Folded Core Sandwich Panels
Foldcore sandwich panels consist of a partially folded core, most commonly based on the Miura pattern, sandwiched between two stiff facings. They have been investigated in the aerospace and composite engineering industries as a potential substitute to honeycomb panels, as they possess a number of favourable properties that are not possible with other types of high-performance sandwich panels.
An indented foldcore is a modified Miura-type foldcore geometry in which sub-folds into along core ridges. This geometric modification triggers a high-order travelling hinge line failure mode which has a much higher and more uniform energy absorption than the plate buckling failure mode seen in a standard foldcore structure. Further information: DOI:10.1016/j.ijimpeng.2014.06.001.
An experimental and numerical study of foldcore performance under quasi-static crush loads showed that all foldcore types were highly sensitive to geometric imperfections, and that curved-crease foldcores had significantly higher energy-absorption capability than straight-crease foldcores. An optimum configuration of the curved-crease foldcore was found which offers comparable out-of-plane strength, energy-absorption under quasi-static compressive loads, and stiffness to a honeycomb core. Further information: DOI:10.1016/j.ijsolstr.2014.10.019.
A range of kirigami-inspired folded core structures was explored use in sandwich panels as alternatives to the widely studied Miura-ori folded core. Two cores were direclty based on cube and eggbox kirigami patterns and two cores were based on geometric modifications of the cube pattern. A non-optimised diamond strip cube strip core offered a 41% increase in average force compared to the best-performing curved-crease Miura-type foldcore previously reported and a 92% improvement over the standard Miura-type foldcore. Futher information: DOI:10.1016/j.ijmecsci.2015.08.013.