Bending characteristics of all-composite hexagon honeycomb sandwich beams: experimental tests and a three-dimensional failure mechanism map

The bending characteristics of all-composite honeycomb sandwich beams were investigated by a three-dimensional failure mechanism map and verified by three-point bending tests. In this paper, analytical models were used to predict the three-point bending stiffness, failure load and failure modes of all-composite hexagon honeycomb sandwich beams. A three-dimensional failure mechanism map was generated to characterize the dominant failure mechanism based upon failure load criteria for shear buckling, shear fracture, debonding, intracellular dimpling and face fracture. The tailor-folding method was used to fabricate the all-composite honeycomb sandwich beams. To verify the analytical models and three-dimensional failure mechanism map, three-point bending tests were carried out on the sandwich beams with different core relative densities, face thicknesses and loading spans. It was observed that the analytical predictions were in good agreement with the experimental results. A single case with the supreme load-weight ratio on the failure mechanism map has been identified and verified. Besides, the paths of maximum load design for a series of geometrical parameters were also traced. The study provides insights into the role of the physical dimension in tuning the flexural property of the sandwich structure and expands the application envelope of the failure mechanism map by effectively increasing the structural analytical dimensionality.