Finite element analysis model of the cumulative damage failure process in a continuous-fibre ceramic composite loaded in flexure

A finite element analysis (FEA) using macro-based input commands was used t o model the cumulative damage failure process of a continuous-fibre ceramic composite loaded in flexure. The modelling was predicated by the subject m aterial which exhibited asymmetric stress-strain response for uniform uniax ial monotonic tensile and compressive loading. The FEA model of the prismat ic rectangular flexural beam was composed of separately meshed fibre and ma trix elements loaded in four-point flexure. The cumulative damage process w as modelled using a macro-based input code combined with an element 'kill' command that was used to change the stiffnesses of those fibre and matrix e lements whose respective ultimate tensile strengths were exceeded by the re sulting tensile stresses. Matrix elements were allowed to support compressi ve stresses up to the ultimate compressive strength of the matrix material. However, unsupported fibre elements (i.e. those coincident with 'killed' m atrix elements) were not allowed to support compression. Even though the mo del did not explicitly include the behaviour of the interphase material, go od agreement between the FEA results and experimental test results was foun d for the subject three-dimensionally braided Nicalon (TM) fibre-reinforced beta -SiC matrix composite.