Mechanical Performance of Bio-inspired Bidirectional Corrugated Sandwich Pressure Shell Under External Hydrostatic Pressure

This paper aims to enhance the compression capacity of underwater cylindrical shells by adopting the corrugated sandwich structure of cuttlebone. The cuttlebone suffers uniaxial external compression, while underwater cylindrical shells are in a biaxial compressive stress state. To suit the biaxial compressive stress state, a novel bidirectional corrugated sandwich structure is proposed to improve the bearing capacity of cylindrical shells. The static and buckling analysis for the sandwich shell and the unstiffened cylindrical shell with the same volume-weight ratio are studied by numerical simulation. It is indicated that the proposed sandwich shell can effectively reduce the ratio between circumferential and axial stress from 2 to 1.25 and improve the critical buckling load by about 1.63 times. Numerical simulation shows that optimizing and adjusting the structural parameters could significantly improve the advantage of the sandwich shell. Then, the hydrostatic pressure tests for shell models fabricated by 3D printing are carried out. According to the experimental results, the overall failure position of the sandwich shell is at the center part of the sandwich shell. It has been found the average critical load of the proposed sandwich shell models exceeds two times that of the unstiffened shell models. Hence, the proposed bio-inspired bidirectional corrugated sandwich structure can significantly enhance the pressure resistance capability of cylindrical shells.