Thermal Expansion Coefficients and Residual Stresses in Filament-Wound CFRP Materials

Abstract

The thermal expansion coefficients (α) of unidirectional reinforced plastics are obtained easily and precisely by the use of explicit algebraic formulae which are functions of thermal and elastic properties of the two constituent materials and of their volume fractions. They are derived by considering uniformly spaced circular anisotropic fibers arranged in a hexagonal array in an elastic matrix. Then the analytical formulae for the thermal expansion coefficients and the residual stresses in filament-wound and laminated composites are given under the assumption of elastic behavior and within the framework of the laminated plate theory.
The experiments on carbon fiber/epoxy laminated composite cylinders which are reinforced by helical and circumferential windings show a good agreement with the calculated values. The residual stresses induced during the curing process are found not to be negligible compared with the weak tensile strength normal to fibers. The algebraic formulations for α together with those for elastic moduli and failure criterion proposed by one of the authors seem to be useful for the optimal design of laminated composite structures in a closed form which elucidate the effects of various sorts of constitutive parameters.