Optimum Design of Carbon/Epoxy Composite Pressure Vessels Including Moisture Effects

The main target of the present study is to preserve the structural integrity of the composite pressure vessels (PVs) used in the seawater reverse osmosis (SWRO) desalination plants under internal pressure loading when moisture effects are taken into consideration. Different composite material lay-ups and fiber orientations are considered. In each case, the optimum safe thickness of the PV is found based on the appropriate failure criterion. The PVs are made of carbon/epoxy C/E IM7/977-3 with (±θ)ns lay-up. For verification purposes, PVs made from stainless steel SST 316L and carbon/epoxy C/E AS4/3501-6 are considered and their available results are compared with the predictions of the MATLAB code developed in this study. The study consists of three main cases. The first case considered the PVs materials SST 316L steel and C/E AS4/3501-6 carbon/epoxy composite, without moisturizing effect, with the purpose to verify the results of the developed MATLAB code by comparing with results from the available literature. The second case is concerned with the composite material C/E IM7/977-3, without moisture effects, while the third case included moisture effects on the same material (C/E IM7/977-3). The optimum angles found for C/E AS4/3501-6 is (±55.1)ns and for C/E IM7/977-3 with and without moisture are (±55.8)ns and (±54.0)ns, respectively. The best weight saving of the composite PV, when compared to the steel PV, reached 95.2%.