A 3D Zig-Zag Sublaminate Model for Analysis of Thermal Stresses in Laminated Composite and Sandwich Plates

A laminated plate theory and 3D finite element model based on first-order zig-zag sublaminate approximations are presented for thermal stress analysis of composite laminates and sandwich plates. The finite element is developed with the topology of an eight-noded brick, allowing the thickness of the plate to be discretized into several elements, or sublaminates, where each sublaminate can contain more than one physical layer. The temperature field is first computed by a thermal model, where the through-thickness distribution of temperature is assumed to vary linearly within each ply, and continuity of transverse flux at ply interfaces is enforced analytically. Similarly, the in-plane displacement fields in each sublaminate are assumed to be piecewise linear functions and vary in a zig-zag fashion through the thickness of the sublaminate. The zig-zag functions are evaluated by enforcing the continuity of transverse shear stresses at layer interfaces. The formulation also enforces continuity of the transverse normal stresses, a key to accurate 3D predictions of the thermal stresses. The novel features of the formulation allow accurate and efficient prediction of the distribution of temperatures, displacements and stresses in laminated plates and sandwich plates wherein the plies have dissimilar thermal and/or structural properties.