Description
The present work deals with the high-velocity impact (HVI) behaviour of composite sandwich structures based on experimental and numerical method. The composite sandwich structure consists of two ultra-high molecular weight polyethylene (UHWMPE) laminates and a PET (polyethylene terephthalate) foam core. A series of HVI tests were conducted on the UHWMPE/PET foam sandwich structures to investigate the HVI performance and damage mechanisms. Micro-computerized tomography (μCT) characterization method was used to detect the internal damage patterns in the sandwich structures. A finite element model (FEM) was developed which Puck’s failure criteria simulates intra-layer failure, cohesive law simulates inter-layer failure and the crushable foam plasticity model combined with ductile damage criterion simulates the foam failure. After validation of the proposed model by experimental results, the damage mechanism of the sandwich structures under HVI loading was examined, and the effects of impact velocity on the failure patterns and residual velocity were discussed. Several key conclusions from this study are summarised as follows: 1. Circular hole-type damages were only observed on the upper panel, even though the impactor penetrated the composite sandwich structure. On the lower panel, only linear crack-type damage along the fibre direction were generated due to the rebound of the stretched fibres after the impactor penetrated. 2. Generally, the peak impact force and energy absorption values increase with higher impact velocity. However, when the impact velocity is less than the critical value (Critical velocity =200 m/s for the composite sandwich structure in the study), both the impact force load and energy absorption values remain relatively stable and are not significantly influenced by variations in impact velocity. 3.Foam cores in composite sandwich structures generate an upward rebound force during HVI when they are compressed to a certain extent, resulting in the appearance of a third peak in the impact load curve and absorbing more energy. 4.The presence of UHMWPE fibre interspersed in the panel tended to inhibit the spread of damage in the impacted region. Only matrix tension damage showed noticeable propagation during HVI, and matrix tension damage increased with the impact velocity, reaching a plateau when the velocity exceeded 250 m/s.
