Dynamic fracture behavior on 2D SiC/SiC composites

Chemically vapor infiltrated (CVI) SiC matrix composites have been fabricated from the Hi-Nicalon TM SiC based continuous fiber in the Japanese fusion materials program and its dynamic fracture behavior was studied by an instrumented impact machine using the span width of 15 mm and 17.5 mm at an impact head speed of approximately 5 m/sec to discuss the correlation between the dynamic bending tests on fracture properties and its fractography. Of significant is that the pull out property after first matrix crack (FMC) was clearly observed on the fracture surface similar to the static conventional bend tests in as received composites. Of interest is that the degradation of the composite is observed after annealed at 1500C under ultra high purity Ar flow. Two possible reason for this degradation are considered that one reason is due to the sintering occurred between the SiC fiber and the SiC matrix, the other reason is due to the self decomposition of the SiC fiber for quite low O2 partial pressure during annealing process. (author)