MOBILITY AND TRANSPORT: The importance of composites for fuel cell electrical vehicles (FCEV’s)
Themes: Mobility & Transport
In the context of clean and sustainable mobility, the automotive industry is looking at alternatives fueling solutions. Technologies involving compressed gasses (e.g. methane or hydrogen) are currently pursued which require high-pressure storage tanks for 200-700 bar. For mass reduction reasons, mainly CPV’s with carbon fiber reinforced plastics (CFRP) structure are being considered, offering potential weight savings of up to 80% compared to steel tanks. The back draw of CPV’s is the high cost of carbon fiber. The present paper discusses the possibilities to use different aspects of numerical modelling to optimize performance and cost of CPV’s without compromising any safety features.
The architecture of a CPV comprises 4 different components:
- Liner (thermoplastic or metallic) as permeation barrier
- Boss parts (aluminum or steel) to connect the valves
- CFRP structure to resist the pressure
- Protection caps (low density plastic) for impact resistance
Since these elements have specific functionalities, different materials are used depending on the required properties. Only an in depth Finite Element Analysis (FEA) based on detailed numerical modelling is able predict if the CPV will comply with safety requirements of strength (burst pressure) and durability. As carbon fiber is the main cost driver of a CPV, the simulation of the laminate build-up using the filament winding process is the key factor. Modelling up to 60 individual layers allows an evaluation of potentially critical stresses along the entire fiber path. Small design changes might have a huge impact on ultimate performance of the CPV. For durability, the focus is on the area where different materials of liner, composite and boss meet (“triple point”). Once the laminate design is optimized, the motion program for the CNC filament winding machine can be generated accordingly.
Numerical modelling is the bases for designing, simulating and manufacturing efficient CPV’s. For the past years, significant progress has been made to understand the behavior of such tanks and the seamless interface between different simulation and production has drastically reduced the development time and costs of CPV’s. However, the final validation and certification program are still based on experimental (destructive) testing.