Theory of reinforcement damage in discontinuously reinforced composites and its application

In particle or short-fiber reinforced composites, cracking or debonding of the reinforcements is a significant damage mode because the damaged reinfor cements lose load carrying capacity. This paper deals with a theory of the reinforcement damage in discontinuously-reinforced composites and its appli cation. The composite with progressive cracking damage contains intact and cracked reiniorcements in a matrix. To describe the load carrying capacity of the cracked reinforcement, the average stress of a broken ellipsoidal in homogeneity in an infinite body which was proposed in the previous paper is introduced. An incremental constitutive relation of the composites with pr ogressive cracking damage of the reiniorcements has been developed based on Eshelby's equivalent inclusion method and Mori and Tanaka's mean field con cept. This damage theory can describe not only cracking damage but also deb onding damage of the reinforcements by modifying the load carrying capacity of damaged reinforcements. Influence of the reinforcement damage on the st ress-strain response and elastic stiffness of the composites is discussed. It is noted that the full-debonding damage gives the lower limit of the str ess-strain relation of the composite with progressive reinforcement damage.