Thermally induced changes in the focal distance of composite mirrors: composites with a zero coefficient of thermal expansion of the radius of curvature

摘要

The article calculates the Coefficient of Thermal Expansion (CTE) of a radius of curvature of a quasi-isotropic composite. CTE $APEQ $alpha$-1$/ $PLU ($alpha$-1$/ $MIN $alpha$-3$/)/2 $DOT E$-3$//E$-1$/ $DOT (1 $MIN $nu$-12$/)/(1 $PLU $nu$-31$/), where indexes 1 and 2 refer to the in-plane properties, index 3 refers to the out-of-plane properties, $alpha@, E, and $nu are correspondingly the CTE, the stiffness, and the Poisson ratio. The differences between the zero in-plane CTE and zero radius of curvature CTE composites are described. Under some conditions, the CTE of the focal distance of a sandwich mirror made from this composite is identical to that of the composite itself. This article gives the approximations as well as the conditions when the CTE of the focal distance and the composite are identical.