Study on Water Hammer Effect of an Aircraft Composite Fuel Tank under High-Speed Impact of Multiple Fragments

The investigation examines the damage mechanisms of composite fuel tanks under high-speed impact by multiple fragments utilizing a fluid-solid coupling finite element approach. The Arbitrary Lagrangian Eulerian (ALE) algorithm is used to simulate the single-box composite fuel tank under the impact of different distribution distances of fragments by using the software LS-DYNA. The cavity evolution and the panel deformation of the composite fuel tank are analyzed in detail. The findings indicate that the water hammer effect amplifies the extent of damage to the composite fuel tank structure. During the initial phase following fragment impact, a cavity forms within the tank. The resulting rise in the pressure difference between the interior and exterior of the tank causes the liquid to impinge on the impacted panel, leading to its deformation. In the later stage, due to the large degree of damage to the incident panel, there is a certain degree of pressure relief inside the fuel tank, the degree of water hammer effect is obviously reduced, and the cavity in the fuel tank gradually disappears. The distribution distance of the fragments has a great influence on the damage effect of the fuel tank. As the spacing between fragments diminishes, their effects become more concentrated. This results in increased force from the liquid on the fuel tank panel, leading to greater deformation and more severe damage to the panel.