Study on the low-velocity impact properties of GF/PP thermoplastic composite sandwich structure and the influence of impact damage on vibration characteristics

Thermoplastic composite sandwich structures are widely utilized in aerospace and other high-performance fields due to their advantages of lightweight construction, high strength, high flexural stiffness, excellent damage tolerance, and recyclability. The thermoplastic composite sandwich structure behaves ductilely under static load. However, under impact loading, it may exhibit brittleness or even lead to catastrophic failure. Therefore, in applications where impact considerations are paramount, the design of the sandwich structure must demonstrate good impact properties while also satisfying static and fatigue load requirements. Using a low-velocity drop-weight impact test, this paper investigates the impact response of sandwich structures with various panel configurations and different core thicknesses. Additionally, the influence of damage extent on the vibration characteristics of the sandwich structure under varying impact energies is examined with a vibrometer. The results indicate that the impact peak load of the sandwich structure increases with the panel thickness and core thickness, and the peak load for sandwiches with symmetrical configurations is greater than that for those with unidirectional configurations. The impact energy absorption capability of the sandwich structure is primarily influenced by its failure mode. When both the panel and core are damaged, the structure exhibits superior energy absorption properties. As impact energy increases, the vibration modal frequency of the sandwich structure decreases, while the damping ratio increases.