Experimental and numerical study on the constrained bending-induced collapse of hexagonal honeycomb

This study aims to analyze the deformation behavior of hexagonal honeycomb and classify the collapse modes during constrained bending for forming curved sandwich structures. To this end, the experiments with various bending radiuses and honeycomb thicknesses were carried out, and a finite element model (FEM) was developed to simulate the bending operation. To evaluate the honeycomb's buckling level, a novel quantitative approach was proposed based on the extracted deformed configuration of the honeycomb top surface. The FEM model was validated by comparing predicted deformation modes and quantities with experimental results and then used to analyze the honeycomb deformation. The buckling evolution, as well as its dependence on the honeycomb thickness and imperfection, has been extensively explored. It was found that the cell wall thickness variance has the most significant influence on the bending behavior. Furthermore, this study revealed two distinct honeycomb collapse patterns during the constrained bending process along the transverse direction (WD). The likelihood of each collapse pattern varies with bending radius and sample thickness. Besides, a snap-through buckling mechanism at the cell scale was proposed for the collapse onset and evolution. These achievements pave the way for the development of curved honeycomb sandwich structures.