Statistical strength of unidirectional composites and the effect of the interfacial shear strength

A microscopic statistical analysis of the longitudinal tensile failure of unidirectionally fibre-reinforced composites has been performed. On the basis of the random critical-core probability model, in conjunction with the results of a stress-concentration analysis with interfacial damage between fibres and matrix, the strength-distribution function and failure criterion for composites with the effect of the interfacial shear strength are derived and the relationship between the tensile strength and interfacial shear strength of composites is obtained. The present results provide an important theoretical basis for the optimum design of composite microstructure. The correctness and reasonableness of the present methods and results are validated by existing experiments. Finally, the question of optimum interfacial bonding is discussed quantitatively. (C) 1996 Elsevier Science Limited