The influence of interface and arrangement of inclusions on local stresses in composite materials

We studied a model composite material consisting of a thin epoxy plate (matrix) reinforced with stiff circular disks (inclusions) and subjected to a uniaxial tension. At each inclusion-matrix interface there is an interfacial layer, an interphase, which has uniform properties. The inclusions are arranged in the matrix at random but with no overlap. For comparison we also considered square and triangular periodic arrangements. We have studied elastic fields of such composites both experimentally, using a photoelasticity method, and numerically via a finite element method. We have found that random inclusion arrangements give higher stress concentrations than the periodic ones owing to stress localizations. The highest stress increase is in a compliant interface case, which also exhibits the highest scatter in stress magnitudes for different random arrangements al the same volume fraction. (C) 1997 Acta Metallurgica Inc.