Shrinkage stresses in three-dimensional two-phase systems

Abstract

Stress fields, due to polymerization shrinkage of a matrix cast around a three-dimensional array of closely packed inclusions, were studied photoelastically. The composite model consisted of a group of spherical inclusions, made of unplasticized hot-setting epoxy resin and forming a body-centred cubic arrangement, around which a plasticized matrix was cast, so that control over the ratio of matrix modulus to inclusion modulus was possible.A theoretical approximation to the problem of stress distribution around a single inclusion was also attempted and subsequently found to be in fair agreement with experimental results.With closely packed inclusions the stress distribution was studied for different degrees of packing and matrix plastification. From these studies further conclusions can be drawn, confirming the validity of the qualitative results stated for a single inclusion.