Influence of voids on the stress distribution and deformation behaviour ofepoxies under uniaxial deformation

A zero-order model is presented, which allows calculation of the stress dis tribution in porous epoxies by taking into account the interaction between randomly distributed voids. These results demonstrate that the mean value o f the stress concentration factor increases with the volume fraction of voi ds. This leads to a decrease in sample yield strength. However, the generat ion of a porous morphology also creates a considerable number of regions wh ere the stress is completely released. The theoretical predictions are in g ood agreement with experimental results obtained with macroporous epoxies, which were prepared based on the chemically induced phase separation techni que, and tested under uniaxial compression. (C) 1998 Kluwer Academic Publis hers.