Influence of Elastic Mismatch and Nature of Interfacial Bonding on Toughness of Particulate Composites

Abstract

<p>This work involves the study of crack-particle interaction in model brittle particulate composites where,</p> <p>i) the interfacial bonding strength between second phase and matrix was continuously varied (glass - partly oxidized Ni system) and</p> <p>ii) the presence and absence of elastic mismatch between second phase and matrix which gives rise to stress concentration around the particle was monitored. An ultrasonic fracture surface modulation technique was used which imprints the details of local crack-particle interaction on fracture surface.</p> <p>The important results of this study are:</p> <p>i) Both the interfacial strength and elastic mismatch important roles in improving the toughness of a particulate composite; optimum bond strength alone; without consideration of elastic mismatch may not improve toughness of a composite be a significant amount.</p> <p>ii) For optimum toughening, second phase particles with a high intrinsic toughness which are well-bonded to the matrix and whose elastic moduli are equal to or less than that of matrix should be used.</p> <p>iii) Due to the presence of elastic stress concentration, for second phase particles whose elastic moduli exceeds that of the matrix, a rather weak interfacial bonding is preferred to a strong interfacial bonding for effective crack particle interaction which will improve the toughness of a composite.</p> <p>In summary, this work provides some guidelines for choice of proper second phase particles and matrix in the design of brittle particulate composites for optimum toughness.</p>