A comparison between creep of laminated aluminum and the transverse creep behavior of a unidirectional boron-aluminum co
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r e c t i o n of the a p p l i e d s t r e s s v a r i e d f r o m the d i r e c t i o n of r e i n f o r c e m e n t , the c r e e p r e s i s t a n c e of the c o m p o s i t e d e c r e a s e d d r a m a t i c a l l y , and it w a s f u r t h e r shown that c r o s s - p l i e d c o m p o s i t e s w e r e s u p e r i o r to u n i d i r e c t i o n a l c o m p o s i t e s l o a d e d off the longitudinal axis. E r i c k s e n 8 h a s found that the c r e e p r a t e s of t r a n s versely loaded boron-aluminum composites are somewhat l o w e r t h a n the c r e e p r a t e s f o r the u n r e i n f o r c e d m a t r i x at the s a m e s t r e s s at 300 K. T h i s s u g g e s t s that the f i l a m e n t s m a y have s o m e s t r e n g t h e n i n g effect on the m a t r i x f o r t h e s e c o n d i t i o n s . B r e i n a n and K r e i d e r ~ gave r e s u l t s for t r a n s v e r s e c r e e p of c o m p o s i t e s c o n t a i n i n g 50 vol pct b o r o n o r B o r s i c | f i l a m e n t s in a v a r i e t y of a l u m i n u m m a t r i x a l l o y s , s u c h a s 6061 and 2024. T h e y r e p o r t e d that the c r e e p r a t e of the t r a n s v e r s e l y l o a d e d c o m p o s i t e i s s t r o n g l y d e p e n d e n t on the condition of h e a t t r e a t m e n t of the m a t r i x , and c r e e p r a t e s in the c o m p o s i t e s w e r e v e r y s i m i l a r to the c r e e p r a t e s of the u n r e i n f o r c e d m a t r i x ; d e p e n d i n g on the m a t r i x a l l o y and h e a t t r e a t m e n t , the c o m p o s i t e m a y be e i t h e r w e a k e r o r s t r o n g e r than the m a t r i x a l o n e . T h e s t r e n g t h of the c o m p o s i t e s r e l a t i v e to the m a t r i x was a t t r i b u t e d in p a r t to l o n g i t u d i n a l s p l i t t i n g of the f i l a m e n t s in the c o m p o s i t e . T h e s e r e s u l t s i n d i c a t e that the l o n g i t u d i n a l c r e e p b e h a v i o r of t h e s e c o m p o s i t e m a t e r i a l s i s g o v e r n e d p r i m a r i l y by t h e b o r o n f i l a m e n t s , w h i l e the t r a n s v e r s e c r e e p b e h a v i o r i s m o r e like that of the m a t r i x . C u r r e n t p h e n o m e n o l o g i c a l t h e o r i e s f o r c r e e p in p u r e m e t a l s and a l l o y s i m p l y s p e c i f i c r e l a t i o n s h i p s b e t w e e n s t r e s s , t e m p e r a t u r e , and the c r e e p r a t e . If c r e e p of the m a t r i x c o n t r o l s the t r a n s v e r s e c r e e p of the c o m p o s i t e m a t e r i a l , one would e x p e c t to s e e s i m i l a r r e l a t i o n s h i p s a p p l y to the c o m p o s i t e m a t e r i a l . T h e r e a r e , of c o u r s e , m a n y p o s s i b l e c o m p l i c a t i n g f a c t o r s which m a y l e a d to b e h a v i o r unique to the c o m p o s i t e . R e s u l t s a r e p r e s e n t e d h e r e which i l l u s t r a t e the r e l a t i o n s h i p b e tween the s t r e s s and t e m p e r a t u r e d e p e n d e n c e of c r e e p f o r a m a
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