Low-velocity impact behavior of X-Frame core sandwich structures - Experimental and numerical investigation

X-Frame core sandwich structures are fabricated with carbon fiber reinforced polymer (CFRP) face sheets and aluminum alloy cores. The hybrid combination enables composite face sheets to maximize specific flexural stiffness and X-Frame metal core to improve the impact resistance. The effects of impact energy, impact site and face sheet material type on the impact response and resulting damage state have are investigated experimentally and numerically. The low-velocity impact tests are carried out to study the impact response in terms of the impact load, absorbed energy and failure modes. Meanwhile, finite element analysis is implemented to simulate the impact behaviors and failure mechanisms by the VUMAT subroutine in ABAQUS/Explicit, using a progressive damage model based on the Hashin and Yeh delamination failure criteria. For comparison, all-metallic sandwich structures are also studied to better understand the influence of face sheet materials. These studies reveal that impact response and resulting damage state are strongly dependent on the impact energy and impact site. Composite sandwich structure absorbs more impact energy than aluminum sandwich structure for the perforation case, indicating that the former has better impact resistance. The predicted results of the low-velocity impact response are fairly consistent with the experimental measurements, which suggests that the numerical procedure could be a helpful tool in developing novel lightweight multifunctional structures.