MEASUREMENT OF INTERFACE STRENGTH IN AL SIC PARTICULATE COMPOSITES/

Fracture in particulate-reinforced metal-matrix composites is initiate d by particulate cracking and interface decohesion, and crack propagat ion occurs through the matrix, particulate and interface. A 'critical stress partition' model is described which considers the proportions o f matrix, particulate and interface for which the fracture stress is e xceeded. Tensile tests and microhardness measurements are reported for SIC/Al metal-matrix composites having particulate volume fractions of 0-20%. Measurements of the fractions of cracked and interface-debonde d particulate before and after final fracture are combined with the fr acture model to calculate the interface strength, sigma(int)'. The val ues of sigma(int)' obtained are 469 MPa for uncoated SiC particulate a nd 438 MPa for particulate coated with a thin layer of Al2O3 to preven t interface reaction. The tensile results indicate that the weaker int erfaces promote interface debonding and increase percent elongation.