Stress and Failure Analysis of Brittle Matrix Composites. Part II: Failure Analysis

A linear elastic fracture mechanics analysis of a cylindrical element of matrix with a single fiber and two matrix annular cracks perpendicular to the fiber direction under longitudinal tensile load was undertaken. The order of singularity and the angular dependence of the stress field in the neighborhood of the crack periphery were determined by using the stress function approach proposed by Zak and Williams. The stress intensity factor was evaluated by combining the results of the local stress solution with a finite element analysis. The case of fiber debonding originating from the periphery of the annular cracks was also studied. For that problem both opening-mode and sliding-mode stress intensity factors and the strain energy release rate were determined. These results help to understand the various failure mechanisms including matrix cracking, debonding along interfaces and kinking of interface cracks into fibers in brittle matrix composites. This revised version was published online in July 2006 with corrections to the Cover Date.     

Numerical Analysis of Stress Concentration for Brittle Matrix Composites

A FEM numerical model is constructed of SiCf/LASIII glass-ceramic uni-direction plate under tension loading. The smeared crack method is used to deal with the failure point of fiber and matrix elements. The solution of the model gives the distribution of meso-stress of SiCf/LASIII glass-ceramic uni-direction plate. The stress concentration factor K and the size of stress concentration effect zone are also analyzed. The average saturation cracking space is obtained by a numerical method. The mesh length of the elements is also studied.     

基于代表性体积单元的双模铝基复合材料性能拟实研究

目的 研究双模铝基复合材料连续区(Continuous Region,CR)和非连续区(Discontinuous Region,DR)力学性能对材料整体力学性能的影响规律,以深入了解双模铝基复合材料的强韧化机理。方法 基于Abaqus模拟软件,以双模CNT/Al为研究对象,建立了构型尺度的代表性体积单元(RVE)模型,采用GTN(Gurson-Tvergaard-Needleman)模型来描述双模CNT/Al中CR和DR的变形力学行为,通过定义力学性能参数来简化描述CR和DR复杂的力学性能。针对双模CNT/Al的CR和DR,分别设定力学性能参数HC和HD,并进行一系列的拉伸载荷模拟,研究HC和HD对双模复合材料整体力学性能的影响规律。通过与真实双模CNT/Al的力学性能进行对比,得到双模CNT/Al中CR和DR力学性能与均匀材料力学性能的差异,最后对双模CNT/Al在变形过程中的应力分布情况和断裂后的形貌进行分析。结果 当HC小于4时,双模CNT/Al的抗拉强度随HD的增大而下降;当HC大于5时,双模CNT/Al的抗拉强度随HD的增大而增大;双模CNT/Al的屈服强度随着HD和HC的增大而增大,延伸率随着HD和HC的增大而降低。当HD或HC一定时,在HC=HD时,模型材料的延伸率最大。典型双模CNT/Al由“粗晶铝合金+CNT/超细晶Al复合材料”构成,与均匀结构的粗晶铝合金相比,其构型中粗晶铝合金的强度显著提升、塑韧性显著下降;与均匀结构的CNT/超细晶Al相比,其构型中的CNT/超细晶Al复合材料的强度小幅降低、塑韧性小幅提升。当HD大于HC时,裂纹优先在DR产生;当HD小于HC时,裂纹优先在CR区产生;当HD和HC接近时,裂纹产生的区域更加分散。结论 建立了一种双模铝基复合材料的有限元模型,从数值上说明了双模CNT/Al复合材料微区与均匀材料的力学性能存在显著差异,为双模铝基复合材料的设计提供了参考。     

高温下的金属基复合材料双剪切试样应力应变有限元分析

对金属基复合材料双剪切试样的应力应变分布进行蠕变有限元计算分析,得到受剪区的应力应变随时间的分布规律。通过典型取向试样分析,表明受剪区的应力应变与纤维随机分布平面和加载方向夹角θ之间存在很大的相关性:随角度θ的减小,其蠕变应力分布越均匀;当角度θ=45°时,其稳态蠕变率γ·最大。双剪切试样能得到较均匀的剪应力区域,适合研究材料纯剪应力状态下的蠕变行为。     

Indentation Plastometry of Particulate Metal Matrix Composites,Highlighting Effects of Microstructural Scale

Herein, it is concerned with the use of profilometry-based indentation plastometry (PIP) to obtain mechanical property information for particulate metal matrix composites (MMCs). This type of test, together with conventional uniaxial testing, has been applied to four different MMCs (produced with various particulate contents and processing conditions). It is shown that reliable stress–strain curves can be obtained using PIP, although the possibility of premature (prenecking) fracture should be noted. Close attention is paid to scale effects. As a consequence of variations in local spatial distributions of particulate, the “representative volume” of these materials can be relatively large. This can lead to a certain amount of scatter in PIP profiles and it is advisable to carry out a number of repeat PIP tests in order to obtain macroscopic properties. Nevertheless, it is shown that PIP testing can reliably detect the relatively minor (macroscopic) anisotropy exhibited by forged materials of this type.     

铝基复合材料应力传递的有限元分析

本文使用大型有限元分析软件Ansys建立了短纤维增强铝基复合材料的有限元模型,模拟复合材料界面上的应力应变分布,进一步详细分析了纤维的不同参数对纤维使用效率的影响,以及不同纤维弹性模量的匹配对应力传递的影响。     

国内外碳/碳复合材料连接研究进展

介绍了近年来国内外碳/碳复合材料连接领域的研究进展,系统总结了碳/碳复合材料与自身及其与铜合金、钛合金、铌合金之间连接新技术与新工艺,并对有限元分析方法在碳/碳复合材料连接中的应用进行了简要的概括.针对碳/碳复合材料连接中存在的问题,提出了一些可行性解决方案,最后展望了碳/碳复合材料连接的研究前景.     

金属基复合材料弹性模量的研究现状

综述了金属基复合材料弹性模量的影响因素,介绍了几种金属基复合材料弹性模量的理论计算公式和预测方法,阐述了测量金属基复合材料弹性模量的方法.     

Experimental and Numerical Investigations on the Ballistic Performance of Polymer Matrix Composites Used in Armor Design

Ballistic properties of two different polymer matrix composites used for military and non-military purposes are investigated in this study. Backside deformation and penetration speed are determined experimentally and numerically for Kevlar 29/Polivnyl Butyral and Polyethylene fiber composites because designing armors for only penetration is not enough for protection. After experimental ballistic tests, a model is constructed using finite element program, Abaqus. The backside deformation and penetration speed are determined numerically. It is found that the experimental and numeric results are in agreement and Polyethylene fiber composite has much better ballistic limit, the backside deformation, and penetration speed than those of Kevlar 29/Polivnyl Butyral composite if areal densities are considered.     

单向C/SiC陶瓷基复合材料基体失效机制与强度预测

采用细观力学方法对单向C/SiC陶瓷基复合材料的基体失效机制进行了研究。利用剪滞理论模型和临界基体应变能(CMSE)准则预测了C/SiC陶瓷基复合材料受拉时基体开裂失效过程,获得了单向C/SiC陶瓷基复合材料基体开裂段的应力-应变曲线。并将扩展有限元法(XFEM)用于该开裂过程的模拟,得到了对应的应力-应变曲线。研究结果表明,采用剪滞理论模型、CMSE和采用XFEM得到的计算结果与相关的实验结果三者能较好地吻合,证明了计算方法的有效性。     

W与CuCrZr焊接应力的有限元分析及剪切强度的研究

为了研究应用于聚变试验堆的面向等离子体部件中W与CuCrZr的焊接,选用有限元软件ABAQUS对未用无氧铜箔、或使用不同厚度的无氧铜箔,及在不同温度、压力时的焊接应力进行了有限元分析。实验中使用、或未用无氧铜中间层均成功实现了W与CuCrZr的焊接。测定了焊接试样的剪切强度,并通过SEM观察了其断口形貌。实验结果表明,无氧铜箔的使用大大地提高了焊接强度,最高剪切强度高于198MPa,其剪切断口均位于距离焊缝1mm左右的钨块中,且在钨块中均出现了撕裂现象。ABAQUS有限元数值分析的结果表明,无氧铜箔很好地降低了W与CuCrZr之间的焊接应力,较低的焊接温度、较高的焊接压力、增加无氧铜箔的厚度均有助于减小W与CuCrZr之间的焊接应力。     

纤维增强陶瓷复合材料的工艺热失配应力分析EI

在弹性力学圆筒理论和剪滞模型的基础上，依据考虑界面相和界面层效应的力学简化模型，分两种情况具体讨论复合材料制备过程中由于降温落差大小造成的工艺残余应力，并与Ｂｕｄｉａｎｓｋｙ等人的结果作了对比讨论。第一种情况考虑了界面层剪切效应，第二种略去了界面层剪切效应。为了更清楚地了解界面间正压力与剥离力之间的区别，分αｆ＞αｍ和αｆ＜αｍ两种情况来分析。     

碳纳米管增强镁基复合材料强化机制的解析法研究

采用剪切滞后模型理论分析了碳纳米管增强镁基复合材料受载时作用在复合材料上各组分的应力;考虑复合材料各种强化机制,建立碳纳米管增强镁基复合材料的屈服强度模型,研究了各组分性能参数对复合材料屈服强度的影响。结果表明,CNTs的长度对CNTs/Mg复合材料屈服强度的影响有限;碳纳米管层数越多或分散越稀疏越不利于提高复合材料的屈服强度;在一定范围内屈服强度随着温度差的增加而增加;CNTs的体积分数对复合材料屈服强度的影响存在最佳值。这表明该模型预测的复合材料屈服强度与实验结果较吻合。     

碳纤维树脂基复合材料及成型工艺与应用研究进展

目的 碳纤维树脂基复合材料的可设计性和性能优越性使得碳纤维及其树脂基复合材料的应用范围不断拓展.文章简述了碳纤维的性能、发展和分类,研究碳纤维树脂基复合材料的性能影响因素、成型工艺及应用领域,探索其未来研究的发展方向.方法 采用文献调研法,梳理和汇总国内外关于碳纤维树脂基复合材料的制备及应用研究,分析国内外关于其性能影响因素、成型工艺和应用领域的研究进展.结论 碳纤维树脂基复合材料性能受碳纤维含量、基体和碳纤维界面结合性能等因素的影响.国内碳纤维树脂基复合材料的成型技术主要以传统成型工艺为主,不同性能要求和结构特点的构件采用不同成型工艺.应用范围从航空航天、军工领域不断拓展至民用领域,生产制备的高效能化和低成本化是其未来发展方向.此外,环境问题及碳纤维的回收利用是未来碳纤维及其复合材料应用的关键问题.     

镁基复合材料热膨胀的研究进展和前景展望

简要介绍了镁合金及镁基复合材料热膨胀的研究进展,叙述了温度、增强体体积分数、增强体颗粒尺寸、增强体颗粒形状、增强体种类和热处理及其他对镁基复合材料热膨胀的影响。简要介绍了热膨胀的理论预测模型,并对今后的发展做了展望。     

颗粒增强金属基复合材料的结构建模与力学模拟研究进展

颗粒增强金属基复合材料具有高模量、高强度及高耐磨等优异性能,其材料体系庞杂、复合结构繁复,力学性能指标众多。通过结构建模与力学模拟的系统研究,能够有效揭示复合材料的构效关系与组织演变规律,进而指导其设计、制备、加工与应用全流程研究。开展多尺度建模计算,并与宏、微观实验相融合,以及利用以数据库技术、高通量计算与大数据挖掘为主要特征的材料信息学研究,可实现金属基复合材料的“组分-工艺-结构-性能”内禀关系的科学内涵描述。首先回顾了颗粒增强金属基复合材料建模计算的主要研究方法,然后对其结构建模研究现状进行了介绍,进而围绕界面特性与力学模拟进行了综合述评,最后对建模拟实结合材料基因工程技术的未来发展进行了展望。     

Property Modeling across Transition Temperatures in PMC's: Part I. Tensile Properties

Numerous studies report the effects of temperature on the stiffness and strength of polymer matrix composites (PMC's). Due to the complexity of the relaxation phenomenon in the matrix, these studies are mainly qualitative. In the present paper models were developed that can explicitly relate the mechanical response of the composite to temperature. These models are related to the microstructure of the constituents, and therefore can be applied to any polymer matrix composite. The possibility of using these models was illustrated by the study of the mechanical behavior of carbon fiber AS4/polyphenylene sulfide (PPS) at elevated temperatures. Part I of this paper relates to the modeling of the temperature-dependent composite tensile properties (stiffness and strength). Parts II and III focus on the life prediction of AS4/PPS undergoing static and fatigue end-loaded bending at elevated temperatures.     

SiCf/TC17复合材料界面剪切强度测试与有限元分析

界面强度对钛基复合材料的性能有重要影响。采用纤维顶出实验(push-outtest)对连续SiC纤维增强TC17复合材料的界面剪切强度进行了测试,采用SEM观察了样品的形貌。以纤维/基体完全分离后的摩擦力为出发点,采用有限元方法确定了复合材料成型过程中残余应力的产生温度,并计算了残余应力的分布,比较了顶出实验样品制备前后残余应力的变化情况及样品厚度、体积分数对残余应力分布的影响;采用内聚力模型(CZM)分析了界面的化学结合强度。结果表明:SiCf/TC17复合材料高温成型后的冷却过程中开始产生残余应力的温度为775℃;顶出实验样品制备后界面处生成了残余剪切应力,其大小和分布与样品的体积分数和厚度相关,界面处的残余剪切应力造成了界面剪切强度的测试结果与界面化学结合强度的差异;室温下SiCf/TC17复合材料的界面化学结合强度约为450MPa。     

Fatigue damage mechanics of composite materials Part III: Prediction of post-fatigue strength

A damage-based model for post-fatigue notch strength is presented. The model is an extension of a method developed previously to predict the notch strength of laminated composites. A simple finite element representation of the notch tip damage zone is used to obtain the localized damage-modified stress distribution. A uniaxial tensile stress failure criterion is applied to the 0° plies from which the laminate strength is evaluated. In conjunction with the fatigue damage growth law described in Part II, residual strength is calculated as a function of the applied loading conditions, specimen geometry and lay-up for (90/0)_s, (90/0)_2s and (90₂/0₂)_s T300/914C carbon-fibre/epoxy laminates subjected to tension-tension fatigue cycling.     

Statistical Analysis of Reinforcement Characterization in SiC Particle Reinforced Al Matrix Composites

The characterization of reinforcement in 15% SiC particles reinforced Al matrix composites processed by powder metallurgy route was studied by statistical method. During the analysis, a new approach for the estimation of the characterization of reinforcement was presented. The mathematic software MATLAB was used to calculate the area and perimeter of reinforcement, in which the image processing technique was applied. Based on the calculation, the fractal dimension, shape factor, reinforcement size distribut...