NASA Technical Memorandum 101414 Noninteractive Macroscopic Reliability Model for Ceramic Matrix Composites

A macroscop ic n o n i n t e r a c t i v e r e l i a b i l i t y model for ceramic m a t r i x composi tes i s p resented . The model i s m u l t i a x i a l and a p p l i c a b l e t o composi tes t h a t can be c h a r a c t e r i z e d as o r t h o t r o p i c . T e n s o r i a l i n v a r i a n t t h e o r y i s used t o c r e a t e an i n t e g r i t y b a s i s w i t h i n v a r i a n t s t h a t cor respond t o p h y s i c a l mechanisms r e l a t e d t o f r a c t u r e . T h i s i n t e g r i t y b a s i s i s then used t o conN s t r u c t a f a i l u r e f u n c t i o n p e r u n i t volume (or a rea ) o f ~n m a t e r i a l . I t i s assumed t h a t t he o v e r a l l s t r e n g t h o f I t h e compos i te i s governed by weakest l i n k t h e o r y . T h i s l eads t o a We ibu l l t y p e model s i m i l a r i n n a t u r e t o the p r i n c i p l e o f independent a c t i o n (PIA) model for i s o t r o p i c m o n o l i t h i c ceramics . An exper imen ta l program to o b t a i n model parameters i s b r i e f l y d i scussed . I n add i t i o n , q u a l i t a t i v e f e a t u r e s o f t h e model a r e i l l u s t r a t e d by p r e s e n t i n g r e l i a b i l i t y s u r f a c e s f o r v a r i o u s model parameters . 4