ABSTRACT
The use of Metal Matrix Composites (MMC) is considered for applications in the hypervelocity vectors guidance domain. The guidance function have to be provided under extreme thermomechanical conditions but during a very short time. This paper deals with the determination of aluminium alloys based MMCs thermal properties and with their behavior under transient high fluxes.
Thermal diffusivity of Al-SiC composites for two matrix natures (X2080 and X7093) and different SiC/Al ratio have been determined. These measurements have been performed by using a method in which one face of a flat sample is exposed to a periodically modulated laser beam. The laser modulation shape was optimized so that multiple frequency measurement could be carried out during each test. Thermal diffusivity is identified by minimizing the differences between calculated and measured values for the phase shift between the incident flux and the resulting oscillations on the rear face temperature. Results show a diffusivity decrease when SiC fraction increases and an observable difference between the two composite families: diffusivity values being lower for X2080 matrix composites.
Transient heating behaviour of MMCs, involving ablation phenomena, have been studied using a flux controlled solar furnace. The fused metal was evacuated by a centrifugation process actuated by a pneumatic engine. Specimens weight loss and temperatures evolutions have been measured. It become apparent that X2080 matrix associated with a large amount of SiC particles delays the ablation phenomena.
