纤维复合材料的弹粘塑性行为体分比与应变率的影响

利用微观力学方法研究了纤维增复合材料的弹塑性行为，着重分析了纤维体分比和加载应变率对以金属基为主的复合材料应力－应变关系的影响。给出了不同体分比的Ｇｒａｐｈｉｔｅ／Ｔｉｔａｎｉｕｍ复合材料在不同常应变率下的应力－应变关系曲线，对这两种因素的影响进行了比较分析。     

Exact Results for the Homogenization of Elastic Fiber-Reinforced Solids at Finite Strain

This work is concerned with the homogenization of solids reinforced by aligned parallel continuous fibers or weakened by aligned parallel cylindrical pores and undergoing large deformations. By alternatively exploiting the nominal and material formulations of the corresponding homogenization problem and by applying the implicit function theorem, it is shown that locally homogeneous deformations can be produced in such inhomogeneous materials and form a differentiable manifold. For every macroscopic strain associated to a locally homogeneous deformation field, the effective nominal or material stress–strain relation is exactly determined and connections are also exactly established between the effective nominal and material elastic tangent moduli. These results are microstructure-independent in the sense that they hold irrespectively of the transverse geometry and distribution of the fibers or pores. A porous medium consisting of a compressible Mooney–Rivlin material with cylindrical pores is studied in detail to illustrate the general results. This work was the first time presented at the Euromech Colloqium 464 on “Fiber-reinforced Solids: Constitutive Laws and Instabilities”, September 28–October 1, 2004, Cantabria, Spain.     

A PREDICTIVE APPROACH TO THE IN-PLANE MECHANICAL PROPERTIES OF STITCHED COMPOSITE LAMINATES

This contribution attempts to model the alteration of the in-plane elastic properties in laminates caused by stitching,and to predict the in-plane effective tensile strength of the stitched composite laminates.The distortion of in-plane fibers is considered to be the main cause that affects the in-plane mechanical properties.A fiber distortion model is proposed to characterize the fiber misalignment and the fiber content concentration due to stitching.The undistorted region,the fiber distortion region,the resin-rich pocket and the through-thickness reinforcement section are taken into account.The fiber misalignment and inhomogeneous fiber content due to stitching have been formulated by introducing two parameters,the distortion width and maximum misalignment.It has been found that the ply stress concentration in stitched laminates is influenced by the two concurrent factors,the stitch hole and inhomogeneous fiber content.The stitch hole brings about the stress concentration whereas the higher fiber content at the local region induced by stitching restrains the local deformation of the composite.The model is used to predict the tensile strength of the [0/45/0/-45/90/45/0/-45]_(2s) T300/QY9512 composite laminate stitched by Kevlar 29 yarn with different stitching configurations,showing an acceptable agreement with experimental data.     

含材料非线性的复合材料单钉接头累积损伤分析

发展了静拉伸复合材料接头层合板三维逐渐损伤模型,考虑了单层复合材料在材料1-2面及3-1面上具有明显非线性剪切应力-应变关系的叠层非线性效应,结合有限元技术即应力分析、失效判定准则及损伤过程中材料性能退化等,对接头层合板损伤扩展进行了模拟,结果表明考虑材料非线性的影响与实验结果吻合更好.     

Multigrid Models of Composite Materials of Irregular Structure with a Small Filling Ratio

This paper considers composites consisting of a set of typical composite multigrid finite elements whose structures are regular and different. Mean local errors are proposed for multigrid modeling of composites.     

含夹杂和微裂纹复合材料的损伤演化和分析

利用细观力学的Ｅｓｈｅｌｂｙ和Ｍｏｒｉ－Ｔａｎａｋａ理论，考虑纤维和微裂纹之间的相互作用，研究了定向分布微裂纹的演化规律及其对材料力学性能的影响，分析了纤维体积份数，弹性系数、微裂纹密度，纤维不同取向与基体开裂强度之间的变化关系，并给出了许多有意义的结论。     

ANISOTROPIC EFFECTS OF QUASI-ISOTROPIC COMPOSITES(I)──MODELLING

Experimental observations show that quasi-isotropic materials, such as N-axial fibre-reinforced composites and woven materials, exhibit various degrees of anisotropy in elasticity and strength, and the anisotropy in strength is normally stronger than that in elasticity. In view of some available experimental data and based on the general formulation of the constitutive equations and failure criteria of quasi-isotropic materials established by using the theory of representations for tensor functions, we postulate several applicable models of the constitutive equations and strength for 3-and 4-axial quasi-isotropic materials to reveal the anisotropic effects. In a continued work (Part II), the anisotropic effect in strength of an infinitely large plate with a single elliptical hole or crack is studied, and the proposed stiffness and strength models are verified in terms of micro-mechanical analyses.Project supported by the National Natural Science Foundation of China and the State Education Commission Foundation of China     

用云纹干涉法测量带孔复合材料板应变系数

介绍云纹干涉法在复合材料中应用的一个例子，用云纹干涉法测量带孔复合材料板应变集中系数．     

石墨对铜基自润滑材料高温摩擦磨损性能的影响

通过基体多元合金化和选用不同粒度的石墨颗粒,采用常规粉末冶金方法制备了铜基石墨固体自润滑材料,在大越式OAT-U型摩擦磨损试验机上考察了复合材料从室温到500℃温度条件下的摩擦磨损性能,利用扫描电子显微镜观察分析磨损表面形貌,进而探讨其摩擦磨损机理.结果表明:在室温条件下,石墨颗粒越小,则复合材料的摩擦系数越小,减摩自润滑效果越好;在室温至500℃条件下,选用合适的石墨粒度(0.3～0.5mm)和多元基体合金化,可使铜基石墨固体自润滑材料保持较好的自润滑特性.     

复合材料层合板冲击损伤及剩余强度分析方法

应用三维逐渐累积损伤理论和分析技术对层合板的冲击及冲击后含损伤的层合板在拉伸载荷下损伤扩展的全过程进行分析.分析中取消了以往研究者对冲击后层合板损伤状态所做的人为假设,将冲击后层合板的实际损伤状态直接用于剩余拉伸强度研究.通过与已有文献结果比较,验证了方法的正确性.