Elastic FEM Analysis of Fiber Push-Out Test for C/C Composites

Abstract

To study mechanical properties of fiber, matrix and their interface in C/C composites, fiber push-out test has been carried out. Where, to decompose the deformation, measured from indenter displacement, into local deformation is essential for mechanistic understandings. But up to now, there has been no systematic study on this effect. In this study, as the preliminary analysis of the push-out tests, those with a variety of groove width on specimen holder were performed and the elastic deformations of specimen were analyzed by a finite-element method (FEM). Materials used were unidirectionally reinforced C/C composites. Fiber push-out tests were carried out by utilizing dynamic ultra micro indentation test machine. For the cases of 20 and 100 μm groove, plateaus which indicate the occurrence of fiber push-out could be seen in Load-displacement curves ( indentation curves) and there was a difference in the duration of plateau. On the other hand, for all the cases, any difference could not be seen before plateaus. Now by using axis symmetrical FEM model, elastic deformation of C/C composites before push-out was calculated. From the results of calculation, the effect of groove width on indentation curves within elastic regime was considered to be little. But there was a large difference in the distribution of the stress transverse to carbon fiber direction on fiber-matrix interface between 20 and 100 μm, and this was considered to be the origin of the difference of the duration of plateau.