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p a r t 11 an a n a l y s i s for calculating the deformation of eutectic c o m p o s i t e s during t e m p e r a t u r e changes was derived. That a n a l y s i s is d i r e c t e d p r i n c i p a l l y toward the p r o b l e m of t h e r m a l - c y c l i n g damage with or without applied loadings. E x p e r i m e n t a l confirmation of the t h e o r y through m e a s u r e m e n t s of cycling damage is difficult, however. P r e s e n t l y the modes of deformation d u r ing cycling damage have not been d e t e r m i n e d positively, wide s c a t t e r e x i s t s in the a v a i l a b l e data, and m e a s u r e ments of internal s t r e s s e s a r e not c u r r e n t l y p o s s i b l e . As a r e s u l t , meaningful quantitative c o m p a r i s o n s of p r e d i c t i o n s and r e s u l t s of t h e r m a l cycling e x p e r i m e n t s cannot now be made. Fortunately, m e a s u r e m e n t s of the composite coefficient of t h e r m a l expansion can be used as a d i r e c t t e s t of the a n a l y t i c a l p r e d i c t i o n s . DeSilva and Chadwick z m e a s u r e d contraction of Cu-W and F e - B c o m p o s i t e s during cooling to v e r i f y t h e i r approach to t h e r m a l s t r e s s e s . Koss and Copley 3 have utilized this e x p e r i mental method with a C o - C r - C eutectic to d e t e r m i n e the " s t r e s s - r e l a x a t i o n t e m p e r a t u r e , " which c o r r e sponds to the point of initiation of p l a s t i c flow during heating in the p r e s e n t a n a l y s i s . T h e r m a l expansion m e a s u r e m e n t s a r e r e l a t i v e l y quick and s i m p l e to p e r f o r m . Moreover, the m e a s u r e m e n t a v e r a g e s over s m a l l inhomogeneities in m i c r o s t r u c t u r e which may influence t h e r m a l cycling deformation but a r e not as yet i n c o r p o r ated into the a n a l y s i s . It is the purpose of this paper to r e p o r t m e a s u r e m e n t s of the c o m p o s i t e coefficient of t h e r m a l expansion and to c o m p a r e the o b s e r v e d r e s u l t s to the a n a l y t i c a l p r e d i c t i o n s of the p r o p o s e d theory. 1 The coefficient of expansion of monolithic m a t e r i a l s is usually thought to be a s i m p l e function of t e m p e r a ture, 4 not r e l a t e d to any internal mechanical d e f o r m a tion or e x t e r n a l v a r i a b l e such a s heating or cooling r a t e (assuming uniform t e m p e r a t u r e is a p p r o x i m a t e l y maintained). As shown by the p r e s e n t m e a s u r e m e n t s , this is not the c a s e for c o m p o s i t e s . The n o r m a l i z e d G. GARMONGis Member of Technical Staff, ScienceCenter, Rockwell International, Thousand Oaks, Cafif. 91360. Manuscript submitted December 10, 1973. METALLURGICALTRANSACTIONS

elongation ( A l / l ) c of a composite c during a change in t e m p e r a t u r e in the a b s e n c e of e x t e r n a l loading is T2 c

T1

where a is the l i n e a r coefficient of t h e r m a l expansion, e is mechanical s t r a i n ,