On the Response of a Sandwich Panel With a Bilinear Core

Sandwich panels can fail in a variety of ways. In the present paper one type of failure is investigated and modeled which has a number of important applications, e.g., marine hulls. Here core yielding is assumed to initiate and grow in the sandwich panel while the face sheets remain bonded, unbuckled and in the elastic range. For elastic face sheets, the core shear stresses can be determined from equilibrium of the face sheets independent of core yield. Core shear strains can then be found from the stress-strain curve and an algorithm is constructed for determining shear deflection. Bending deflection is found from the elastic solution. This approach works well except when the bilinear stress strain behavior approaches the perfectly plastic core. With the aid of a detailed finite element solution it is shown that the classical sandwich theory assumptions begin to break down and that the face sheets now carry an appreciable part of the shear load. This effect is shown in detail for four point beam bending where the classical sandwich solution is 20∼30% below the ABAQUS results and the experimental data. For the bilinear case, not close to perfectly plastic, however, the extension of the classical theory to the core yielding problem provides excellent results.