Bending behavior of lightweight sandwich-walled shells with pyramidal truss cores

A study on the bending response of a composite curved panel with pyramidal metallic truss cores suitable for functional applications is presented using a combination of analytical modeling, three-point bending experiments and finite element (FE) based simulations. The aluminum pyramidal cores were constructed using an interlocking method before curing with composite face sheets to fabricate the final structure. A theoretical model was developed to analyze the experiments and develop failure criteria. Three failure modes: (i) face wrinkling, (ii) face crushing, and (iii) debonding between face sheet and truss cores, were considered and theoretical relationships for predicting the collapse load associated with each mode were developed. The experiments were carried out on two sets of specimens with differing face sheet thickness which clearly indicated the important role played by core debonding in determining the peak load of the structure. Localized buckling instabilities were also reported for samples with thinner face sheets. The role of debonding in determining strength was further highlighted by a comparison with FE simulations with suppressed debonding.