IMPACT AND CHEVRON-NOTCH FRACTURE-TOUGHNESS TESTING OF PARTICULATE METAL-MATRIX COMPOSITES

Reliable mechanical testing procedures for particulate metal matrix composites are essential for both alloy development and component design. The measurement of toughness properties in these materials presents particular difficulties. In this paper, Charpy impact and chevron notch fracture toughness testing of an Al 2124-17%SiC alloy ale described. Although impact testing is a relatively simple technique for grading alloy toughness, it has not been widely used for metal matrix composites. Here, the effects of notch type and specimen thickness are examined and recommendations are made regarding the optimum testing procedure. Conventional fracture toughness tests using prefatigued specimens are difficult to apply to particulate metal matrix composites because residual stresses give rise to bowed crack fronts. The short bar chevron notch test, in which a crack is initiated at the apex of the machined notch and the toughness is evaluated after the crack has grown to a critical length, is therefore particularly suitable for these materials. (C) 1994 The Institute of Materials.