Experimental and Analytical Determination of Interfiber Fracture Mechanisms and Patterns in Type IV Composite Pressure Vessels

Abstract

The current needs of sustainable mobility lead to the electrification of transport industries, which require innovative products. The use of fuel cell electric vehicles (FCEVs) on a commercial basis depends on the development of hydrogen storage devices, which must be reliable and cost-effective. For the design of high safety composite pressure vessels (CPVs), it is necessary to have in-depth knowledge on the structural mechanics of these components. When internally pressurized for the first time, interfiber fracture (IFF) takes place within the structure of CPVs. The aim of the current investigation is to gain insights into the characteristic damage pattern and mechanisms that take place during CPV pressurization by analyzing the acoustic emissions and comparing the results to analytical and numerical solutions. Hence, a predefined number of vessels is manufactured and hydraulically pressurized in a specially designed test chamber up to burst. An array of 120 sound pressure sensors installed within the test chamber is responsible for recording the occurring acoustic events. By using a delay-and-sum beamforming algorithm, the events are localized. Their position and corresponding pressure level are analyzed and compared to analytical solutions calculated using classical lamination theory and 3D elasticity theory. Furthermore, a comparison to a finite element analysis is established. Therefore, insights are given into the application and correlation of these calculations to the experiments. Finally, the solutions are validated through damage observations using microsections and computer tomography. The findings contribute to a deeper understanding of the occurring damage mechanisms, the accuracy of the experimental method used and the damage progression due to different loading conditions of the CPVs under investigation.