Residual burst pressure prediction of COPVs after long-term seawater immersion subjected to internal pressure

Composite overwrapped pressure vessels (COPVs) play a vital role in the development of lightweight energy equipment. Once deployed in seawater environments, their load-bearing performance inevitably deteriorates. Currently, most existing researches focus on the degradation of mechanical properties of composite laminates, while limited research has been conducted specifically on COPVs. In this paper, both experimental and numerical methods were conducted to evaluate the load-bearing performance and damage evolution process of COPVs after seawater immersion. Hydraulic burst test results indicated that the burst pressure of COPVs decreased by 10 % after immersion in artificial seawater at 60 °C for 200 days. As immersion time increased, the adhesion between fibers and matrix weakened, leading to fiber scattering. Additionally, the simulation results demonstrated high reliability in predicting the moisture absorption process and burst pressure. The residual burst pressure after long-term seawater immersion was predicted by the validated numerical method combined with the Arrhenius theory. The damage analysis results showed that moisture primarily reduced the burst pressure by exacerbating fiber tensile damage and reducing the initial internal pressure of matrix tensile damage. Due to the moisture gradient along the thickness of the winding layers during the moisture absorption process, the initial location of fiber and matrix damage shifted from the inner to the outer layers. Once this process reached saturation, the initial locations returned to the inner layer. This method provides a powerful tool for the design and burst pressure prediction of COPVs in marine environments.