Experimental and numerical evaluation of bending and tensile behaviour of carbon-fibre reinforced SiC

The tensile and bending strength of the Liquid Silicon Infiltrated (LSI) ceramic-matrix composite (CMC), C/C-SiC, were investigated in varying orientations relative to the 0°/90° woven carbon fibres. The ratio of bending to tensile strength was about 1.7-2 depending on the loading direction. The non-linear stress-strain behaviour under tensile load and the linear elastic behaviour under compression load were included in the finite element analysis (FEA) of bending behaviour. The bending failure of the CMC-material was modelled by Cohesive Zone Elements (CZE) accounting for the directional tensile strength and Work of Fracture (WOF). The WOF was determined by Single Edge Notched Bending (SENB) tests. Comparable results from FEA and bending test were achieved. It was demonstrated that the failure of C/C-SiC at room temperature may be described by a macroscopic fracture mechanical FE-approach. The presented approach could also be adapted for the design of CMC-components and structures.