High-volume composite braiding and circular design in structural applications

For all their well-documented advantages - high specific strength, stiffness and corrosion resistance – composites have historically struggled to achieve two things at once: true high-volume manufacture and credible sustainability

According to Sam Donegani, operations manager at Composite Braiding, those twin challenges are precisely why the company exists. “As a business, we really have two main reasons for being,” he explains. “High volume and sustainability in composites.”

UNLOCKING VOLUME THROUGH BRAIDING

The barrier to volume production has long constrained wider adoption of composites, particularly in automotive, infrastructure and transport. Traditional composite processes often rely on labour-intensive layup or slow curing cycles, demanding either “a small army of people or some very, very expensive kit,” as Donegani puts it.

Composite Braiding’s core process addresses this bottleneck directly. Using industrial braiding machines, the company produces continuous tubular preforms, or flexible composite “socks”, at exceptional speed. “One small braiding machine can produce about a mile of this a day,” Donegani says. “And that machine can be run by one person.” The implication for scalability is significant: fibre architecture can be created continuously, repeatably and with minimal labour input.

These braided preforms are subsequently consolidated into fully structural components using heat and pressure. The company specialises in hollow structural parts, from small, high-performance components for drones and bicycles through to large-scale railway and bridge structures. However, producing the preform is only half the challenge; the second is moulding it fast enough to support volume manufacture.

Historically, moulding high-performance composite parts has involved long cycle times. Composite Braiding has developed proprietary processes that compress moulding cycles from hours down to minutes. “We can mould something that would historically have taken several hours in just a couple of minutes,” Donegani notes, making high-throughput production viable.

ENERGY EFFICIENT PROCESSING

Volume alone is not enough if it comes at an environmental cost. Composites have traditionally delivered sustainability benefits through lightweighting, but concerns remain around embedded carbon and end-of-life disposal. Composite Braiding’s approach centres on blended thermoplastic composites, where reinforcement fibres and thermoplastic matrix fibres are integrated from the outset.

Examples include carbon fibre with PPS, glass fibre with polypropylene, and glass fibre with nylon 6. These materials offer relatively low embodied CO2 and, critically, eliminate many energy- and waste-intensive steps associated with thermoset composites. “There’s no laminating, no resin infusion, no vacuum bagging, no water phase,” Donegani explains. “To make this into a structural part, we just need heat and pressure.”

Equally important is how that heat is applied. Conventional oven-based moulding heats large air volumes and massive tooling structures to reach process temperature, which is an inherently inefficient approach. Composite Braiding has instead developed tooling that localises heat to the mould surface only. “The mould face is at about 280°C, and the rest of the structure never gets above room temperature,” says Donegani. The result is a claimed 97–98% reduction in processing energy compared with oven-based systems.

DESIGNING FOR COMPLEXITY AND PERFORMANCE

Alongside process development, the company has invested heavily in materials and design capability to support complex geometries.

One example is an automotive A-pillar reinforcement originally designed in aluminium. The OEM found the geometry technically and economically unviable in metal and turned to Composite Braiding. The final solution - a single-piece braided and moulded composite - was produced from a simple cylindrical braid, with all geometric complexity introduced during moulding. “That was made in a single piece,” Donegani says, “just by braiding a big cylinder and using a novel mould.”

The process also enables internal reinforcement features to be moulded integrally within hollow sections, opening up new opportunities for load path optimisation. Fibre orientation can be tuned continuously: 0° fibres for axial stiffness, ±45° for torsion, or near-90° for crush resistance. “That gives us a vast degree of tunability,” Donegani notes, allowing engineers to tailor performance while minimising material usage.

CIRCULARITY BY DESIGN

Thermoplastic composites also fundamentally change the end-of-life equation. Unlike thermosets, they can be remelted, reshaped or reprocessed. “If it’s just cosmetic damage, I can put it back in the mould tool it came out of and make it back into the same part,” Donegani explains. Fibres can also be recovered by melting out the matrix.

However, true circularity extends beyond materials to assemblies. Composite Braiding has demonstrated fully mono-material structures such as beams, closure panels and even fasteners made from the same carbon fibre/PA6 composite. This eliminates dissimilar materials, adhesives and galvanic corrosion risks, while simplifying recycling. “At end of life, you haven’t got a bunch of different materials to deal with,” says Donegani.

The company has even developed composite rivets with high pull-out strength that can be installed and removed in seconds, enabling straightforward disassembly. “We’ve designed for disassembly as well,” he adds.

Braiding also addresses another long-standing issue in composites: production waste. Traditional prepreg-based processes can generate 30–40% scrap. Continuous braiding reduces this to around 1%, limited mainly to start- and end-of-run material—and that waste is reusable. Composite Braiding routinely compression-moulds offcuts into secondary products such as grab poles or panels, closing the loop further. “We put our 30–40% waste figure down to about 1%,” Donegani says. “And that 1% is all reusable as well.”

FROM AUTOMOTIVE TO RAIL

The culmination of these capabilities is visible in large-scale infrastructure projects, such as a cantilevered twin-track railway structure developed under a Connected Places Catapult programme. Measuring around eight metres tall with a 4.7-metre cantilever, the composite structure delivered a 44% weight reduction compared with steel. Reduced mass lowers transport, lifting, access road construction and possession-time costs, amplifying the value of lightweighting far beyond the component itself. The project has been described by a Tier 1 rail contractor as a “game changer.”

A SCALABLE PATH FORWARD

Taken together, high-speed braiding, energy-efficient thermoplastic processing and circular design principles point toward a more scalable and sustainable future for composites. As Donegani concludes, the challenge is no longer whether composites can deliver performance, but whether they can do so “at high volume, sustainably, and in the shapes that engineers actually need.”