Assurance of Iintegrity of Composite Pressure Vessels by AE Testing Using Remaining Life Indicator

Composite overpressure vessels (COPVs) are utilized in fuel cell vehicles (FCVs). The remaining life of COPVs decreases with repeated fillings. To indicate this decrease in remaining life, a remaining life indicator is embedded in the vessels. When the remaining life decreases, the indicator fractures before the structural components do. This allows for early detection, signalling the critical life of the vessel. Specifically, the indicator is designed to fracture before the carbon fiber, ensuring the vessel's strength. This fracture is then detected by AE (Acoustic Emission) testing, enabling us to determine the vessel's remaining life. In this study, we embedded the indicator in coupon specimens and conducted a preliminary study to assess the feasibility of our proposed method. As the indicator, we used a carbon fiber with a slightly smaller fracture stress compared to the carbon fiber comprising the vessels. Three types of coupon specimens with different amounts of indicator were prepared, and tensile tests were conducted. As a result, the fracture stress was not affected by the incorporation of the indicator, and the indicator's failure did not induce the fracture of the original CFRP (Carbon Fiber Reinforced Plastic). These results indicate that the integrity of COPVs can be ensured by incorporating the indicator and monitoring the fracture of these materials using AE testing.