Dynamic crack growth in particulate bimaterials having discrete and diffuse interfaces: Role of microstructure

Role of microstructure on interfacial crack growth in particulate bimaterials made of glass particle reinforced epoxy is examined experimentally. Two types of bimaterials, one with a discrete jump in mean filler particle size across the interface and the other with two intermixed particle sizes in the interfacial region, are studied. The choice of particle sizes used in bimaterials is based on a set of experiments in which particle size effects on fracture behavior of monolithic specimens with single particle size are established using optical interferometry and high-speed photography. A non-monotonic steady state stress intensity factor (K-Iss) variation with mean particle size is observed in the size range of 7-203 mu m for 10% volume fraction. Among the selected particles sizes, 35 mu m mean diameter is found to produce the highest K-Iss, Increasing or decreasing particle size results in measurable reduction in K-Iss of the composite. Based on this result, discrete and diffuse bimaterials made of 35 pm and 203 mu m diameter filler particles are studied. The K-Iss of the diffuse interface with intermixed particle sizes is bounded by the ones for monolithic configurations with single size particles. Further, K-Iss appears to vary linearly with the volume fraction of particle size having lower K-Iss in monolithic configurations. On the contrary, in case of a microstructurally discrete interface, the measured K-Iss is same as the one for the weaker half of the bimaterial. (c) 2005 Elsevier Ltd. All rights reserved.