Strain Distributions and Over-Stressed Volumes in Unidirectional Composites with Multiple Fiber Breaks

Abstract

A finite element technique was used for determining the strain distribution around fiber breaks in unidirectional composite monolayers subjected to tensile stress in the fiber direction. Various extents of damage, ranging from a single fiber break to ten adjacent fiber breaks, were considered. Both the fiber and the matrix were considered to be elastic. From the finite element results, the level of overloading in fibers around such damage and the volume of neighboring fibers subjected to overload were determined. To provide a detailed description of the stress distribution, this over-stressed volume was divided into sub-volumes corresponding to various strain levels and presented in the form of a histogram. Over-stressed volume histograms were generated for a variety of composite materials having various combinations of fiber volume fraction and matrix stiffness. In most cases, the stress concentration factor obtained from the finite element analysis was significantly greater than the corresponding value obtained by using the shear-lag model. The overstressed volume histograms are expected to be useful in the strength prediction of composite materials.