Local stress concentration and the prediction of tensile failure in unidirectional composites

The aim of this paper is to present a new representation of the tensile failure of a composite material which accounts for the normal stress supported by the matrix and allows a stduy of the influence of constituent material properties and fiber volume fraction on the sterss-concentration factors. This is done by micromechanical analysis which allows the stress and strain in the fibers and the matrix to be related to the applied stress or strain on the composite. Stress-concentration factors are calculated in the composite transverse section and are found to be smaller than previously published analytical solutions. The difference is essentially due to the normal stress supported by the matrix which is neglected by the shear-lag analysis but is taken into account in our model. The tensile strength is calculated firstly by numerical simulations and secondly by Batdorf's methodology which addresses the formation and propagation of fiber fractures. Comparisons with experimental measures are satisfactory. (Material in example cited: continuous fiber glass/epoxy composites.)