Design, Analysis, Manufacture, and Test of APC-2/AS4 Thermoplastic Composite Pressure Vessels for Deep Water Marine Applications

Abstract

A general design and analysis methodology is presented for the development of thick-wall thermoplastic composite pressure vessels for deep-water marine applications. A parametric study was performed to determine the optimum tapered radius, initial radial clearance, and plug length of the plug-supported end-caps employed here as end-closures since it was found that these optimum parameters could improve the performance of the composite pressure vessels by minimizing bending and shear stresses near the ends. Stress and buckling nonlinear finite element analyses (FEA) were performed taking hygrothermal effects into account. An equivalent coefficient of thermal expansion to model coefficient of moisture expansion for FEA software, where moisture absorption is not an input, is introduced to fully model hygrothermal effects. Based on the FEA results and taking the pressure vessel weight, ease of fabrication, mechanical and environmental performance, and cost into account APC-2/AS4 thermoplastic composite was found to be a suitable material system for the pressure vessel. An in situ thermoplastic composite filament winding/tape laying system employing infrared local and global heaters was developed in the Advanced Materials Manufacturing Laboratory of the University of Hawaii at Manoa, and was employed to manufacture the thick-wall composite pressure vessels. The manufactured pressure vessels had excellent quality, were instrumented by strain gages, and then successfully tested in the Hawaii Institute of Geophysics of the University of Hawaii at Manoa high-pressure water-filled pressure chamber. The strain gage results from the experiments were compared with those obtained from the FEA and excellent agreements were achieved.