To achieve CO2 emissions reductions, the automotive industries are moving towards more sustainable solutions. One of those are fuel cell electric vehicles (FCEVs) which rely on the chemical reaction of hydrogen to produce electricity. The hydrogen is stored in a gaseous and compressed form in composite pressure vessels (CPVs) which must be subjected to numerous tests for the certification. The end-of-line (EOL) test is a pressurization up to 105 MPa, compulsory for each tank before in-service life. This test could be used to quality assure the component and to verify the state of the CPV. Knowledge regarding damage formation and progression during a CPV pressurization must be obtained for the purpose. The goal of the research is to study which damage mechanisms take place and how their characteristics change when analyzing different layups. This is done pressurizing vessels with different stacking sequences in a specially designed testing chamber. During the test, optic and acoustic data are recorded. The acoustic emissions of the CPVs are detected using 120 sound pressure sensors and processed using a delay-and-sum beamforming algorithm. The optic data are analyzed with digital image correlation (DIC). The results show that only one damage mechanism takes place in the investigated pressure range (5-105 MPa). This has been identified as interfiber-fracture (IFF), happening both in the hoops and helical layers. Computer tomography scans have been used to validate the results. It is discovered that the grouping and the positioning of the hoop and helical layers has a significant influence on the acoustic behavior of the vessel. All the specimens of a layup follow a specific acoustic pattern: they have similar characteristics that can be used to associate a specimen to an analyzed stacking sequence. It has been shown that DIC has limited suitability regarding IFF detection in the hoop layers. It can identify IFF only if the hoops are the outermost plies of the laminate. However, it seems promising to predict the formation of other damage mechanisms such as IFF in the superficial helicals and delaminations. The findings contribute to a deeper understanding of the damage mechanisms taking place during an EOL pressurization. They also clarify the influence of the stacking sequence on the damage characteristics.

Fuel cell electric vehicles can provide the possibility to meet CO₂ emission reduction targets, but these vehicles require cost effective energy storage solutions. The current most mature technology uses compressed hydrogen, stored in composite pressure vessels (CPVs) manufactured by filament winding. Structural optimization of CPVs is important to meet both safety and cost requirements. This research aims to contribute to future CPV optimization strategies by investigating the effects of stacking sequence on the burst pressure and strain response. Two different winding angles were considered, related to a helical type winding and circumferential type winding, which were varied in sequence in terms of positioning and grouping. The manufacturing parameters were kept constant for all considered stacking sequences and were applied to a sub-scale pressure vessel geometry. Detailed experimental characterization revealed differences in burst pressure and strain measured with full-field digital image correlation with predefined deformation parameters. Analytical and finite element methods were used to capture related mechanical effects. The strain and burst pressure results from both approaches were correlated to conclude that the order of a sequence affects the structural performance, causing differences in CPV burst pressure of at most 49%. The results show that specific sequence choices can lead to higher burst pressures.