BEHAVIOR OF DELAMINATED SANDWICH BEAM WITH TRANSVERSELY FLEXIBLE CORE - HIGH-ORDER THEORY

The bending behavior of a general sandwich beam, delaminated (debonded) at one of the skin-core interfaces, with transversely flexible core, based on variational principles is analytically investigated. The beam construction consists of upper and lower, metallic or composite laminated symmetric skins, and a soft core of a foam or low-strength honeycomb type. The delamination considered is a crack (debond) in which the crack faces may be in contact vertically, but can slip horizontally with respect to one another. The elastic analysis consists of a two-dimensional formulation for the core, in longitudinal and transverse directions, combined with a beam theory formulation for the skins. The effects of the vertical flexibility of the core, in the undelaminated and the delaminated regions, with and without contact, on the behavior are considered. The use of a high-order theory yields a non-linear displacement field in the core, in the undelaminated region, and determines the shear and the peeling (normal) stresses at the skin-core interfaces in the delaminated and the fully bonded regions, as well as at the crack tips. Any type of loading, distributed, localized or concentrated, located either at the upper or the lower skin, or at both, as well as any type of boundary and continuity conditions differing from one skin to the other and to the core at the same section, are allowed. The effect of the delamination length and location on the overall behavior and on the peeling stresses at the skin-core interfaces, are studied.