一方向性繊維強化複合材料における破断繊維の隣接繊維におよぼす静的応力集中効果

抄録

The static stress concentration in the fibres adjacent to broken fibres, the stress distribution along the fibre axis in the broken and intact fibres and shear stresses between broken and intact fibres in elastic fibre-metal matrix composites were calculated using a two-dimensional model applying the shear lag analysis. The effects of plastic deformation of matrix and those of interfacial debonding on the stress concentration and stress distribution were quantitatively estimated. The following points were clarified in a qunatitative manner. (1) When the interfacial bonding strength is lower than the yield stress of the matrix in shear, the interfacial debonding occurs, when applied stress becomes higher than the threshold stress for the interfacial debonding to arise. After the interfacial debonding occurs, the length of a region showing debonding increases rapidly with increasing stress level. The stress concentration in the fibres adjacent to broken fibres decreases rapidly due to the interfacial debonding. (2) When the interfacial bonding strength is much higher than the yield stress of the martix in shear, the matrix yields in shear, when applied stress becomes higher than the threshold stress for shear yielding of the matrix to arise. After the shear yielding of the matrix, the stress concentration in intact fibres decreases with increasing stress level. When the yield stress, the shear modulus and the strain hardening coefficient of the matrix are low, the stress concentration factor in intact fibres decreases rapidly with increasing stress level. (3) The interfacial debonding and shear yielding of the matrix in shear act to reduce the stress concentration factors in the intact fibres, which, on the other hand, causes to increase the critical length of the fibre necessary for the reinforcement. Thus the efficiency of reinforcement is reduced, especially by the interfacial debonding.