The effect of impactor shape on the low-velocity impact behavior of hybrid corrugated core sandwich structures

Corrugated core sandwich structures are fabricated with carbon fiber reinforced polymer (CFRP) face sheets and aluminum alloy cores. This lightweight design concept enables sandwich structures to maximize their specific bending stiffness/strength and improve their energy absorption capability. A combined experimental and numerical study is performed to investigate the effect of impactor shape on low-velocity impact behavior. Low-velocity impact tests are conducted to study the impact resistance when impacted by conical, hemispherical and flat impactors. A user subroutine VUMAT is developed to model the CFRP face sheet behavior, in which a progressive damage model based on the Hashin failure criteria and Yeh delamination failure criteria is implemented in ABAQUS/Explicit. Reasonably good agreement is achieved when comparing impact force, absorbed energy, and failure modes between experimental measurements and numerical predictions. These studies reveal that damage, consisting of fiber damage, matrix damage and delamination of the face sheets as well as buckling of core members, depends on the impactor shape, impact energy and impact location. The investigations provide some insight into the failure mechanisms in this hybrid sandwich structure under low-velocity impact loading, which could be used in the development of novel lightweight multifunctional structures.