A tensile strength model for unidirectional fiber-reinforced brittle matrix composite

A model for the ultimate tensile strength of unidirectional fiber-reinforced brittle matrix composite is presented. In the model, transverse matrix crack spacing and change in debonding length between the fiber and the matrix is continuously monitored with increasing applied load. A detailed approximate stress analysis, together with a Weibull failure statistics for fiber fracture, are used to determine the probability of fiber fracture and fiber fracture location in the composite. Results of the model are consistent with experimental data. It is suggested from the results that the strength and toughness of the composite are significantly influenced by the Weibull modulus of the fiber and the fiber/matrix interfacial shear stress. A higher fiber Weibull modulus results in a lower composite strength while a higher fiber/matrix interfacial shear stress results in a composite with higher strength but lower toughness. A moderate variation in matrix strength and fiber/matrix intefacial shear strength does not significantly affect the strength of the composite.