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 scale simple shape specimens is particularly interesting. To satisfy such requirements, this work presents a new procedure for mechanical testing of metal matrix composites. The method is essentially a diametral compression of cylindrical specimens and represents an improvement of the 'Brazilian' test. The mechanisms leading to fracture of composites hare been investigated via the mechanical behaviour of different metal matrix composites (A354-SiCp, A354-Al2O3 short fibres) and consideration given to the role of the major parameters involved (both test and material related). The results of the diametral compression test, in terms 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 led to the conclusion that the failure of the materials is due to a tensile mechanism, according to elasticity theory, and that under identical testing conditions, for all the composites examined, the ratio of ultimate tensile strength/rupture strength is constant. The method developed constitutes a useful and rapid tool for both the selection of raw materials and the optimisation of metal matrix composite manufacturing processes.