短纤维增强橡胶密封复合材料界面疲劳损伤行为

依据广义自洽方法,建立了包含芳纶纤维、界面相、橡胶基体和等效介质的代表性体积单元(RVE)模型。采用自定义材料子程序对内聚力疲劳累积损伤模型进行编译,分别在基体/界面相的界面和纤维/界面相的界面设置内聚力单元,研究界面相性能参数对纤维增强橡胶密封复合材料(SFRC)界面疲劳损伤行为的影响。探讨了界面相厚度和模量的确定方法,获得了不同界面相厚度和模量下SFRC界面脱粘起始位置以及脱粘起始疲劳次数。结果表明,较低的界面相模量能够抑制界面脱粘的产生;随着界面相厚度的增加,界面脱粘的起始疲劳次数增加,SFRC抗疲劳损伤能力得到提高。     

界面相性态对纤维增强复合材料内应力传递的影响

本文用有限元法研究了具有基体裂纹的纤维增强复合材料内的应力传递问题。假设纤维与基体的界面为非理想的，文中运用“弹簧层”模型首先分析了在不同的组分弹性模量比、纤维体积含量与边界约束条件下，界面相性态对复合材料的应力传宾影响，然后进一步考察了在几种典型的损伤模式下界面附近的应力分布情况。     

原子力显微镜表征纤维增强聚合物复合材料的界面相概述

纤维增强聚合物复合材料(FRPC)的界面相是一个尺度只有几十纳米到几微米之间的微小区域,是复合材料中应力传递的枢纽,对复合材料的整体性能起着至关重要的作用。因此,急需寻求一种高分辨率的纳米探测技术来表征该区域并研究其性能,这对复合材料的结构设计有着重要的科学意义和指导作用。文章概述了几种原子力显微镜(AFM)常见应用模式,并且阐述了采用AFM表征FRPC界面相的研究现状,总结了目前存在的问题并提出未来的研究方向。     

界面相性态对纤维增强复合材料内应力传递的影响

本文用有限元法研究了具有基体裂纹的纤维增强复合材料内的应力传递问题.假设纤维与基体的界面为非理想的,文中运用“弹簧层”模型首先分析了在不同的组分弹性模量比、纤维体积含量与边界约束条件下,界面相性态对复合材料内的应力传递的影响,然后进一步考察了在几种典型的损伤模式下界面附近的应力分布情况.     

含脆性界面相的颗粒增强金属基复合材料的损伤

通过引入双夹杂模型,将传统增量损伤理论扩展应用到三相复合材料颗粒尺寸效应问题,同时提出一个可以研究颗粒增强金属基复合材料的弹塑性变形及渐进式脱黏损伤模型,该模型还可以研究含脆性界面相的颗粒增强金属基复合材料弹塑性损伤变形行为的颗粒尺寸效应。研究发现,包含各种不同颗粒尺寸的颗粒增强金属基复合材料的脱黏损伤按照颗粒尺寸从大到小的顺序先后发生,并且该模型与SiC/Al复合材料的试验结果比较一致。     

含界面相的单向纤维增强复合材料三维应力场的二重双尺度方法

提出了计算含界面相的单向纤维增强复合材料三维应力的二重双尺度方法。在性能预报方面,首先对界面相和纤维进行均匀化得到均匀化夹杂,然后对均匀化夹杂和基体进行均匀化得到宏观均匀材料;在应力场描述方面,从宏观均匀场出发,利用双尺度渐近展开技术经过两次应力场传递,依次得到单胞和应力集中区域的应力场。与有限元方法相结合,计算了宏观轴向均匀拉伸载荷条件下含界面相的单向纤维增强复合材料的三维应力场分布。数值结果表明在此载荷条件下最大应力发生在每根纤维的中截面内,靠近纤维与界面相的交界处。讨论了界面相性能对应力场分布的影响,结果显示纤维、界面相与基体力学性能的等差过渡有利于缓解纤维在界面附近的应力集中。      

连续分布界面相对SiCp/Al复合材料热导率影响的数值模拟

采用有限元方法对SiCp/Al复合材料的导热性能进行了数值模拟, 建立了含界面相颗粒增强铝基复合材料测试模型, 研究了不同界面相种类、厚度对复合材料热导率的影响。结果表明: 当界面相与SiC/Al结合理想时, 且界面相在颗粒表面呈连续分布时, 复合材料热导率随着界面层热导率的增加而增大, 但增加的幅度由快变慢; 复合材料热导率随界面层厚度的变化取决于界面层厚度t与颗粒粒径a的比值, 当t/a很小或t/a较大时, 热导率随界面层厚度的变化很小, 当t/a较小时, 热导率随界面层厚度的变化则与界面层热导率有关。     

PyC/SiC界面相对PIP法制备3D HTA C/SiC复合材料性能的影响

利用三维编织炭纤维预制件通过先驱体浸渍裂解法制备C／SiC复合材料。研究了热解碳（PyC）／SiC界面相对复合材料的微观结构和力学性能的影响。弯曲性能通过三点弯曲法测试，复合材料的断口和抛光面通过扫描电镜观察。结果表明：通过等温化学气相沉积法在纤维表面沉积PyC／SiC界面相以后，复合材料的三点抗弯强度从46MPa提高到247MPa。沉积界面的复合材料断口有明显的纤维拔出现象，纤维与基体之间的结合强度适当，起到了增韧作用；而未沉积界面相复合材料的断口光滑、平整，几乎没有纤维拔出，纤维在热解过程中受到严重的化学损伤，性能下降严重，材料表现为典型的脆性断裂。     

预测纤维复合材料有效模量的分级模型

为纤维复合材料的有效模量计算建立了一个宏观与细观相结合的分级模型: 即假定共焦点椭圆柱组合体的纤维/基体细观结构单元嵌在宏观上均匀化了的复合材料中。利用解析函数的保角变换与罗朗级数展开, 获得了轴向剪切模量的封闭公式。理论值与实验值吻合很好, 克服了经典模型理论与实验结果偏差太大的缺点。      

含界面相三维全五向编织复合材料拉伸行为模拟及失效机制研究

基于三维全五向（Q5D）编织复合材料的细观结构模型,通过引入界面相单元,建立了含界面相Q5D编织复合材料单轴拉伸损伤失效分析模型。应用Python语言实现对ABAQUS的二次开发,将Linde等提出的失效准则和Von-Mises应力准则分别用于纱线和基体的渐进损伤判断,并确定材料的整体失效模式;对于界面相,采用Quads准则进行损伤判断。利用周期性位移边界条件,对含界面相Q5D编织复合材料的纵向拉伸应力-应变行为进行了渐进损伤数值模拟,详细讨论了在纵向拉伸载荷作用下材料的细观损伤起始、扩展和最终失效的演化过程,分析了材料的细观损伤失效机制,预测了材料的极限破坏强度,并研究了界面相性能对材料整体力学行为的影响规律。研究结果表明,数值模拟结果与实验值吻合较好,验证了渐进损伤模型的有效性,为该类材料的力学分析和优化设计奠定了基础。     

预报纤维增强复合材料有效热导率的随机微结构胞元模型

发展了能预报复合材料有效性质的随机微结构胞元模型以预测单向纤维增强复合材料横向热导率。研究了能反映宏观有效性质的模型最小化问题, 探讨了微结构影响宏观有效热传导性能的机制。结果表明: 通过对模型指定周期边界条件并且以多个合适的小规模模型计算的平均值取代大模型计算, 可大大改进收敛性并提高计算效率, 从10×10个到30×30个子胞的模型, 所得有效热导率计算结果的最大相对变化量仅为0.6%。不同纤维排列引起热流穿过热阻大的基体的路径长度改变, 造成有效热导率不同; 纤维热导率远大于基体热导率时, 纤维随机分布造成纤维偏聚, 部分纤维接触形成"热流通道", 使得有效热导率增大, 揭示了某一体积分数下有效热导率急剧增加是由"热流通道"贯通引起。与实验结果的比较说明了微结构随机性研究的必要性和本文工作的实用价值。     

A micro-mechanics model for composites reinforced by regularly distributed particles with an inhomogeneous interphase

Based on the Mori–Tanaka method, a micro-mechanics model is developed to study the effective elastic properties of composites reinforced by regularly distributed particles. The spatial distribution of particles is supposed to be cube symmetric in the three-dimensional space, and the corresponding finite element method (FEM) computation has been performed through a unit cell model. Additionally, particle interaction and distribution are simultaneously taken into account by using the strain Green’s function, and the specified strain Green’s function is determined by utilizing the necessary conditions of geometric symmetry. In order to analyze particle size effect on the effective properties of composites, the Double-inclusion configuration and related theory are introduced to describe the role of the interphase between the matrix and particles. Finally, the overall elastic properties of the composite with regularly distributed particles are described by three independent elastic constants expressed in the explicit form, and the accuracy of the developed model is verified by comparing with FEM results.     

Application of MFS for determination of effective thermal conductivity of unidirectional composites with linearly temperature dependent conductivity of constituents

In this paper the problem of the effective conductivity in composite material is considered. It is assumed that the thermal conductivity coefficients of both the matrix and fibres materials are temperature-dependent. It yields the temperature-dependency of the effective thermal conductivity. To determine the effective thermal conductivity a unit-cell approach is used, i.e. heat flow in repeated element, which consists of one fibre in the matrix, is considered. It leads to 2-D nonlinear boundary value problems in matrix and fibre regions. In the paper, it is proposed to solve the given nonlinear boundary value problem by Picard iteration. For every iteration step, the linear boundary value problem with two uncoupled linear partially differential equations and coupled boundary conditions is solved. The method of fundamental solution, supported by radial basis functions approximation, is implemented to obtain the required solutions. The numerical experiment has been performed. The results of the experiment and some conclusions are included as well.     

Modeling the thermal conductivity of diamond reinforced aluminium matrix composites with inhomogeneous interfacial conductance

A reasonable model for describing the thermal conductivity of diamond reinforced aluminium matrix composites behaving a distinctive character of inhomogeneous distribution of interfacial thermal conductance on diamond surfaces is proposed in terms of an equivalent diameter approach combined with a double effective-medium approximation scheme. Theoretical analyses for the thermal conductivity of diamond reinforced Al (Si) composites prepared by different infiltration techniques (squeeze casting (SQ), gas pressure infiltration (GPI)) are given for rediscovering the existing experimental results considering inhomogeneous conductance behavior. Numerical results using present model agree reasonably well with the experimental observations and explore new findings, i.e. the diffusion bonding also occurs at Al–diamond {1 1 1} interfaces of GPIed composites; the interconnected particles is possibly existed in GPIed Al/diamond composites.     

颗粒弥散复合材料等效导热系数的估算

等效热导率是热障功能梯度材料的重要热物理性能,本文采用小最小热阻力法则和比等效导热系数相等法则,推导出了热障型陶瓷／金属复赤道儿热导系数的普通式。并研究了Ni-ZrO2系复合材料的等效热导率随成分变化的规律,将理论值和实测值进行了比较。结果表明该理论对热障功能梯度材料的设计具有指导意义。     

周期性复合材料等效传热系数预测的渐进均匀化新算法及其实现

渐进均匀化方法具有严格的数学基础,预测周期性复合材料的等效热传导系数具有较高的计算精度。本文提出了基于渐进均匀化方法预测周期性复合材料等效热传导系数的新算法。相比原有的算法具有两个优点：它的实现与代表体元方法一样简单,新的算法以现有的有限元商业软件为黑箱,通过简单的几个分析步骤,即可以获得复合材料的等效热传导系数;可以利用商业软件提供的多种单元类型去离散同一个单胞,在处理复杂几何单胞结构时,可以节约大量的计算费用。通过几个典型的算例,验证了方法的有效性。该工作对于推广渐进均匀化方法在预测复合材料等效热传导系数的广泛应用具有积极作用。     

高导热炭纤维及其炭基复合材料

主要介绍了国际上近十年来高导热炭纤维（CF）及其炭基复合材料发展的新动向。     

Bounds on the effective thermal conductivity of composites with imperfect interface

A new model is developed to bound the effective thermal conductivity of composites with thermal contact resistance between spherical inclusions and matrix. To construct the trial temperature and heat flux fields which satisfy the necessary interface conditions, the transition layer for each spherical inclusion is introduced. For the upper bound, the trial temperature field needs to satisfy the thermal contact resistance conditions between spherical inclusions and transition layers and the continuous interface conditions between transition layers and remnant matrix. For the lower bound, the trial heat flux field needs to satisfy the continuous interface conditions between different regions. It should be pointed out that the continuous interface conditions mentioned above are absolutely necessary for the application of variational principles, and the thermal contact resistance conditions between spherical inclusions and transition layers are suggested by the author. According to the principles of minimum potential energy and minimum complementary energy, the bounds of the effective thermal conductivity of composites with imperfect interfaces are rigorously derived. The effects of the size and distribution of spherical inclusions on the bounds of the effective thermal conductivity of composites are analyzed. It should be shown that the present method is simple and does not need to calculate the complex integrals of multi-point correlation functions. Meanwhile, the present method provides an entirely different way to bound the effective thermal conductivity of composites with imperfect interface, which can be developed to obtain a series of bounds by taking different trial temperature and heat flux fields. In addition, the present upper and lower bounds are finite when the thermal conductivity of spherical inclusions tends to ∞ and 0, respectively.     

Rigorous bounds on the effective thermal conductivity of composites with ellipsoidal inclusions

A new method is developed to derive the bounds of the effective thermal conductivity of composites with ellipsoidal inclusions. The transition layer for each ellipsoidal inclusion is introduced to make the trial temperature field for the upper bound and the trial heat flux field for the lower bound satisfy the continuous interface conditions which are absolutely necessary for the application of variational principles. According to the principles of minimum potential energy and minimum complementary energy, the bounds of the effective thermal conductivity of composites with ellipsoidal inclusions are rigorously derived. The effects of the distribution and geometric parameters of ellipsoidal inclusions on the bounds of the effective thermal conductivity of composites are analyzed. It should be shown that the present method is simple and needs not calculate the complex integrals of multi-point correlation functions. Meanwhile, the present method provides a powerful way to bound the effective thermal conductivity of composites, which can be developed to obtain a series of bounds by taking different trial temperature and heat flux fields. In addition, the present upper and lower bounds still are finite when the thermal conductivity of ellipsoidal inclusions tends to ∞ and 0, respectively.     

填料型高导热复合材料的研究现状与发展趋势

填料型导热复合材料是LED等半导体在封装及使用过程中一种常见的散热材料,它利用高导热填料填充具有密度小、可加工性能好、成本低廉等优点的高分子聚合物制备而成,对降低半导体器件的结温、增强其综合特性大有裨益。简要概述了近年来填料型导热复合材料的研究现状,并对其发展趋势进行了预测,以期为LED的实际散热需要提供技术参考,进而推动LED产业的发展。