• PDF / 859,654 Bytes
• 5 Pages / 612 x 792 pts (letter) Page_size
• 68 Downloads / 294 Views

DOWNLOAD

REPORT

---

IN this

investigation thermal expansion measurem e n t s w e r e made on c o m p o s i t e s of s i l i c o n c a r b i d e coated b o r o n f i b e r s (BORSIC) a n d two a l u m i n u m a l l o y m a t r i c e s , 1100 and 2024. M e a s u r e m e n t s were made c o a x i a l l y with and at 90 deg to the f i b e r s for v a r i o u s v o l u m e f r a c t i o n f i b e r s and at v a r i o u s a n g l e s to the f i b e r s for 50 pct v o l u m e f r a c t i o n f i b e r s . The two m a t r i x a l l o y s were c h o s e n to r e p r e s e n t a soft a l u m i n u m a l l o y 1100 and a r e l a t i v e l y h a r d a l u m i n u m alloy, 2024, b e c a u s e it was r e c o g n i z e d that p l a s t i c d e f o r m a t i o n m a y take p l a c e in the m a t r i x which has a m e a n e x p a n s i o n c o e f f i c i e n t of 24 • 10 -e p e r ~ c o m p a r e d to the 4.6 to 4.9 x 10 -e p e r ~ of the b o r o n f l "~ It was also r e c o g n i z e d that the m a t e r i a l does not have a t r u e h o m o g e n e o u s e x p a n s i o n c o e f f i c i e n t ; but, due to the l a r g e i n t e r e s t in the t h e r m a l p r o p e r t i e s of this c o m p o s i t e s y s t e m , the e m p i r i c a l v a l u e s a r e r e p o r t e d h e r e i n and c o m p a r e d to certain theoretical composite thermal expansion pred i c t i o n s in the l i t e r a t u r e . *-a T h e s e p r e d i c t i o n s of 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 s a r e g e n e r a l l y b a s e d on the a s s u m p t i o n of wholly e l a s t i c b e h a v i o r . EXPERIMENTAL PROCEDURE C o m p o s i t e s w e r e h o t - p r e s s d i f f u s i o n bonded at 20 ~ to 40~ below t h e i r m a t r i x s o l i d u s t e m p e r a t u r e s and 5000 p s i f r o m p l a s m a - s p r a y e d m o n o l a y e r t a p e s . 9 A slow cool was used to m i n i m i z e r e s i d u a l s t r e s s e s and y i e l d e d an " a n n e a l e d " s t r u c t u r e . The t h e r m a l e x p a n s i o n of the c o m p o s i t e s p e c i m e n s was m e a s u r e d by m e a n s of q u a r t z tube d i l a t o m e t e r . The s a m p l e c o n t a c t e d a s o l i d q u a r t z plug i n s i d e of a q u a r t z tube. A q u a r t z p u s h rod was i n s e r t e d into the tube and c o n t a c t e d the o t h e r end of the c o m p o s i t e s p e c i m e n . As the s p e c i m e n expanded, the q u a r t z rod was p u s h e d out of the tube d i s p l a c i n g the c o r e of a l i n e a r v a r i a b l e d i f f e r e n t i a l t r a n s f o r m e r (LVDT). A c h r o m e l - a l u m e l t h e r m o c o u p l e was p o s i t i o n e d v e r y n e a r to, but not touching, the s p e c i m e n . The d i l a t o m e t e r was then p l a c e d into a r e s i s t a n c e f u r n a c e KENNETH G. KREIDER and VALENTINO M. PATARINI are Program Manager-CompositeMaterials and Research Scientist, respectively, United Aircraft ResearchLaboratories, East Hartford, Conn. Manuscript submitted April 6, 1970. METALLURGICALTRANSACTIONS