On the role of long-term seawater exposure in the response of air-backed composites to hydrodynamic loading: An experimental study

Fiber-reinforced polymer composites are widely used in naval applications due to their high strength-to-weight ratio and resistance to corrosion. However, their long-term behavior under seawater exposure and dynamic loading remains elusive. Despite extensive research on pristine composites, few studies have examined the dynamic behavior of seawater-degraded fiber-reinforced polymer composites. Here, we investigate the influence of long-term seawater degradation on the dynamic response of fiberglass epoxy plates subjected to hydrodynamic loading in an air-backed configuration, mimicking the response to wave slamming or underwater explosions. The fiberglass epoxy plates were weathered in artificial seawater under accelerated conditions for up to eight weeks. Using three-dimensional digital image correlation and planar particle image velocimetry, we capture the coupled structural dynamics and flow physics of air-backed loading. Our results show that seawater degradation results in a significant reduction in stiffness, evidenced by larger displacements and a corresponding reduction in the hydrodynamic loading during the initial phase of the plate’s oscillation. These findings advance the understanding of fluid–structure interactions in seawater-weathered composites and underscore the importance of accounting for environmental degradation in the design of naval structures.