Formation and relaxation of residual facesheet dent on foam-core sandwich structures by localized transverse loading

Abstract

A residual facesheet dent on an indented or impacted foam-core sandwich structure significantly affects the residual mechanical properties and the detectability of the damage. However, previous studies have not sufficiently addressed residual dent formation during unloading and the subsequent relaxation. This study quantitatively clarifies the mechanism underlying the formation and the relaxation of a facesheet dent using a segment-wise modeling approach that was formulated for honeycomb sandwich structures in our previous study. We utilize fully backed foam-core sandwich beams under static indentation loading, focusing on the interaction between local deformation of the facesheet and crushing/stretching of the core. This study begins by evaluating the indentation response using quasi-static tests. The indentation behavior is then predicted by extending our previous model. The underlying mechanism of facesheet dent formation and relaxation is quantitatively discussed from the viewpoint of a reaction force from the core to the facesheet.