As the UK focuses on its first all-electric bus city in Coventry, composite materials are playing a vital role in optimising vehicle performance, minimising weight and maximising fuel efficiency. Patrick Loock, European sales director at Exel Composites, discusses the expanding e-bus market, the growing use of composite materials in these vehicles and the benefits they bring.
Exel composites
Government policies and investments are speeding up the evolution of zero-emission public transport. In October 2024, the UK announced a £500 million investment to introduce 1,200 domestically manufactured zero-emission buses over three years. This includes the creation of a UK bus manufacturing expert panel to promote zero-emission technologies. Composite materials are crucial in meeting this demand, enhancing durability, improving mechanical properties like stiffness and tensile strength and supporting the overall performance and sustainability of zero-emission buses.
Financial incentives, such as the £2 single-fare cap introduced in 2023, have propelled the use of public transport, with England alone witnessing a 7% increase in bus use between March 2023 and 2024. Continued government support will be key to ensuring this trend is sustained.
The impact of composite materials on e-bus design
Early electric buses performed poorly as far as range was concerned, only offering 90 - 150 km per charge, while diesel buses ran for 575 km. However, advancements in battery technology, including energy density and charging speed, along with innovations in materials like composites, have improved operational efficiency. In September 2023, VDL Bus & Coach’s new-generation electric ‘Citea’ travelled 310 miles in 24 hours in the “MaxiMile Challenge”.
Composites play a crucial role in the construction of modern electric buses, where they are roofs, body panels, side walls, skirt profiles and luggage racks. They offer superior durability and performance versus traditional materials like steel and aluminium.
They can provide up to three times the tensile strength per unit weight, have low thermal conductivity and a coefficient of thermal expansion of 0.1 – 0.5 x 10-6/°C, ensuring minimal dimensional change.
The ability to mould composites into complex shapes makes them ideal for bus construction. Advanced manufacturing techniques like pultrusion and continuous lamination allow to produce seamless parts. For example, composite side panel assembly is simplified by eliminating the need to join multiple metal panels.
Weight reduction plays a crucial role in e-bus design, as battery packs alone can add 1,350 – 2,300 kg to the weight of a vehicle. Composites are key to achieving this without compromising strength and resilience.
For instance, fibreglass strikes a balance between durability, lifespan and structural integrity, with some products offering up to 20% weight reduction compared to aluminium. Carbon fibre, with up to 40% weight reduction, is preferred for load-bearing applications, though it comes at a premium.
Hybrid composites with different types of fibre offer a cost-effective alternative, reducing weight by 20% to 40% while providing aluminium-like stiffness.
Corrosion resistance and life cycle cost benefits of composites
Aside from weight savings, composite materials are extremely corrosion-resistant compared to metals. Unlike steel, which requires coatings like hot-dip galvanising, they eliminate the need for these treatments, reducing production costs. They are ideal for public transport, where longevity and affordability are essential, and reduce maintenance and downtime, thus improving service availability.
Composites used in electric bus manufacturing improve efficiency, extend the lifespan of vehicles and facilitate sustainability. As demand for zero-emission public transport grows, t