Stress concentrations in composites with interface sliding, matrix stiffness and uneven fiber spacing using shear lag theory

The stress concentrations near a single fiber break in a unidirectionally r einforced fiber composite are investigated using a shear lag theory within the framework of finite elements. A model for uniformly spaced, well bonded fibers embedded in a matrix that cannot carry axial loads that was formula ted previously is first introduced. The solution of this problem involves F ourier transforms and requires only a two-dimensional numerical integration . The work described in the current paper characterizes the stress concentr ations around a single fiber break in the presence of fiber/matrix interfac e sliding, axial matrix stiffness and uneven fiber spacing. Due to the intr oduction of these complicating factors, the model no longer lends itself to the simple Fourier transformation solution method. For the case of interfa ce sliding a new method is developed to handle sliding in any shear lag sys tem. For the cases of axial matrix stiffness and uneven fiber spacing a fin ite element code specifically written for this problem is used to determine the fiber stresses. The results are discussed in the context of global ver sus local load sharing, and the effects on composite failure. (C) 1999 Else vier Science Ltd. All rights reserved.