Thermal cycling-induced deformation of fibrous composites with particular reference to the tungsten-copper system
- PDF / 1,545,445 Bytes
- 8 Pages / 613 x 788.28 pts Page_size
- 92 Downloads / 214 Views
F
IBER-reinforced metal- matrix composites are c o n s i d e r e d a s p o t e n t i a l s t r u c t u r a l m a t e r i a l s f o r hight e m p e r a t u r e a p p l i c a t i o n s . In p a r t i c u l a r , i n - s i t u c o m p o s i t e s p r o d u c e d by d i r e c t i o n a l s o l i d i f i c a t i o n of n i c k e l o r c o b a l t - b a s e d e u t e c t i c s and a r t i f i c i a l f i l a m e n t a r y c o m p o s i t e s with s u p e r a l l o y m a t r i c e s and r e f r a c t o r y - w i r e r e i n f o r c e m e n t s show g r e a t a t t r a c t i v e n e s s for u s e in a d v a n c e d g a s - t u r b i n e c o m p o n e n t s , b e c a u s e of t h e i r e x c e l l e n t e l e v a t e d - t e m p e r a t u r e t e n s i l e and s t r e s s - r u p t u r e s t r e n g t h s and i m p a c t r e s i s t a n c e . / ~ On the o t h e r hand, a s e r i o u s p r o b l e m that might r e s t r i c t the a p p l i c a b i l i t y of such m a t e r i a l s h a s b e e n r e c o g n i z e d , n a m e l y , the g e n e r a t i o n of t h e r m a l s t r e s s e s r e s u l t i n g f r o m the d i f f e r e n c e in t h e r m a l e x p a n s i o n c o e f f i c i e n t s of c o m p o s i t e c o n s t i t u e n t s , and i t s effect on the s t r u c t u r a l i n t e g r i t y and s t r e n g t h of c o m p o s i t e s e s p e c i a l l y under c o n d i t i o n s of e l e v a t e d t e m p e r a t u r e c y c l i n g . In fact, for i n s t a n c e , a i r c r a f t g a s t u r b i n e components usually experience multiple thermal c y c l e s b e t w e e n a m b i e n t t e m p e r a t u r e and e l e v a t e d t e m p e r a t u r e s t h r o u g h the i n t e r m i t t e n t o p e r a t i o n of t u r b o j e t engines; the p r o b l e m is thus c r i t i c a l for s u c h service. R e c e n t l y , s o m e i n v e s t i g a t o r s have done e x p e r i m e n t s on t h e r m a l c y c l i n g of s e v e r a l d i f f e r e n t m a t e r i a l s in t h i s c l a s s and have o b s e r v e d t h o s e t y p e s of i n t e r n a l d a m a g e which a r e : i) f r a g m e n t a t i o n of the r e i n f o r c i n g p h a s e by m u l t i p l e c r a c k i n g , 4"~ ii) p l a s t i c t e n s i o n - c o m p r e s s i o n fatigue and r e s u l t i n g f a i l u r e of the m a t r i x , 4"~ iii) d e c r e a s e in the effective i n t e r r a c i a l bond s t r e n g t h o r d e c o h e s i o n at the p h a s e i n t e r f a c e , 6'~ and iv) m o r p h o l o g i c a l c h a n g e s of the r e i n f o r c i n g p h a s e due to p h y s i c o c h e m i c a l r e a c t i o n s . % 9,1~ A l l of t h e s e t y p e s of S. YODA, K. WAKASHIMA,and S. UMEKAWAare Graduate Student, Research Associate, and Professor, respectively, Research Laboratory of Precision Machinery and Electronics, Tokyo Institute of Technology, Yokohama 227, Japan. NOBUYA KURIHARA, formerly Graduate Student, is now with Nissan Automobile Co., Ltd., 6-1 Daikoku-cho, Tsurumi-ku, Yokohama 230, Japan. Mmluscript submitted March 23, 1977. METALLUR
Data Loading...
