Thermal Expansion Coefficients of Unidirectional Composites

Abstract

An analytical and experimental investigation on thermal expansion coef ficients of unidirectional composites (UD) is carried out. The fiber aniso tropy and temperature dependency of the constituent material properties are considered in the formulation of the problem. The solving technique used here is constructed by a slight modification of the one which was once developed and employed by the authors for calculating elastic moduli of UD. It is shown that α _z of UD is approximately given by the modulus modified law of mixture, and that α _x's based on the hexagonal and square array models are almost identical. Some relationships between α's of UD and the constituent material properties are graphically indicated. The first point of the main purpose of the experiments is to reveal certain tempera ture dependent behavior of α's of the constituents of the Carbon-Epoxy. The second is a comparison between the experimental and theoretical re sults of an influence of α_m on α _x and α _z. The third is to estimate unknown α_fr and α_fz of the carbon fibers. A testing apparatus used here is an interferometric dilatometer using gas Laser which is sensitive enough to measure temperature dependent α's.