The effect of thermal cycling on the mechanical properties of various aluminum alloys reinforced with unidirectional bor
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b e t w e e n r o o m t e m p e r a t u r e and 588 K, 638 K, and 698 K and the r o o m t e m p e r a t u r e m e c h a n i c a l p r o p e r t i e s of each alloy were obtained after e x p o s u r e to 6000 t e m perature cycles.
E X P E R I M E N T A L TECHNIQUES Test Material The t e s t m a t e r i a l was f a b r i c a t e d by the A m e r c o m C o r p o r a t i o n u s i n g a p r o p r i e t a r y diffusion b o n d i n g t e c h nique. In g e n e r a l , the p r o c e s s c o n s i s t e d of applying a l a r g e p r e s s u r e to f o i l - f i l a m e n t a r r a y s at a t e m p e r a t u r e of about 773 K. The o r g a n i c b i n d e r which was used to m a i n t a i n the i n t e g r i t y of the o r i g i n a l m a t e r i a l was b u r n t off d u r i n g the diffusion b o n d i n g o p e r a t i o n . After f a b r i c a t i o n , the m a t e r i a l was cooled in a i r b y p l a c i n g the c o m p o s i t e panel on a l a r g e a l u m i n u m heat sink. T h r e e r e i n f o r c e d a l u m i n u m alloys, 1100, 2024, and 6061, w e r e f a b r i c a t e d , each c o n t a i n i n g a n o m i n a l 50 vol. pct, 1.42 x 10 -4 m d i a m b o r o n f i b e r s . Inspection of s o m e of the f i g u r e s p r e s e n t e d here indicated that f i b e r s that approached this d i a m e t e r w e r e p r e s e n t in s o m e of the s p e c i m e n s . However, m e a s u r e m e n t s t a k e n with a m i c r o m e t e r f r o m 50 f i b e r s e x t r a c t e d f r o m one s p e c i m e n r e s u l t e d in a c a l c u l a t e d m e a n d i a m e t e r of 1.35 x 10 -4 m. The v o l u m e f r a c t i o n of r e i n f o r c e m e n t in each s p e c i m e n was c a l c u l a t e d by counting the total n u m b e r of f i b e r s in each s p e c i m e n u s i n g an optical m i c r o scope and m u l t i p l y i n g the r e s u l t b y the a r e a of one f i b e r c a l c u l a t e d u s i n g the m e a s u r e d m e a n d i a m e t e r noted above. Using this method, the m e a n r e i n f o r c e m e n t c o n tent of the s p e c i m e n was computed to be about 44 vol. pct. As shown s c h e m a t i c a l l y in Fig. 1, the d i m e n s i o n s of each 3.048 x 10 -1 m s q u a r e p a n e l were sufficient to allow the p r e p a r a t i o n of 20 l o n g i t u d i n a l s p e c i m e n s , 12 t r a n s v e r s e s p e c i m e n s and 8 s h e a r s p e c i m e n s . These VOLUME 6A, JANUARY 1975-129
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