the effect of interphase on residual thermal stresses. 2. unidirectional fiber composite materials文档.pdf

Mechanics ~[ Composite Materials, Vol. 33. No. 2. 1997 T H E E F F E C T O F I N T E R P H A S E ON RESIDUAL T H E R M A L STRESSES. 2. U N I D I R E C T I O N A L F I B E R C O M P O S I T E M A T E R I A L S 1 V. Kushnevsky* and A. K. Bledzki** In real composite materials an __additionalphase may exist between the fiber and the matrix. This phase, commonly known as the interphase, is a local region that resultsfrom the matrix bonds with thefiber surface or thefiber sizing. The differing thermal expansions or contractions of thefiber and matrix cause thermally induced stresses in composite materials. In the present study, a four-cylinder model is proposed for the determination of residual thermal stresses in unidirectional composite materials. The elastic modulus of the interphase is a function of the interphase radius and thickness. The governing equations in terms of displacements are solved in theform of expansion into a series [1]. The effective elastic characteristics are obtained using thefinite element approach. The effect of the interphase thickness and different distributions of the interphase Youngs modulus on the thermal residual stressfield in unidirectional composite materials is investigated. Introduction Composite materials have been extensively used in many applications, particularly, as structural components due to their high specific stiffness and strength. The residual stresses result from a difference between the moduli and thermal expansion coefficients of the fiber and the matrix. The differing thermal ex