The role of imperfect adhesion on thermal expansivities of transversely isotropic composites with an inhomogeneous interphase

The aim of this article is the prediction of the coefficients of thermal expansion of fiber-reinforced composites consisting of transversely isotropic fibers embedded into an isotropic matrix. The proposed model takes into account the existence of a non-homogeneous interphase lying in the area between the fiber and the matrix while the case of imperfect adhesions between the main constituents is considered and its effect on thermal expansivities is also examined. It was found that in the case of isotropic fibers there is no serious effect of the interphase existence on the overall thermal expansion behavior of the composites. On the contrary, in the case of transversely isotropic fibers, and especially for the transverse thermal expansion coefficient values, there exists a discrepancy between various theoretical predictions derived by other workers and from experimental results. In the latter case, the present model gives a better prediction showing that one of the reasons why different models fail to predict the thermal expansion behavior of fiber composites is ignorance concerning the existence of the interphase area. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.