颗粒缺陷相互作用下复合材料的细观损伤模型

含尖角的非椭球颗粒附近应力集中较大,诱导缺陷形成裂纹是材料损伤的重要来源.对于强界面颗粒,大刚度颗粒诱导裂纹向基体中扩展形成近似平面片状裂纹,认为诱导裂纹受颗粒应力附近应力场控制,基于有效自洽理论建立了材料细观损伤模型,得到了单向拉伸下的损伤演化,并分析了颗粒形状、尺寸、颗粒性能以及颗粒与初始缺陷相对位置等因素对材料损伤的影响.结果表明,非椭球颗粒更易诱发裂纹,同样外载应力下,损伤程度更大,含非椭球颗粒材料强度更低;含扁平型的颗粒材料裂纹损伤过程更加明显并且材料强度更大;提高颗粒刚度和含量能够增大材料强度.材料中存在尺寸过大或过小的初始裂纹时材料损伤过程不明显.

MICRO-DAMAGE MODEL OF COMPOSITE MATERIALS WITH PARTICLE AND DEFECT INTERACTION 1)

Stress concentration is much bigger around the sharp angle of the non-ellipsoidal particle than around the ellipsoidal particle, and the cracks beside the particles caused by the stress are the primary damage of composite ceramics. Particle caused crack usually extends to the composite matrix to form the penny crack when the particle is stiffer than the matrix and the interface is strong. Considering the crack propagation was controlled by the stress around the particle, the meso-damage mechanical model is obtained based on the effective self-consistent theory, to describe the damage evolution of the composite ceramic under simple tension. The influences of particle shape, sizeand stiffness, and the distance between the crack and the particle on the composite damage are analyzed. The result indicated that the non-ellipsoidal particle is more easily to cause crack propagating than the similar ellipsoidal particle, and the damage degree is much higher in the composite with non-ellipsoidal particle than with non-ellipsoidal particle under the same loading. Composite strength with non-ellipsoidal particle is smaller than that with ellipsoidal particle. Stable damage process is more obvious in composite with flat particle and the strength is much higher. Increasing the particle stiffness and the particle volume fraction can improve the composite strength. The stable damage is unobvious in composite when the primary defect size is too large or too small.