Abstract: Based on the concept of density gradient, three kinds of hybrid metal-fiber/polymer sandwich panel with arched and different density gradients of anti-tetrachiral honeycomb core layers were designed. The numerical model was established and the numerical simulation results were compared with the existing experimental results to verify the effectiveness of the model. On this basis, the effects of impact energies on the peak impact force, impact resistance, energy absorption and damage of different gradient arched sandwich panels were studied. At the same time, the dynamic response of the arched sandwich panel with the negative gradient under repeated impacts was further discussed. The results show that the gradient factor of the core layer has an important effect on the damage and failure modes of the sandwich panels due to the different core layer structures. Under low-energy impact loadings, the peak impact force increases with the increment of the gradient factor. Compared with uniform sandwich panels, gradient sandwich panels also have better energy absorption, and the energy absorbed can reach up to 32.8% than the uniform sandwich panels. At higher impact energies, the gradient factor has no significant effect on peak impact force and energy absorption. Under repeated impacts, the front facesheet and the core play a major role in the total energy absorption of the negative gradient sandwich panel, and the core layer accounts for 66% of the total energy absorption on average. As the number of impacts increases, the deformation and damage modes of the sandwich panel change from local deformation of the upper facesheet to failure,the deformation densification of the core layer to the overall collapse, and the overall lateral bending for the sandwich panel.

Key words: arched sandwich panel, gradient structure, energy absorption, repeated impact, numerical simulation, composites