Water‐Borne Erosion of Reinforced Polymer Composites: Application to Shallow Offshore Marine Environment

ABSTRACT Polymer composites remain promising materials for numerous mechanical and structural applications, and significant research efforts have been directed toward investigating the resistance of these materials to air‐borne solid‐particle erosion. However, the literature lacks detailed information on the behavior of fiber‐reinforced polymer composites when subjected to water‐borne sand erosion (e.g., in marine environments), including the effects of shallow impact angles and zero‐to‐low sand concentrations. Therefore, this paper presents the erosion performance of epoxy‐carbon (and ‐glass fiber) composites under controlled marine‐like conditions, focusing on the effects of impact velocity (i.e., 2 and 6 m/s), sand concentration (i.e., 0, 0.05, and 0.4 g/L), and impact angle (i.e., 5°, 30°, 60°, and 90°). Experimental results demonstrated that erosion rates were strongly influenced by test conditions, with carbon fiber‐reinforced polymer (CFRP) exhibiting superior resistance compared to glass fiber‐reinforced polymer (GFRP), particularly at higher velocities, oblique angles, and increased sand concentrations (0.4 g/L). The clean water erosion peak occurred at 90° due to maximum normal impact forces. In contrast, the water–sand erosion in both composites showed semi‐ductile erosion behavior as the 60° angle produced the highest erosion rates. High‐resolution surface profilometry and scanning electron microscopy (SEM) revealed distinct erosion mechanisms, indicating that tangential microplowing dominated shallow angles (5°) erosion. In comparison, oblique angles exhibited mixed ductile and brittle failures, including matrix cracking, fiber delamination, and crater formation. Additionally, an improved empirical erosion model effectively predicted clean water and water‐borne particle erosion scenarios with good agreement with experimental data.