On the influence of flow-front orientation on stringer stiffened composite panels in water impacts

Water impacts form the critical load case for high-performance carbon fibre reinforced polymer (CFRP) racing craft. Such events produce a peaked, non-uniform pressure distribution that travels along a hull panel as it is immersed. Current design standards are based on static, uniform pressure loads that do not account for the directional nature of water impacts. With recent trends towards the use of directionally stiffened hull structures in the form of stringer stiffened composite panels (SSCPs), such simplifications of the load case may no longer be valid. In this study, a marine-based SSCP was tested experimentally and numerically to investigate the effects of flow-front orientation on high-performance hull panels. Parallel and perpendicular impacts at constant velocity were carried out using the novel Servo-hydraulic Slam Testing System (SSTS) and the results were used to validate a one-way coupled computational fluid dynamics — finite element analysis (CFD-FEA) Fluent/Abaqus solution. The highest strains in the monolithic skin and stringer were observed for perpendicular impacts. A parameter sweep across a range of impact orientations between parallel and perpendicular impacts was carried out. An approximately linear relationship between flow orientation angle and key structural strains was observed, with the highest strains reported at 70–90°. Results indicate that the critical load case for SSCPs occurs at 75°orientation angles, where strains in the stringer capping are maximum.