Microdamage in SiC fiber-reinforced glass matrix composite by repeated thermal shocks

Continuous SiC fiber (Nicalon(TM)) fiber-reinforced glass matrix composite was studied on microdamage evolution process by repeated thermal shocks at Delta T=700 and 800 K. The composite was subjected to the shock up to five times. The multiple matrix crackings perpendicular to the fiber axis were observed at the surface and the number of crackings increased with the number of cycles, however, their depths were unchanged, The damage did not occurred at Delta T=700 K while damage occurred at Delta T=800 K and this temperature difference was about 400 K higher than the damage initiation temperature difference of a monolithic glass matrix. Cracks parallel to through the thickness direction were also observed and the number of cracks increased with the increase of N. The characteristics of damage evolution process of the composite were discussed based on a set of the experimental evidences.