Crack-Particle Interactions in Brittle Composites

Abstract

<p>A study was made of the fracture in a model composite containing nickel spheres in a glass matrix. The macroscopic fracture characteristics of the system were determined by fracture surface energy, strength and elastic modulus measurements. The microstructures of the composites were defined carefully using quantitative microscopy and the fracture processes were studied using fractographic techniques. In particular, the technique of ultrasonic fractography was used to study the crack-particle interactions in detail.</p> <p>It was found that for a non-bonded S glass-nicker system, the crack shape changes were similar to those observed for a glass-pore system. Theoretical models were used to explain the crack shape variations and their effect on properties. These models were based on the interaction of the stress field of the crack and the particles by local crack blunting and image stresses. Good agreement was obtained between theoretical predictions and experimental measurements of crack shape at breakaway and the fracture surface energy variations.</p>