A higher-order sandwich plate theory accounting for 3-D stresses

In this paper we extend a layerwise higher-order shear-deformation theory to model the low-velocity impact of sandwich plates with an isotropic elastic foundation. A new concept of sublaminates is introduced, and the new sandwich plate theory satisfies the continuity conditions of interlaminar shear and normal stresses, accommodates the normal and shear stresses on the bonding surfaces, and accounts for non-uniform distributions of transverse shear stresses in each layer. A finite-element model based on this plate theory is derived for performing direct transient analysis in order to predict the initial failure mode, the initiation and location of critical matrix crack, and the threshold of impact damage. Moreover, shear warping functions, shear coupling functions, and thickness change due to in-plane stretching, bending, transverse shearing, and surface loadings are studied in detail.