Conventional and High-Frequency Eddy Current Testing of Composite Pressure Vessels

Speaker:
Pelkner, Matthias; BAM Bundesanstalt fur Materialforschung und -prufung; Germany

Authors:
Becker, B.; Federal Institute for Materials Research and Testing (BAM); Germany
Casperson, R.; Federal Institute for Materials Research and Testing (BAM); Germany
Pelkner, M.; Federal Institute for Materials Research and Testing (BAM); Germany
Pohl, R.; Federal Institute for Materials Research and Testing (BAM); Germany

ID: ECNDT-0317-2018
Session: Composite Material - EC
Room: G1
Date: 2018-06-14
Time: 09:20 - 09:40

Composite pressure vessels consist of an internal liner (Steel, aluminum, or plastic) which stores the liquid or gas and CFRP (carbon fiber reinforced plastics) which serves as pressure resistance. These vessels comprise some advantages compared with conventional vessels made of steel or aluminum and their application grew strongly over the last decade. The reason for this trend is the tremendous weight saving.
However, the long-time behavior for filling and discharging cycles and the creep strength of composite vessels is not fully understood [1]. Therefore, BAM started an internal project to investigate degradation of these material systems [2]. Normally, high-frequency eddy current testing (HF-ET, f > 10 MHz) is deployed for CFRP due to the low conductivity of the fibers, which is in the order of 0.01 MS/s, and the capacitive coupling between them. Nevertheless, in some cases conventional ET can be applied.
Some first results using conventional ET for detecting leakages in the internal liners are already presented [3, 4]. This contribution gives an update of our investigation using both conventional and high-frequency ET. Therefore, we developed an ET equipment based on a vector network analyzer using frequencies between 300 kHz and 2 GHz. The focus concerns the study of the aging effects.