Rotational laser ultrasonic propagation imager in pulse-echo mode for defect evaluation of type-3 COPV

Type-3 composite overwrapped pressure vessels (COPVs) are increasingly being validated through research and practical applications because of their lightweight and high-strength properties. Based on these structural strengths, they are widely applied to the aerospace industry for the storage and transportation of fuel and high-pressure systems. Type-3 COPVs are manufactured by filament winding continuous carbon fiber layers onto the outer surface of a metal liner to withstand internal pressure and external structural loads. The composite manufacturing process makes these vessels prone to defects during winding. This emphasizes the need for precise non-destructive testing technologies to assess their structural integrity. This paper demonstrates the feasibility of using a pulse-echo (PE) mode inspection with a rotational scanning method based on laser ultrasonic testing. The depth-wise defect detection performance of PE mode with high-power laser integration was evaluated. Furthermore, PE mode was applied to inspect a type-3 COPV with artificial defects, and its applicability and practicality were validated through comparison with the through-transmission mode.