*Result*: Mechanical response of composite structures under hydroelastic impact loading at constant velocities.

*Purpose: The flexibility of structure results in hydroelastic effect that significantly alters the hydrodynamic loads during slamming. These effects present challenges for the structural design of aircraft that need to account for water impact. The purpose of this paper is to solve the safety problem of aircraft landing on water. Design/methodology/approach: Based on the coupled Finite Element-Smooth Particle Hydrodynamics method, the hydroelastic effects of composite materials at high constant impact velocity are investigated. The influences of horizontal velocity, landing angle and pitch angle on hydrodynamic loads and deflections are quantified by comparing the structural response of flexible and semi-flexible plates. Findings: The hydrodynamic loads on the flexible plate increase rapidly, peaking as the plate approaches submersion and then sharply decrease once the plate is fully submerged. The descent angle significantly affects hydrodynamic loads, whereas pitch angle has minimal effect on constant speed slamming. In addition, maximum deformation occurs at the center of the plate, driven by local velocity and deadrise angle variations. The vehicle structure design should account for the appropriate thickness and landing attitude based on the specific usage scenario. Originality/value: The novel aspect of this work is the use of large-scale simulation models to achieve the water entry impacts of composite material with high horizontal velocities, providing guidance for the structural design of next-generation vehicles. [ABSTRACT FROM AUTHOR]*