Impact of internal pressure regulation in filament winding on the quality of composite cylinders: a study with pulse-echo ultrasonic propagation imaging

To ensure the safety of composite pressure vessels considering the growing usage, this case study investigates how wet filament winding parameters affect quality of composite cylinders. Two 6.8-liter Type 4 cylinders with identical geometry and fiber stacking sequence were analyzed using pulse-echo ultrasonic propagation imaging. One cylinder was wound under constant internal pressure, while the other used increasing pressure to influence residual stress and influence imperfections. This difference led to distinct failure mechanisms in burst tests. The study focused on identifying porosity and resin-rich areas, visualized through ultrasonic wave propagation imaging and variable time-window amplitude mapping. Results revealed that the cylinder wound with increasing pressure had better composite consolidation but more resin-rich areas in the hoop windings. The findings demonstrate the effectiveness of pulse-echo ultrasonic imaging as a non-destructive method for detecting manufacturing-induced imperfections and highlight the importance of optimizing filament winding parameters to enhance composite quality.