Notch sensitivity of C/C-SiC composite evaluated by flexural tests

Abstract

The notch effects on the mechanical behavior of Liquid Silicon Infiltration (LSI) based continuous carbon fiber reinforced silicon carbide (C/C-SiC) was studied. The in-plane (IP) and out-of-plane (OP) flexural properties of notched and unnotched samples with fiber orientations (0°, 45° and 60°) were determined through 3-point-bending (3PB) and single notched beam (SENB) tests. Despite the significant difference in bending modulus, the strength depends only slightly on the fiber orientation and loading direction, which could be explained through the uneven distribution of SiC-matrix within the block-like structure of C/C-SiC. This unique micro-structure also leads to a relatively constant value of notch sensitivity in the IP direction, and the sensitivity to the notch is relatively low for all tested C/C-SiC specimen configurations. Furthermore, due to the large differences of fracture mechanism, the work of fracture (WOF) in the IP direction is significantly smaller than in the OP direction for all fiber orientations.