One-dimensional response of single/double-layer cellular cladding to water blast

Abstract

One-dimensional (1D) response of single/double-layer cellular claddings to water blast, including the core crushing, fluid-structure interaction (FSI) and cavitation phenomenon, is investigated by analytical approaches and finite element (FE) simulations. Analyses are focused on the shock mitigation mechanism of cellular cladding and optimization design of double-layer cladding (DLC) with particular interests in shortening cladding thickness without increasing the transmitted stress to the main structure.It is demonstrated that the actual incident wave impinged on the cladding and interface pressure at the wet face are highly dependent on the core crushing, FSI effects and cavitation phenomenon under identical incident wave. The actual incident wave will be enhanced due to the collapse of cavitation bubbles, especially for soft core. The total pressure at the wet face typically exhibits a rapid decline followed by a long pressure plateau whose value approximately equals to the quasi-static stress of the core being compressed. The high pressure loading incident on the cladding is converted into a lower magnitude load with much longer duration, which is beneficial for shock mitigation.Parametric analyses of the single-layer cladding (SLC) indicate that strong core cladding can largely shorten the total foam thickness needed to dissipate the shock energy. However, the transmitted stress to the main structure increases correspondingly. Therefore, a DLC with strong core being placed at the impinged end is proposed to shorten the foam thickness without increasing the transmitted stress. Comparisons of shock mitigation ability between the DLC and its single counterpart are conducted in terms of the total foam thickness, partial impulse imparted to the cladding and absorbed energy. The results reveal that the DLC can absorb more energy and reduce the total foam thickness when the face sheet of the soft core is properly designed. Finally, design guides for the DLC against water blast are presented.