Modelling the Bending Test Behaviour of Carbon Fibre Reinforced SiC by Finite Element Method

Liquid silicon infiltrated carbon fibre reinforced SiC, has shown to be a high-potential material for thermal protection systems. The tensile and bending behaviour of the ceramic-matrix composite, 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 to 2 depending on the loading direction. With the goal to understand this large difference finite element analyses (FEA) of the bending tests were performed. The different stress-strain behaviour of C/C-SiC under tensile and compression load were included in the FEA. Additionally 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. The presented approach could also be adapted for the design of C/C-SiC-components and structures.