On the Apparent Bending Isotropy in Clamped Elliptic Composite Laminates

Abstract

The flexural behavior of clamped elliptic composite laminates is studied. Both symmetric and asymmetric laminates are investigated. Closed form solutions are discussed for laminates subjected to uniform transverse loading. The appparent bending isotropy is identified for clamped elliptic laminates for which the deflection can be represented by an equivalent isotropic plate. An invariant characteristic bending stiffness is found for circular symmetric laminates. It is shown that the characteristic bending stiffness of quasi-isotropic laminates can be obtained directly from the in-plane effective moduli of the laminate. For laminates under nonuniform loading, the apparent bending isotropy may not exist. However, a numerical study shows that, for clamped circular π/4 quasi-isotropic laminates subjected to axisymmetric loading, the solution of isotropic plates can be adopted as a good approximation.