The relationship between the impact position interference and CAI strength of composite sandwich structures under double impacts

Sandwich structures are susceptible to multiple-impacts, and such multiple-impacts will typically occur at certain distances from each other. Therefore, the influence of five different distances between impact positions (DBIP) and three impact energies on compression after impact (CAI) strength are considered and discussed for honeycomb sandwich structure with composite face sheets in this paper. By comparing two typical impact characteristics, i.e., maximum impact force and displacement, the trend of CAI strength shows a turning-point, which is closely related to the size of the impactor. However, high impact energy (15 J) leads to damage in the bottom face sheet during the second impact, and the presence of damage in both top and bottom face sheet reduces CAI strength, resulting in the turning point of CAI strength not exist. It was observed that there is obvious buckling failure, and some cracks along the width direction from the impact point to the edge after CAI. To provide a more comprehensive understanding of double impacts and CAI behavior, a finite element (FE) model considering different DBIP is developed. In addition, the predicted fraction of energy absorbed by top face sheet, honeycomb core, and bottom face sheet is also obtained to reveal the relationship between the impact position interference and CAI strength.