セラミックス基繊維強化複合材料の界面接触モデルによるＦＥＭ定式化と強度シミュレーション

Abstract

A new finite element model for the damage analysis of fiber-reinforced ceramics matrix composites is proposed, in which the effect of the friction of interfacial sliding after debonding between the fiber and matrix are taken into account. It is assumed that three interfacial contact states, i.e. (1) interfacial bonding, (2) interfacial sliding, and (3) interfacial sliding with fiber breakage, exist in the composite during loading. Then, stiffness matrix of each interfacial contact state is newly formulated. It was found that the number of conditional unknown displacements was always equal to that of unknown loads. Therefore, the computation can be carried out without any change in size of the structure stiffness matrix. The calculated stress distribution was characterized by that the stress recovery region along a broken fiber is composed of two different stress distributions corresponding to the bonding and debonding regions. Monte-Carlo method was taken into the proposed finite element model, and stress-strain diagrams of a carbon-coated SiC fiber reinforced SiC matrix composite were predicted by superposition method. The results show that the average strength gradually decreases with an increase in the number of fibers; the coefficient of variation decreases. Finally, the simulated stress-strain diagram was compared with probabilistic models proposed by Phoenix-Raj and Goda et al.