Voids in type-IV composite pressure vessels manufactured by a dry filament-winding process

Type-IV high-pressure hydrogen-gas tanks for fuel-cell electric vehicles are made from carbon fiber-reinforced plastic. Their production involves wrapping a carbon-fiber-reinforced thermoset resin towpreg around a plastic liner to form a tank shape, followed by heating in an oven to cure the thermoset resin. The filament-winding process produces many voids in the tank that cause variations in quality and the product lifetime. In this study, the voids in the tank were classified according to their origin. A type-IV high-pressure hydrogen-gas tank with a burst pressure of 70 MPa was fabricated, and the voids produced in the tank were observed. The same filament-winding process was used to fabricate a plate and tank with a simple winding trajectory to identify the voids. The voids produced in the tank by the filament winding were categorized into six groups based on their location, cross-sectional shape, and size, showing the origin of the voids.