Si-Ti-C-O系セラミックス繊維強化アルミニウム複合材の混合モード荷重下における破壊靱性と疲労き裂進展特性

概要

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Fracture toughness for crack along a long fiber and the fatigue crack growth rate in the same direction were experimentally examined in Si-Ti-C-O fiber-reinforced aluminum composite under mixed-mode loading of modes I and II. The fracture curve under mixed-mode loading was expressed by the equation (K_I/12.0)^2+(K_II/15.5)^2=1, where modes I and II fracture toughnesses are 12.0 and 15.5 Mpa・m^1/2. In this case the fracture toughness of the composite material is not described by any fracture criteria proposed for common homogeneous materials. It, however, is best interpreted by the strain energy release rate criterion among these criteria. The scanning electron microscope observations showed that the crack extended through the aluminum matrix along the fiber-arranged direction under any mixed-mode loading conditions. Such a fracture mode might induce a characteristic fracture which is not dominated well by the common criteria. A fatigue crack under mixed-mode loading also extends through the aluminum matrix, leaving a striation, and its growth rate is governed well by the effective equivalent stress intensity factor range evaluated on the basis of the concept of strain energy release rate.
1994-09-25