单纤维段裂试验评述

REVIEW OF SINGLE FIBER FRAGMENTATION TEST

单纤维段裂试验作为复合材料界面剪切强度的一种测试方法被沿用至今．但是,这种方法的可信度已受到一些研究者的质疑．为了明确单纤维段裂试验的问题,本文首先对试验技术、试验结果分析等方面作了概述,并指出:纤维段裂的饱和状态是单纤维段裂试验的终点标志,以及临界长度是由试验得到的唯一数据,而这二点是这种试验方法独具的特点,同时也是这种试验方法难以克服的缺陷．在单纤维段裂试验中,按照纤维段界面端处的局部损伤模式,有3种界面端应力奇异性分析的问题需要予以考虑:(1)纤维断裂,基体没有开裂,和界面没有脱粘;(2)纤维断裂,基体开裂,但界面没有脱粘;(3)纤维断裂,界面脱粘,基体已开裂或基体未开裂．在单纤维段裂试验的界面端应力奇异性分析的基础上,本文对单纤维段裂试验的可靠性进行了研究．结论是:任何纤维和基体组成的复合材料的单纤维段裂试验都存在界面端应力奇异性,这就排除了用单纤维段裂试验测定界面剪切强度的可能性．

The single fiber fragmentation test has been used to determine the interfacial shear strength of composite materials. However, the results of the tests are subject to some controversy. With respect to the single fiber fragmentation, the test technique and reduction analysis are briefly summarized. It is noted that the single fiber fragmentation test is ended at the saturated point, and the only result obtained is the critical length. It is the inevitable drawback of the single fiber fragmentation test. In the paper, the stress singularity near the interface end is considered to evaluate the reliability of the single fiber fragmentation test. According to the local failure modes near the interface end of a fiber fragment, there are three cases to be considered for the fragmentation tests： （a） the fiber breaks only, without matrix cracking and de-bonding, （b） the fiber breaks and the matrix cracks, without interface de-bonding, （c） the fiber breaks and the interface de-bonds, with or without matrix cracking. After the singularity analysis of stress field near the interface end, it is obvious that the interfacial shear strength given by the single fiber fragmentation test is inadequate, because a stress singularity near the interface end always exists.