The catastrophic failure of thick composite cylindrical pressure hulls: Analytical, numerical and experimental investigations

The catastrophic failure of thick composite cylindrical pressure hulls under high external hydrostatic pressure was investigated by analytical, numerical and experimental methods. Buckling failure and material failure were both considered to identify which failure mode of such thick hulls initiates first. An elastic buckling analytical model for thick composite cylinders based on Sander theory principles was applied to derive the critical buckling load. Meanwhile, a progressive damage model (PDM) was developed to simulate the material behavior in the region between the first-ply failure and ultimate failure, and the effects of failure criteria and geometrical defects on the implosion load of the test model were investigated. Then ultimate strength were obtained by comprehensive analysis of buckling failure and material failure via analytical and numerical methods. A group of two thick T700 carbon fiber/epoxy composite cylindrical pressure hulls were designed and manufactured, hydrostatic pressure tests were conducted to derive the catastrophic failure characteristics of thick composite pressure hulls and to validate the analytical and numerical results and methodology for the failure analysis of thick composite cylindrical pressure hulls.