Stress concentrations caused by fiber failure in two-dimensional composites

Abstract

In the process of fracture of fiber-reinforced composites, the stress concentrations caused by the redistribution of stress from a failed fiber to its intact adjacent neighboring fibers play a substantial role, as they determine the overall failure pattern of the composites. In the present article we propose a new model for the stress concentration factors (SCFs) in two-dimensional unidirectional composites. This model is based on an earlier shear-lag scheme which is here modified in several respects: a new shear-lag constant β N (proposed by Nayfeh) is included (which replaces the classical shear-lag constant of Cox, β C), and the effects of fiber/matrix debonding and fiber/matrix interfacial friction are incorporated. We find that the proposed model is in good agreement with recently published Raman spectroscopy results. When the fibers are in close contact, the SCF is found to possess a maximum value of 1.33, identical with the classical result of Hedgepeth and Van Dyke. However, unlike the scheme of Hedgepeth and Van Dyke, the SCF decreases with increasing interfiber distance, similar to more recent models, but in closer agreement than these models with the micro-Raman spectroscopy data.