Study on water-entry impact characteristics of composite sandwich nose fairing of cross-media vehicle via the ALE algorithm

This study uses a validated fluid-structure interaction algorithm to simulate the structural response of a sandwich composite nose fairing during water-entry impact. The analysis reveals that the top of the fairing and areas around the viewing window are primary load-bearing regions, with damage mainly as matrix cracking and delamination. Adding a PMI foam core reduces peak acceleration by 57.1% (from 58.62 m/s 2 to 25.15 m/s 2 ). Furthermore, the influence of entry velocity, entry angle, and sandwich material on the structural response to water-entry impact was systematically investigated. Impact acceleration shows a nonlinear positive correlation with entry velocity and decreases with increasing entry angle. Peak stress increases linearly with velocity and decreases with angle, being lowest under vertical entry. At entry velocities ≥12 m/s or angles ≤60°, the matrix is prone to severe damage or failure, and delamination is more likely. Among the materials tested, Agilus rubber offers the best load reduction, while 20R-PU (polyurethane with 20% rubber powder) composite best suppresses stress and damage propagation, yielding the best overall impact safety. These findings provide a reference for understanding impact load characteristics and damage distribution during low-speed water entry of cross-media vehicles, and support structural safety assessment, and engineering applications.