The effect of varying the volume fraction of 650 mu m glass beads in a poly(vinyl butyral) matrix on the level of debonding in the particulate composites at a given applied tensile stress was investigated. Both clean beads and ones surface treated with the adhesion promoter 3-aminopropyltriethoxysilane were used. A model was developed to predict the observed behavior, based on Goodier's analytical solution for the stress concentration developed by a single sphere in an infinite matrix and the superposition of stress concentrations. By increasing the volume fraction of glass beads the average interparticle distance is decreased, leading to an increase of the overlap of the stress concentration fields surrounding the beads, thus causing debonding at a lower applied stress. The use of an adhesion promoter increased the maximum local stress required to cause debonding, but had no effect on the interparticle stress fields so the same trends, at higher applied stress, were observed. The model, although quite simple, showed good agreement with the experimental results for the dependence of the particle-matrix debonding behavior on the volume fraction of beads. (C) Koninklijke Brill NV, Leiden, 2011