On Local Instability of the Deep-Profiled Facing of a Sandwich Panel

The paper deals with the problem of local instability of sandwich panels, which consist of two thin but relatively stiff facings and a thick but shear-deformable core. Such structures are commonly used in civil engineering, as well as in the aerospace, aviation, and automotive industries. A case is presented when one of the facings is deep-profiled. Due to typical mechanical or thermal interactions, this facing is subjected to compression. The thick core of the sandwich panel plays a stabilizing role; however, at a specific critical load, local stability is lost, which is a typical form of damage in sandwich panels. In the case of a deep-profiled facing, the geometry of the facing must also be taken into account, specifically the fact that the bends resulting from profiling constitute a significant limitation to its deformation. In the paper, expressions are derived that enable the determination of the critical (wrinkling) stress, taking into account the geometry of the compressed facing bands and various boundary conditions defined along their edges. The energy approach will be used to solve the problem. The presented solution to the problem will be illustrated with examples. The obtained results indicate that the use of narrow bands is particularly effective, but they also allow for determining the maximum benefits resulting from deep profiling of the facings. This information is essential when considering changes to the geometry of industrially produced sandwich panels or optimizing the load-bearing capacity of individual sandwich elements.