Residual performance of composite pressure vessels submitted to mechanical impacts

Type IV pressure vessels are commonly used for hydrogen on-board, stationary or bulk storages. During their lifetime, they can be submitted to mechanical impacts, creating damage within the composite structure, not necessarily correlated to what is visible from the outside. When an impact is suspected, or when a cylinder is periodically inspected, it is necessary to determine whether it can safely stay in service or not. The FCH JU project Hypactor aims at creating a large database of impacts, characterized by various non destructive testing (NDT) methods, in order to provide reliable pass-fail criteria for damaged cylinders. This paper presents some of the tests results, investigating short term (burst) and long term (cycling) performance of impacted cylinders, and the recommendations that can be made for impact testing and NDT criteria calibration.