SHAPE FORMING
composite material rather than aluminium. A lighter battery box has a positive knock-on effect on the entire vehicle. With a lighter vehicle weight, smaller batteries (or reduced engine sizes for hybrids) are required to haul the vehicle. This positive spiral results in reduced vehicle cost and range anxiety, which will play a big role in the mass adoption of EVs.
INSULATION Aside from being a lighter material in their own right, composites take away the need for a separate insulation system, which reduces weight even further, as well as helping to streamline the supply and value chain. With metal battery enclosures, an added insulation system around the material is required to keep the batteries in operational temperatures. Due to the insulating properties of composites, these materials already do a good job of preventing heat transfer, without the need to add more weight- increasing parts in the system.
NVH While not a safety-critical factor, a quieter vehicle is a more commercially viable vehicle. NVH is the result of vibration or noise, which is transmitted and radiated acoustically in the cabin. NVH is less with composites than with metals, as the former have inherent damping properties. This is true for the battery enclosures as well as other vehicle parts and could mean the difference between a luxury driving experience and a less comfortable one.
SAFETY Looking at the wider vehicle, composite battery casing can be designed as part of the vehicle
Carbon fibre profiles
body structure, not only protecting the battery, but also the passengers of the vehicle. The strength and stiffness properties of composites outweigh those of aluminium or steel, providing better crash safety. This integration will require close collaboration between the battery enclosure suppliers and chassis designers, but offers a real possibility to boost vehicle safety.
PULTRUSION High-volume production is essential in reducing overall costs. It is possible to use continuous manufacturing methods such as pultrusion to produce EV battery box components. Pultrusion as a process enables composite manufacturers to pack in more fibres in the same cross section, compared with other
composite manufacturing methods, allowing stronger, but lighter parts to be made. Remember, the fibres are the part
that carries the load in the material. Working closely with the composite manufacturer allows designers to precisely engineer the fibre content and alignments to achieve the best possible strength and weight properties at the best price point.
WHAT’S NEXT? If OEMs are going to reap the energy economy returns of light- weighting that the EPA predicted, composites will no doubt play their role. This could be a much bigger role than simply reducing the mass of the vehicle, but also improving crash safety, driving dynamics and experience as well as overall strength of the vehicle. Range anxiety remains one of the key hurdles that the EV sector must overcome, and thinking outside of the conventional material choices for battery enclosures are essential steps to reducing vehicle weight and reaping fuel economy returns. ●
Parts made by pultrusion
The author is Jari Sopanen, transportation segment owner at Exel Composites,
www.exelcomposites.com
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