High-strength and high-toughness spray-type polyurea coating for impact protection of aluminum sheet

This study aims to synthesize polyurea coating material with superior impact resistance for protecting aluminum sheets. Polyurea was synthesized with various ratios of amino-terminated polyether and amine chain extender using the semi-prepolymer method. The optimal composition ratio of polyurea with excellent impact resistance was determined by comparing the basic properties and the quasi-static and dynamic tensile mechanical properties of polyurea. A high-strength and high-toughness polyurea was applied to the aluminum sheet's surface using a high-temperature and high-pressure spraying machine, resulting in a polyurea-coated aluminum sheet. Its protective performance was tested under impact load using split Hopkinson pressure bar method. The effects of different polyurea coating methods on the failure morphology, velocity effect, and energy dissipation law of aluminum sheets were analyzed to guide the engineering application. The research findings demonstrate that coating polyurea on aluminum sheets' front face (load-receiving face) can alleviate stress concentration during the impact process of flat warheads on aluminum sheets and improve the punching shear resistance of aluminum structures. The critical velocity of aluminum sheets can be improved by coating polyurea on the front face and both faces. Moreover, polyurea coating on the load-receiving face of aluminum sheets can improve energy consumption efficiency. The impact resistance of aluminum sheets with different hardness polyurea coatings was further analyzed through finite element simulation. In engineering design, we recommend using harder polyurea on the front face and softer polyurea on the opposite side of the aluminum sheet based on our simulations.