤维网络结构越完善,复合材料的吸声性能就越高;复合材料的应力越大,应变越小。当NF含量为50wt%时,1mm厚的NF/TWRP复合材料在2 500 Hz下的吸声系数高达0.476;当NF含量从10wt%增加到50wt%时,NF/TWRP复合材料的应力从112.1 MPa增大到161.6 MPa,而对应的应变从136.6%变化到13.2%。所得结论为使用TWRP进行功能化开发吸声材料提供了理论基础。     

Electrical properties of carbon nanofiber reinforced multiscale polymer composites

Carbon nanofiber (CNF) reinforced epoxy matrix nanocomposites and CNF reinforced glass hollow particle filled syntactic foams are studied for electrical properties. The effect of CNF weight fraction, hollow particle volume fraction, and hollow particle wall thickness on impedance and dielectric constant are characterized. The results show that the impedance decreases and the dielectric constant increases with increasing CNF content in the composites. Nanocomposites containing 10 wt.% CNFs showed significantly higher dielectric constant because of the presence of a continuous network of CNFs in the composite. CNF reinforced syntactic foams showed higher dielectric constant than the neat resin. The CNF content had a more prominent effect on the dielectric constant than the glass hollow particle volume fraction and wall thickness. The Maxwell–Garnett and the Jayasundere–Smith models are modified to include the effect of hollow particle wall thickness and obtain predictions of dielectric constants of syntactic foams. The semi-empirical predictions obtained from Maxwell–Garnett models are closer to the experimental values. Lightweight syntactic foams, tailored for electrical properties, can be useful in electronic packaging applications.