Correlation of uniaxial yielding and substructure in aluminum-stainless steel composites
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H E m e c h a n i c a l b e h a v i o r of continuous fiber r e i n f o r c e d composite m a t e r i a l s c o n s i s t i n g of a m e t a l l i c m a t r i x and fiber has r e c e i v e d extensive a t t e n t i o n in r e c e n t y e a r s . ~ A m a j o r i t y of the s t u d i e s a r e c o n c e r n e d with the t h e o r e t i c a l t r e a t m e n t of m i c r o m e c h a n i c a l b e h a v i o r ; an e x t e n s i v e l i t e r a t u r e is available.2" 2s Gene r a l l y , these a n a l y s e s a r e b a s e d on the s o - c a l l e d " r u l e of m i x t u r e s " , or on p e r t u r b a t i o n s to this rule as a function of c o m p o s i t e v a r i a b l e s (residual s t r e s s e s , P o i s s o n ' s r a t i o d i f f e r e n c e s , f i b e r g e o m e t r y , bonding). To date, the validity of the a s s u m p t i o n s n e c e s s a r y in the m i c r o m e c h a n i c a l m o d e l s lacks a c o m p l e t e e x p e r i mental verification. Almost all experimental investigations have been d i r e c t e d at the m e a s u r e m e n t of e l a s t i c moduli and u l t i m a t e t e n s i l e s t r e n g t h s , or at the i n v e s t i g a t i o n of bonding p h e n o m e n a . ~6-21 T h e s e r e s u l t s have some a p p l i c a b i l i t y in v e r i f y i n g t h e o r e t i c a l a s s u m p t i o n s , and in d e m o n s t r a t i n g a d v a n t a g e s and l i m i t a t i o n s of composite m a t e r i a l s . However, the d e t a i l e d u n d e r s t a n d i n g of m i c r o 22 and m a c r o y i e l d i9 n g 1 9 n e c e s s a r y to validate m i c r o m e c h a n i c a l m o d e l s is l i m i t e d . C h e s k i s and Hecke123'24 have c o n f i r m e d the a p p l i c a b i l i t y of the rule of m i x t u r e s and the a b s e n c e of complex or l o n g - r a n g e i n t e r a c t i o n between m a t r i x and w i r e , p r o vided the load is a p p l i e d in the d i r e c t i o n of r e i n f o r c e m e n t and account i s taken of any r e s i d u a l s t r e s s e s p r e s e n t , u s i n g in situ X - r a y diffraction m e a s u r e m e n t s . In p a r t i c u l a r , the p h e n o m e n o n of m i c r o y i e l d i n g , which has b e e n a m p l y d e m o n s t r a t e d for single phase m a t e r i a l s and some a l l o y s , 26-29 r e q u i r e s f u r t h e r i n v e s tigation .22 M. R. PINNEL and A. LAWLEYare former Graduate Student and Head of the Department of Materials Engineering,respectively, Drexel University, Philadelphia, Pa. M. R. PINNEL is currently a member of the Technical Staff, Bell Telephone Laboratories, Columbus, Ohio. Manuscript submitted August 7, 1969. METALLURGICALTRANSACTIONS
The a i m of this r e s e a r c h is to c h a r a c t e r i z e the m i c r o y i e l d i n g and m a c r o y i e l d i n g b e h a v i o r of a typical continuous fiber m e t a l - m a t r i x c o m p o s i t e u n d e r both u n i a x i a l t e n s i l e and c o m p r e s s i v e loading. The m e c h a n i c a l b e h a v i o r is c o r r e l a t e d with the development of th
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