Analysis of Thermal Expansion Coefficients of Short-Fiber Composites Using Micromechanics

Abstract

A Material, which has zero or very small thermal expansion coefficient, is expected in parts for precision machines and optical instruments. An analytical model for a short fiber composite is developed to evaluate thermal expansion coefficients by applying the Eshelby's equivalent inclusion method to two kinds of inhomogeneities, i.e. fiber and filler. It is assumed that the inhomogeneities distribute uniformly within the limits of an arbitrary orientation angle in the 2-D plane. Good agreement between the theoretical results based on the present model and experimental ones is obtained. The effects of distributions of fiber-orientation, fiber-aspect ratios, volume fractions and Young's moduli on thermal expansion coefficients are investigated for a carbon fiber/epoxy resin composite. The possibility of realizing zero and very small thermal expansion coefficients in the short-fiber composite is shown in case that fiber-aspect ratios are relatively large and fibers are almost aligned.