RWTH Aachen Explores Hybrid Filament Winding for Hydrogen Pressure Vessels

Updated on May 25, 2026 • 6 min read

Researchers at RWTH Aachen University’s Institut für Textiltechnik (ITA) are investigating a new filament winding strategy aimed at reducing the cost and complexity of composite pressure vessels (CPVs) used for hydrogen storage.

The work focuses on targeted reinforcement of the dome region in high-pressure hydrogen tanks — one of the most technically demanding and material-intensive areas of the vessel.

Why dome reinforcement matters

Composite pressure vessels used in hydrogen fuel systems rely heavily on carbon fiber overwraps for strength.

According to the research, the composite overwrap accounts for roughly:

• 57–67% of total vessel cost

depending on storage pressure.

The challenge comes from the stress distribution inside cylindrical pressure vessels.

Pressure vessel stress behavior

Region	Stress Characteristic
Cylinder wall	Hoop stress dominates
Dome area	Complex multi-directional stress
Axial direction	Lower than hoop stress

The dome regions require localized reinforcement because stress concentrations differ from the cylindrical body.

Previous dome reinforcement approaches

Earlier approaches attempted to strengthen dome regions using additional carbon fiber patches or inserts.

DOE “doily” concept

A 2013 U.S. Department of Energy design study proposed:

• discrete carbon fiber reinforcement strips
• placed in the dome before winding

These “doilies” improved reinforcement efficiency but introduced manufacturing complexity.

By 2015, the DOE reportedly removed the concept from baseline production strategies because:

• extra process steps slowed manufacturing
• automation became more difficult
• high-volume scalability was uncertain

Industry solutions already explored

Several companies have since revisited local dome reinforcement.

Cevotec fiber patch placement

Cevotec developed a system that places oriented fiber patches onto the liner dome before filament winding.

Advantages include:

• precise reinforcement orientation
• localized material placement
• reduced unnecessary overwrap

However, it still requires:

• separate placement operations
• additional handling steps
• dedicated fiber patch processing

Taniq integrated robotic cell

Taniq combines:

• automated fiber placement
• filament winding
• rubber winding

within a robotic manufacturing cell.

This allows local reinforcement during the laminate build sequence but still adds process complexity.

RWTH Aachen’s different approach

ITA researchers are attempting to solve the problem using only filament winding itself.

Their concept uses what they call a:

“Hybrid layer”

Unlike standard winding paths:

• hoop layers stay in cylindrical regions
• polar layers terminate in domes
• helical layers connect broader vessel sections

the hybrid layer uses:

• one endpoint in the dome
• one endpoint in the cylinder

This creates localized dome reinforcement without separate patch placement systems.

Why towpregs are important

The method depends on towpreg materials.

Towpregs combine:

• reinforcement fiber
• partially cured resin

into one intermediate product.

Because the resin remains tacky during winding, the fibers can follow:

• non-geodesic trajectories
• unconventional winding paths
• locally reinforced routes

that would normally slip during conventional wet winding.

Manufacturing advantages

The approach could provide several industrial benefits.

Potential advantages of hybrid winding

Benefit	Why It Matters
No machine change	Faster production
No fiber cutting	Reduced process interruption
No transfer operation	Better automation
Integrated reinforcement	Simpler manufacturing flow
Lower material use	Reduced vessel cost

For hydrogen tank manufacturing, these advantages are significant because production speed and fiber efficiency strongly influence final tank economics.

Technical challenges still remain

The concept has already been demonstrated at laboratory scale, but engineering challenges remain unresolved.

1. Local thickness buildup

Multiple hybrid layers can create excessive material accumulation near cylinder endpoints.

Researchers may need to:

• stagger layer endpoints
• optimize transition geometry
• redistribute laminate buildup

to avoid structural weaknesses.

2. Fiber instability and slippage

Reducing reinforcement distance saves material, but shorter transitions increase the risk of:

• fiber instability
• tow slippage
• winding defects

Critical parameters include:

• winding tension
• tow bandwidth
• vessel diameter
• trajectory angle

Finite element simulation becomes essential

The next phase will use advanced finite element modeling.

The project uses:

• RHWind software from Rheinmetall Invent
• progressive damage simulation
• manufacturable laminate geometry export

through the publicly funded H2Lorica project.

The simulations aim to determine:

• whether hybrid layers can replace some helical layers
• how much carbon fiber can be saved
• how reinforcement affects failure behavior
• optimal endpoint positioning strategies

Why this research matters for hydrogen infrastructure

Hydrogen storage remains one of the biggest cost barriers in fuel cell transportation and hydrogen logistics.

Large Type IV pressure vessels are widely used in:

• hydrogen trucks
• buses
• fuel cell vehicles
• MEGC transport systems
• hydrogen refueling stations

Reducing carbon fiber consumption while maintaining safety could significantly improve hydrogen economics.

Since carbon fiber remains one of the most expensive components in pressure vessel manufacturing, even modest material savings could scale into major industrial cost reductions.

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Editorial Perspective

This research is important because it attacks one of the least discussed problems in hydrogen infrastructure:

manufacturing efficiency inside composite pressure vessel production.

Most hydrogen discussions focus on electrolyzers, fuel cells or hydrogen prices. But composite tank manufacturing is equally critical.

RWTH Aachen’s hybrid winding concept is especially interesting because it does not rely on adding more automation hardware. Instead, it tries to extract more performance directly from the winding process itself.

If successful, the approach could help manufacturers:

• reduce carbon fiber waste
• simplify production lines
• improve scalability
• lower vessel cost

all without introducing separate reinforcement stations or complex handling systems.

For the hydrogen economy, that kind of manufacturing simplification may become just as important as advances in hydrogen generation itself.