THERMAL RESIDUAL STRESSES IN FILAMENT-WOUND CARBON-FIBER-REINFORCED COMPOSITES

Explicit algebraic expressions are first proposed to predict easily and precisely the thermal-expansion coefficients of unidirectional reinforced plastics. They are given as functions of the thermal and elastic properties of the constituent materials and of the fiber-volume fraction. They are derived by considering circular anisotropic fibers arranged in a hexagonal array in a matrix. Then, analytical expressions are derived for the thermal-expansion coefficients and curing stresses in filament-wound laminated composites under the assumption of elastic behavior and within the framework of laminated plate theory.

Experiments on carbon-fiber/epoxy composite cylinders reinforced by helical and circumferential windings show good agreement with the calculated values. The residual stresses induced by curing are found not to be negligible compared with the low tensile strength transverse to the fibers. Such algebraic expressions for thermal coefficients, together with those for elastic moduli and failure criterion proposed by one of the authors, seem to be of use in the tailored design of laminated composite structures in a closed form, which elucidate the effects of various sorts of constitutive parameters.