Damage behavior of composite honeycomb sandwich structure subject to low-velocity impact and compression-after-impact using experimental and numerical methods

The paper studies the damage initiation and evolution of composite honeycomb sandwich structure subject to low-velocity impact and CAI (compression after impact) loadings by a combination of experimental and numerical methods. The impact responses including impact force and energy absorption were obtained through impact tests, and detailed damage analysis was conducted using various testing methods including ultrasonic C-scan, DIC (digital image correlation), infrared thermography and SEM (scanning electron microscope). A damage model based on MMF (micro-mechanics of failure) and cohesive behavior were used to predict the mechanical behavior of composite facesheets, and an elastoplastic constitutive model with ductile damage was used to model the honeycomb core. The experimental and numerical results show good agreements and reveal that the matrix damage, delamination, core crushing and fiber damage will be induced in the composite honeycomb sandwich structure depending on the impact energy levels. During the CAI process, the strain concentration in the impact region will lead to local buckling of the sandwich structure, and the damage expands from the impact region to the free edges along the transverse direction until the final collapse, which will cause an obvious temperature increase in the damage area.