Natural fibre composites vs carbon fibres: Engineering lighter cars

Natural composites make lightweight cars lighter Natural fibres offer benefits against carbon fibre and offer a green composite benefit
A UK funded project is aiming to develop automotive structures using flax fibres and a bio-epoxy resin intermingled with carbon fibres. The project called CARBIO, is developing hybrid composite materials to produce lighter, cheaper, and environmentally sound parts.

Compared to carbon fibres, flax materials are renewable, lower in cost to produce, are CO2 neutral and have excellent vibration damping properties. In addition, bio-epoxy resins based on cashew nut shell liquids (CNSL) offer enhanced toughness, noise damping and further sustainability benefits over synthetic epoxies.

By creating a hybrid structure using the flax and bio-epoxy to replace some of the carbon fibres, enhanced properties such as lower weight, cost, NVH and environmental impact can be gained. A 50/50 carbon and flax fibre hybrid biocomposite has been made from Biotex Flax supplied by Composites Evolution and prepregged by SHD Composite Materials. It shows equal bending stiffness to carbon fibre while providing a 15% cost saving, 7% weight reduction and 58% more vibration damping.

Composites Evolution has developed a range of carbon flax hybrid materials to support the growing trend, and its materials have proven a lower cost alternative to carbon fibre for numerous applications.

Brendon Weager, technical director at Composites Evolution, says: “We have developed these hybrid materials working alongside automotive OEMs and sporting goods manufacturers to meet their increasing demands for cost reduction, performance, and sustainability. We fully expect to see carbon flax hybrid structures playing their part in the next generation of vehicles and sports products.”

The materials propose three ways of harnessing the benefits of flax within carbon fibre composites – hybrid woven yarn fabrics, hybrid spread tow fabrics and a layered hybrid approach. In the layered hybrid approach, one or more layers of carbon fibre are replaced with Composites Evolution’s Biotex Flax to create multi-layer, micro-sandwich structures with equal bending stiffness to all-carbon laminates, but with reduced cost, reduced weight and increased shock absorption.

Hybrid fabrics, composed of carbon and flax yarns, offer an alternative approach, where the carbon and flax can work synergistically to provide tunable performance and unique aesthetics.

These fabrics are particularly suitable for use in one or two layer laminates and where directional properties are required.

One example in the Biotex range is a 180g/m2 twill hybrid fabric that is aimed to suit complex structural and decorative parts. Hybrid carbon flax spread tow fabrics are also possible, offering superior properties due to the high degree of fibre alignment and low crimp.

Gareth Davies, Composites Evolution’s sales manager says: “There is a growing impetus for the use of natural, lightweight, plastics in the automotive sector. The adoption of carbon fibre-epoxy composites to reduce vehicle weight is presenting significant challenges with regards to the volumes needed in the automotive industry.

“[These are] important results that demonstrate the value that biocomposites, and specifically flax, can add to the automotive sector.”

Author
Justin Cunningham

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Do you have any comments about this article?
may we use coconut fibres/coir for these composite materials?

Comment daljeet singh, 26/04/2017
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