FRACTURE-TOUGHNESS MEASUREMENTS AND FAILURE MECHANISMS OF METAL-MATRIX COMPOSITES

This paper compares the fracture toughness values obtained from two di fferent specimen geometries, i.e. pre-cracked compact tension and chev ron-notched short rod. The former is in widespread use, however, the l atter has significant advantages in that no pre-cracking is required r esulting in more economical use of material and reduced machining. Fou r 6061-aluminium-matrix composites reinforced with discontinuous alumi na particles were investigated. Good agreement in fracture toughness v alues from the two specimen geometries was obtained for all the materi als and all the heat treatments examined. Detailed analyses of the fra cture surfaces were used to identify the fracture mechanisms. The effe cts of specimen geometry, volume fraction of reinforcement and ageing treatment on fracture toughness are discussed.