FABRICATION AND CHARACTERIZATION OF CERAMIC MATRIX-CERAMIC WHISKER COMPOSITES WITH RAN- DOM ORIENTATION OF THE WHISKERS

FABRICATION AND CHARACTERIZATION OF CERAMIC MATRIX- SIC WHISKER COMPOSITES BY PRESSURELESS SINTERING FOR ADVANCED HEAT ENGINES IS PLANNED. DENSIFICATION OF WHISKER-REINFORCED COMPOSITES WITH HIGH LOADING OF WHISKER CONETNT HAS BEEN ACHIEVED TO DATE ONLY BY HOT PRESSING. NOVEL METHODS ARE PROJECTED, BASED ON PRIOR WORK, WHICH PERMIT THE FABRICATION OF COM- POSITES BY PRESSURELESS SINTERING SO THAT NEAR-NET- SHAPE ARTICLES CAN BE FABRICATED REQUIRING LITTLE OR NO POST-FABRICATION MACHINING. ALSO, THE CONVENTIONAL FORMING AND DENSIFYING METHODS INVARIABLY LEAD TO PREFERRED ORIENTATION OF WHISKERS IN THE FINAL OBJECT LEADING TO ORIENTATION-DEPENDENT PROPERTIES. SPECIF- ICALLY, IF THE CRACK PLANE IS PARALLEL TO THE WHSKERS, THE TOUGHNESS AND THE STRENGTH ARE LOW. THIS IS GEN- ERALLY UNDESIRABLE. A NOVEL POWDER PROCESSING METHOD IS PLANNED WHICH WILL PERMIT A RANDOM ORIENTA- TION OF THE WHISKERS IN THE BODY SO THAT THE RESULTING ARTICLE WILL HAVE NEAR ISOTROPIC PROPERTIES. WORK IS PLANNED ON DETERMINING FRACTURE TOUGHNESS AND STRENGTH AS A FUNCTION OF ORIENTATION AND ON COR- RELATING THE PROPERTIES TO THE DEGREE OF TEXTURE.