Fibre anisotropic thermal expansion and residual thermal stress in a graphite/aluminium composite

Prediction of residual thermal stress in fibre-reinforced metal-matrix composites has previously assumed isotropy of the thermal expansion coefficients of both fibre and matrix. In the present study, the effect of anisotropy of the fibre thermal expansion on thermal stress is examined by extending a thick-walled cylinder model. For graphite/aluminium composites, the present model predicts transverse thermal stresses 75% lower for the anisotropic case than for the isotropic case. When these stresses are examined for incipient plasticity, it is found that anisotropy of the fibre thermal expansion results in a larger temperature range of elastic deformation during cooling from processing temperatures. With a consideration of viscoelastic effects, anisotropic fibre thermal expansion can result in the absence of plastic deformation after cooling from processing temperatures.