DIAMETRAL COMPRESSION TESTING OF METAL-MATRIX COMPOSITES

For the design and optimisation of advanced materials, the possibility of reliably testing very small amounts of material or laboratory scal e simple shape specimens is particularly interesting. To satisfy such requirements, this work presents a new procedure for mechanical testin g of metal matrix composites. The method is essentially a diametral co mpression of cylindrical specimens and represents an improvement of th e 'Brazilian' test. The mechanisms leading to fracture of composites h are been investigated via the mechanical behaviour of different metal matrix composites (A354-SiCp, A354-Al2O3 short fibres) and considerati on given to the role of the major parameters involved (both test and m aterial related). The results of the diametral compression test, in te rms of rupture strength have been compared with those of conventional tensile tests and characterisation of the microstructure via light and electron microscopy has been carried out. Evaluation of the results l ed to the conclusion that the failure of the materials is due to a ten sile mechanism, according to elasticity theory, and that under identic al testing conditions, for all the composites examined, the ratio of u ltimate tensile strength/rupture strength is constant. The method deve loped constitutes a useful and rapid tool for both the selection of ra w materials and the optimisation of metal matrix composite manufacturi ng processes. (C) 1994 The Institute for Materials.