Problem/issue being addressed
CNG (Compressed Natural Gas) tanks are used in 1.3 million vehicles in Europe (24 million worldwide) and are typically made from a metal or polymer liner, over-wound with a carbon/epoxy thermoset composite. However, carbon/epoxy composites are not ideal. This wet winding process results in inconsistencies in the epoxy matrix and misalignment of the carbon fibre, giving up to 10% variation in tank burst pressure. More material is therefore added to compensate, increasing cost and weight, and the process is slow.
One alternative is to manufacture carbon/polyamide thermoplastic tapes, and subsequently heat and apply them to the liner in a high-speed winding process. This process has the potential to overcome the variation in wet-wound epoxies, but material manufacturers have not previously been able to make tapes of high enough quality, and vessel manufacturers have not been able to wind them efficiently.
To overcome this problem, Coventive Composites has developed an improved impregnation process to make carbon/polyamide tape with lower voids and less variability in performance. In parallel, MFTech has developed a robotic winding process to double production speed, so that Plastic Omnium can efficiently manufacture CNG tanks with carbon/polyamide thermoplastic tapes.
This new thermoplastic tape, robotic equipment and winding process allows the production of higher quality pressure vessels, reducing variation in tank burst pressure. This enables less material to be used, saving both cost and weight. Plastic Omnium’s testing has shown that these pressure vessels can meet (and exceed) the targets set by their customers, reducing weight by 10% and reducing cost by 20%.
Why is it important for society?
By developing a new generation of CNG tanks, this project supports the aim of the European Alternative Fuels Strategy:
• Reduce oil dependence
• Reduce GHG emissions
• Improve the air quality
• Enhance the competitiveness of European industry
The strategy document established a coherent policy on alternative fuels. CNG forms an integral part of this strategy.
Overall objectives
The tape, winding process and pressure vessels have so far been demonstrated on a prototype scale, and the specific objectives of this project address 3 key barriers to commercialisation:
• Optimise and upscale the tape process to meet cost, processability and property requirements.
• Enhance the vessel-winding process to meet performance, weight and productivity needs.
• Upscale the manufacture of carbon/polyamide CNG tanks, to enable economic production.
This project will advance the development to TRL 8, meeting customers’ cost and weight targets.
Conclusion of the action
By the end of the final period, the key results can be summarised as follows:
1. Refined formulations of the thermoplastic tapes, which have been validated through the production and testing of CNG tanks manufactured by MFTech and tested by Plastic Omnium.
2. The development and implementation of an upscaled tape production process by Coventive Composites that is capable of manufacturing the PA6-carbon fibre tapes with the required quality and production volumes to support post-project exploitation.
3. The development and implementation of an upscaled CNG tank production process by MFTech, which is capable of manufacturing the thermoplastic tanks at the required rate and quality to meet the commercial requirements of Plastic Omnium.
4. The preparation of a robust business plan to support the post-project commercialisation needs of the project partners.
