CERAMIC-MATRIX COMPOSITES FOR THERMOSTRUC TURAL APPLICATIONS

To be able to satisfy the materials requirements of the aerospace sect or, mainly mass reduction and highest working temperature (T), some ce ramic matrix composites have been developed at ONERA since the early 8 0's: glass-ceramics (T < 1200 degrees C), oxides as mullite and alumin a (T < 1500 degrees C), silicon carbide (T < 1700 degrees C) which are principally reinforced with commercial SiC fibres exhibiting today a thermostability of about 1400 degrees C. To improve matrix densificati on and reduce cost, the specific properties of liquid ceramic precurso rs have been taken into account to develop new processing routes: Sol- Gel technique using alkoxides for oxides and organosilicon polymers as polyvinysilane for SIG. The mechanical behaviour studies have reveale d that the composites durability under hot air is governed by the oxid ation resistance of the fiber-matrix carbon interphase which is necess ary to guarantee the damage tolerant behaviour. Efforts would be now f ocused on the development of lamellar interphases with low toughness a nd better oxidation resistance.