NUMERICAL MODELING OF THE MECHANICAL RESPONSE OF A CONTINUOUS FIBER CERAMIC COMPOSITE IN FLEXURE

摘要

A numerical model was implemented to predict the mechanical response in the non uniform stress state of flexure for a continuous fiber ceramic composite which exhibited non symmetric stress-strain response for uniform, uniaxial monotonic tensile and compressive loading. The finite element analysis (FEA) model of a prismatic, rectangular beam composed of separately meshed fiber and matrix elements was subjected to four-point flexural loading. A macro code combined with an element "kill" command was used to change the stiffnesses of elements whose statistically-distributed strengths were exceeded by the resulting stresses. Matrix elements were allowed to support unlimited compression. However, unsupported fiber elements (i.e., those coincident with "killed" matrix elements) were not allowed to support compression. Although the model does not directly incorporate the behavior of the interphase material, good agreement between the FEA results and experimental test results was found for a three-dimensionally braided Nicalon? fiber reinforced beta-SiC matrix composite.