In order to solve the problem of the face/core bonding performance of the sandwich structure, this paper proposed a M - pattern folded sandwich structure. Structural performance in direct (pure) shear was investigated for sandwich structure. FE-Analytical of sandwich structure strength under shear loading condition was presented for possible failure modes. Panels with core of different thickness were tested for different failure modes and the mechanical properties. In general, the measured failure loads showed good agreement with the FE-analytical predictions.The results shown that failure modes of the sandwich structure with low relative density were shear buckling and fracture of thin-walled of cores, respectively. For the sandwich structure with high relative density, the dominant failure mode was interfacial debonding of face/cores, and the initiating failure along the ends of the specimens.

In order to solve the problem of the face/core bonding performance of the sandwich structure with chevron folded core, this paper proposed a M-pattern folded sandwich structure. Compression responses of fabricated folded cores were measured, and FE-analytical models were presented to predict the stiffness, strength and dominant failure modes under flatwise loading. The results show that the M-pattern folded sandwich structure has a high anti-buckling performance, and the dominant failure mode of the structure is crushing of the cell walls. The sandwich-panel cores investigated appear to be promising candidates for lightweight systems and multifunctional applications.

Bending properties and failure modes of sandwich structure with carbon fiber composite M-type folded cores were investigated and presented in this paper. Three point bending responses of both sandwich beams were measured. The finite element method was utilized to determine deformation mode of sandwich beam with M-type folded cores. Cores buckling and debonding have been studied under three point bending and the maximum displacement was also studied using FE-analytical and experimental methods.