SiC晶须及原位增强Si3N4基复合材料的断裂过程

探讨了ＳｉＣ晶须增强和β－ｓｉａｌｏｎ细长晶粒原位增强Ｓｉ３Ｎ４基复合材料的断裂过程。２种材料的试验结果都显示出明显的二级增韧行为：一级增韧过程，断裂阻抗ＫＲ随微小的裂纹扩展而急剧增大，大裂纹扩展到大约０．２５ｍｍ时达到饱和；二级增韧过程，ＫＲ缓慢增长，一直持续到裂纹扩展达到１ｍｍ（原位增强）和１．８ｍｍ（晶须增强），观察和分析表明：二级增韧行为的发生，本质上起因于裂纹尖端后方桥接晶须和细长晶粒与

FRACTURE PROCESS OF SiC_WHISKER_REINFORCED AND IN_SITU REINFORCED Si3N4 COMPOSITES

Fracture resistance process of SiC_whisker_reinforced and in_situ reinforced Si 3N 4 composites was explored. The experimental results of both the materials show considerable two_step toughening behavior. In the first toughening process, the fracture resistance K R increases quickly with crack extension, and becomes constant when the crack extension is about 0.25 mm; while in the secondary toughening process K R gradually increase, until the crack extension reaches 1 mm (for in_situ reinforcement) and 1.8 mm (for whisker reinforcement). The observations and the analyses indicate that, the two_step toughening behavior results essentially from the further debonding of the whisker-matrix interfaces (or the grain boundaries) in the crack bridging zone behind the crack tip , and the orientation angle of the whiskers (or the elongated grains) with respected to the normal direction of crack surface was the dominant cause for the further debonding.