Energy absorption and collapse behavior of PP-based pin-reinforced composite sandwich panels under quasi-static flatwise compression loading

This article investigates the energy absorption and failure behavior of thermoplastic composite sandwich panels made entirely of polypropylene (PP) and pin-reinforced core under quasi-static compressive loading. The pins are manufactured by thermoforming and assembled with face sheets. The specimens were subjected to flatwise compressive loading to examine energy absorption capabilities. Moreover, the finite element method (FEM) is used to analyze core sandwich panels reinforced with cubic, cylindrical, beam, and cross-beam pins. Furthermore, a closed-form analytical model is adopted and developed to predict the critical load of these structures. The performed experiments were utilized to validate the damage mechanisms and critical displacements of the simulations and the analytically calculated maximum collapse loads. The results demonstrate that the predictions accurately capture both the critical failure load and failure mechanisms. Since the numerical results have a reasonable correlation with the experimental results and their output difference is < 15%, FEM is used to investigate the collapse behavior of the pin-reinforced foam-filled panels. A comparison of the load-displacement, specific energy absorption (SEA), and maximum collapse loads of the samples shows that the cubic reinforced foam-core sandwich panel has the maximum peak load and SEA. The FE model of pin-reinforced foam-filled panels reveals that the buckling of the reinforcements is postponed to a point beyond the critical one. Hence, PP foam can act as lateral support and delay the ultimate failure in panels, especially pin-reinforced cylindrical sandwich panels, up to 40%.