CarbonTT's four-axle NCF composite chassis adds 185kg of load capacity to Borco Höhns' 3.5 tonne Fiat Ducato market vehicle.
Demand for specialised, light commercial vehicles is surging in the evolving urban logistics and mobile commerce landscape. On-demand services are booming, driven by rapid urbanisation, with sectors such as last-mile delivery, food distribution, mobile healthcare and specialist maintenance increasingly relying on compact, adaptable vehicles. These vehicles can provide efficient and flexible services in densely populated and restricted areas where larger vehicles face operational and regulatory hurdles.
A key constraint for these industries is the stringent 3.5 metric tonne (MT) weight threshold - a regulation that is critical in most European markets and many global markets, distinguishing light commercial vehicles (LCVs) from heavy goods vehicles (HGVs). Exceeding this limit typically incurs additional costs (e.g. tolls), requires specialised driving licences and subjects operators to stricter regulation. Staying within the 3.5-MT classification is vital for companies striving to optimise their logistics while minimising expenses.
In 2023, specialist retail vehicle seller Borco Höhns (Rothenburg, Germany) set out to improve the commercial efficiency of its 3.5-MT maximum weight vehicles by minimising their base weight. To this end, Borco Höhns partnered with Carbon Truck & Trailer GmbH (CarbonTT, Buxtehude, Germany), which specialises in the development and automated production of structural composites, to develop a carbon fibre-reinforced polymer (CFRP) chassis to replace the steel chassis for its Fiat Ducato-based retail vehicles.
Developed over an 18-month period, the CFRP chassis reduces the weight of the sub-3.5MT Borco Höhns Fiat Ducato by 185kg, while maintaining the robustness required for specialist retail vehicle applications. This has increased the steel chassis version's 510kg payload by 36 per cent, resulting in a proportional increase in revenue potential per transport.
‘By reducing the weight of the vehicle, we offer our customers greater flexibility - whether it's to carry more goods, add equipment or comply with weight restrictions affecting permits and road access,’ explains Gerret Kalkoffen, CarbonTT CEO. ‘This could be a game changer for the entire industry.
CarbonTT designed the CFRP chassis, including optimising the fibre lay-up, resin chemistry and developing a new pultrusion manufacturing process. ‘Pultrusion manufacturing requires uniform profile thickness,’ explains Kalkoffen. ‘When the load distribution is not uniform, such as in the case of centrally located interfaces with the vehicle suspension, it is challenging to find the optimum values for load, weight and cost. Taking into account global loads, fibre costs and production speeds, we don't want to exceed 3 mm. This can only be achieved with our patented interface that transfers the load from steel to composites.
The chassis design features a symmetrical four-axis non-curled fabric (NCF) structure made from Zoltek (St. Louis, Missouri, USA) 50K tow PX35 carbon fibre, demonstrating 0°, +45°, -45° and 90° fibre orientations. ‘Stitching characteristics are key to determining the plasticity of the fabric,’ Kalkoffen notes. ‘We carefully determine seam strength and yarn type to balance the stiffness of the pultrusion process with the fabric's ability to adapt to complex shapes. This approach means precise control of the fibres during the manufacturing process, while maintaining the material's ability to handle longitudinal and torsional loads.
At the heart of the CarbonTT solution is customised pultrusion manufacturing technology. The system is based on a Pultrex/KraussMaffei (Manningtree, UK) pultrusion line with custom-designed fibre holders, moulding units, fixtures, automatic tension control systems, saws and injection boxes.CarbonTT is based on a polyurethane system from Covestro (Leverkusen, Germany), formulated with a special resin containing a variety of functional additives to facilitate the smooth running of the pultrusion process. These additives regulate the viscosity and curing kinetics to achieve complete fibre wetting during the infusion phase. In addition, UV stabilisers and heat-resistant compounds are incorporated into the resin to provide long-term durability of the chassis.
‘Our fibre guidance system represents a significant advancement in pultrusion technology,’ says Kalkoffen. ‘Traditional pultrusion technology struggles with complex fibre structures. After years and countless efforts, we have developed a unique control system that uses multiple sensors to maintain precise fibre feed positioning relative to the die. These sensors continuously monitor the position and orientation of the fibres, transmitting the data to an automated tension control system, which makes real-time adjustments to prevent fibres from misaligning, puckering or forming voids that could compromise the integrity of the structure’. This technology enables CarbonTT to produce complex shaped profiles at high speeds without wrinkles, which is essential for achieving good material properties and minimising fibre costs for each application.
CarbonTT has also developed proprietary technology to generate and control pressure gradients in the injection zone. ‘Generating sufficient pressure in an injection moulding system requires precise control of multiple variables,’ notes Kalkoffen. ‘Due to the continuous nature of the pultrusion process, the sides of the injection box are open, so if a certain amount of pressure is required to get the resin to the centre fibre, you can't just increase the pressure on the metering machine. We had to develop the resin to penetrate and cure in this challenging situation.
Vehicle-level kinetic validation was then performed. This involved dedicated testing using fully instrumented vehicles and test tracks to collect stability performance data, including emergency manoeuvre scenarios to validate the impact of the composite chassis. Each stage was subjected to a certification process by TÜV Rhineland (Cologne), the German vehicle certification body, to ensure compliance with industry standards.
This completed CFRP beam component demonstrates the four-axial fabric structure and the optimised stiffness-to-weight ratio achieved through the CarbonTT pultrusion process.
With the continued expansion of urban distribution and mobile retailing, as well as increased pressure to reduce emissions, lightweight solutions will play a vital role in the development of the 3.5 metric tonne vehicle industry. Significant increases in payload, the ability to achieve higher revenues with fewer journeys and advancing sustainability metrics suggest that composite chassis technology is likely to become increasingly prevalent in future commercial vehicle applications.