Development of a Computationally Efficient Modelling Framework for Type IV Pressure Vessels

Abstract

The combination of a relatively recent emissions scandal and the ever growing incentive to provide sustainable transportation solutions, led to the fact that the transition to electrically propelled land-based vehicles is more prominent than ever. All prominent European car-makers announced diverse fully and partially electric product portfolios for 2021 and beyond with strong indication that the era of the Internal Combustion Engine (ICE) is slowly fading into history. While Battery Electric Vehicles (BEVs) are already well on their way in establishing a strong market share in the personal vehicle domain, the field of long haul transport is left to search for solutions elsewhere as battery technology does not present an efficient solution at this time. Fuel-Cell Electric Vehicles (FCEVs) pose a solid performance base to close the gap that batteries cannot
and provide sustainable, zero emissions solutions, for all heavy transport sectors - automotive, aviation and maritime. Within fuel cell systems, a component whose criticality is often overlooked or even understated is the hydrogen storage tank. Current state of the art uses type IV composite pressure vessels (CPVs) with a plastic liner and Carbon Fiber Reinforced Plastics (CFRP) composite overwrap to ensure structural integrity. Recognizing the complexity of a CPV is crucial in order to allow for the development of robust and worthwhile
design processes that could yield a significant decrease in material use, making FCEVs more cost effective and an attractive long-term solution. This thesis aims to provide some detail on the behavior of CPVs and their depth through the development of an automated numerical analysis framework and the execution of a focused experimental study that examines the impact of laminate stacking sequence as well as manufacturability factors on overall CPV behavior and, in particular the cylinder-dome transition of the vessels. The details and experimental correlation of the developed numerical analysis framework are shown and discussed. The framework heavily utilizes the outputs of an industry standard filament winding software, Composicad, which is used as a basis that is then further refined in order to generate a satisfactory geometric description of the vessel and its laminate composition. Major emphasis is placed on the discussion of processes made for the geometry correction and attention is placed on particular factors that were also tested in the experimental study - hoop ply drop-off and stacking sequence. The framework is correlated to experimental results and laminate configurations from previous and current experimental results to showcase its versatility and potential for future optimization studies given the high level of automation involved. Two Finite Element (FE) models are investigated within the scope of the developed framework - a solid and shell element model. The performance and predictive ability for each are presented and discussed. The experimental study presents data on the impact of stacking sequence effects and hoop ply drop-off
on CPV behavior - in particular, the cylinder-dome transition. The influence of both parameters are discussed and contextualized with previous studies in order to identify relevant trends. Novel results were obtained for the relationship between hoop layer placement and burst performance. The results further indicate a delicate interaction between vessel stacking sequence, burst strength and manufacturing robustness. The results of this study highlight important factors for future numerical studies of CPVs and showcase the development of an analysis approach with low computational cost while retaining acceptable accuracy. Furthermore, the experimental study helps put focus on future areas in need for further investigations in order to identify design-critical performance trends.