Composite pressure vessels are the key storage system for hydrogen-powered mobility. Maintaining high pressure of up to 700 bars, the cylindrical tanks store the hydrogen used in fuel cell-powered electric vehicles like trucks, busses, trains and passenger cars. The main cost driver of the tanks is the carbon fiber material itself, representing over 50% of the total cost. Automation specialist Cevotec has developed an industrial solution that, in combination with the established filament winding process, improves the material efficiency and reduces the weight of a tank by 15% while achieving equivalent mechanical properties.

Key element of the solution is the automated, precise lay-up of carbon fiber reinforcements directly on the liner, using Cevotec’s Fiber Patch Placement (FPP) technology. Customized patches of fiber material are placed on the domes down to the equator region, which is the cylinder-to-dome transition, to locally reinforce these areas.

The reinforcements replace high-angle helical layers (HAHL) in the filament winding process. The primary role of the HAHL is to reinforce the critical equator region of the vessel. The dome reinforcements substitute the HAHL function, and they don’t span across the cylindrical portion of the vessel. This translates into a considerable saving of material in the hoop area which contributes only marginally to the mechanical performance. In addition, the reinforcements also facilitate a smoother stiffness transition between the cylinder and dome sections, leading to a further optimized laminate design.

To optimally support the combination of filament winding process and FPP technology, Cevotec has conceptualized SAMBA PV, the automated fiber lay-up system dedicated to the specific requirements of pressure vessels. The production system applies the fiber material in an independent process, parallel to the filament winding, and therefore the total cycle time of a vessel is shortened.

The design of the reinforcements as well as the programming of the production robots can be adjusted to different types of pressure vessels in an integrated digital process with the CAD-CAM software ARTIST STUDIO. During production, the SAMBA PV system first applies the reinforcement on the liner, then the reinforced liner is transferred to an adjusted filament winding process without the high-angle helical layers. Net on net, approximately 15% less material is needed to achieve identical stress ratios. This also translates into 15% less weight of the tank and effectively boosts capacities of existing winding stations by up to 20%.

The combined benefits of implementing the dome reinforcement solution allow manufacturers to produce more vessels at lower cost. The necessary additional investment pays back already in the first year of production and thus represents a very attractive investment opportunity.

About Cevotec:

Munich-based automation specialist Cevotec offers one of the world’s most advanced production systems for complex fiber composites. At the intersection of composites, mechanical engineering and software, Cevotec develops production systems and software based on Fiber Patch Placement (FPP) technology: SAMBA and ARTIST STUDIO. The systems, which are particularly suited for automated fiber placement on complex 3D geometries, process carbon fibers, glass fibers, adhesive films and other technical fibers. They can be used for a broad range of applications. Such flexibility is particularly appreciated by customers from aerospace and med-tech industries, who realize cost and time savings of 20%-60% when switching from manual processes to FPP.

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