Axon Automotive's structure uses Axontex technology to manufacture very lightweight composite structural beams with high strength and stiffness.
Axon Automotive's structure uses Axontex technology to manufacture very lightweight composite structural beams with high strength and stiffness.


Part 1
of this article looked at the selection of materials for automotive applications. In Part 2 we investigate the use of carbon fibre and the importance of recycling.
 

Carbon fibre

Increased competition from corporate changes and faster curing cycles are likely to encourage more automotive designers to use reinforced polymers. Parts integration has being going on for many years. As Axon Automotive has been demonstrating, a lot more could be done in this area.

UK company Axon has developed a city car, a ‘B’ size car with dimensions very close to a Citroen C1 but with a complete body frame weighing it claims only 50 kg.

Demands for lighter cars which minimise fuel use and emissions encouraged the company to develop its ‘body in black’ (BiB) carbon fibre composite system which it says weighs 50 kg for a city car to 80 kg for a medium saloon car. Axon also says that ways to produce affordable platforms quickly, and with modest initial volumes that can be grown with demand, have great potential.

“With structures that are much more integrated you have fewer parts to make,” explains Steve Cousins, Managing Director, Axon Automotive.

Cousins says that in a classic body in white there are 350 parts but that as there are fewer parts in his company’s BiB it is a lot quicker to make the structure. According to Cousins a large part such as a 3 m high beam would only require a 10 minute infusion time.

Axon’s structure uses Axontex technology to manufacture very light weight composite structural beams with high strength and stiffness. According to the company the system “provides all the stiffness and crash compliance yet allows external body panels of any desired material, from steel to thermoplastics and everything in between.” It adds that a “new carbon fibre composite resin system Crestapol 1250 LV was developed with Scott Bader and was used on the city car frame to give lower cost and greater toughness.”

Carbon fibre is also being used by Ford, which is partnering with Dow Automotive Systems to research the use of advanced carbon fibre composites in high-volume vehicles. Cutting the weight of new cars and trucks by up to 750 lbs by the end of the decade is a key component of Ford’s strategy to improve fuel efficiency. (See Ford and Dow team up on low cost, high volume carbon fibre composites.)

“There are two ways to reduce energy use in vehicles,” explains Paul Mascarenas, Ford chief technical officer and vice president, Research and Innovation. They are “improving the conversion efficiency of fuels to motion and reducing the amount of work that powertrains need to do.”

Ford is investigating a range of new materials, enhanced design processes and new manufacturing techniques that would enable automotive structures to meet increasingly stringent safety and quality standards while cutting weight.
Paul Mascarenas, Ford chief technical officer and vice president, Research and Innovation

“Ford is tackling the conversion problem primarily through downsizing engines with EcoBoost and electrification while mass reduction and improved aerodynamics are keys to reducing the workload,” he explains.

“Ford is investigating a range of new materials, enhanced design processes and new manufacturing techniques that would enable automotive structures to meet increasingly stringent safety and quality standards while cutting weight.”

“This partnership with Ford on carbon fibre composites is a logical next step to progress already achieved through the use of lightweight, high-strength polymers and structural bonding technology,” adds Florian Schattenmann, Director of Research and Development for Dow Automotive Systems.

Dow Automotive and Ford have signed a joint development agreement that will see researchers from the two companies ­collaborate in several areas. The development teams will focus on establishing an economical source of automotive-grade carbon fibre and develop component manufacturing methods for high-volume automotive applications. The partnership will seek to combine the best of Ford’s capabilities and experience in design, ­engineering and ­high-volume vehicle production with Dow Automotive’s strengths in R&D, materials science and high-volume polymer processing.

The joint development effort will also leverage work that The Dow Chemical Company has already begun through ­partnerships with Turkish carbon fibre manufacturer AKSA and the US Department of Energy’s Oak Ridge National Laboratory (ORNL). (See Dow and AKSA form carbon fibre joint venture in Turkey.)

If the joint development effort is successful, carbon fibre components may begin appearing on new Ford vehicles in the latter part of this decade as product development teams work toward meeting new fuel efficiency standards of more than 50 mpg and extending the range of plug-in vehicles.

Recycling

Designers are currently spoilt for choice when selecting the appropriate polymer and reinforcing material. However Nigel Keen, Business Support Engineer at the National Composites Centre in Bristol, UK, says that “speed of process is the important factor currently favouring thermoplastics rather than recyclability, as there are now EU compliant solutions for recycling both thermoplastic and thermosets.”

Recycling is still an issue though that car makers have to consider when deciding on the design of components. 100% recycling can it is claimed be achieved with thermosets. Bruce Ogilvy, Manager, Sales and Marketing Department, Eco-Wolf Inc, claims that the company’s recycling system will become ­increasingly popular as pressure to ­demonstrate that a viable means exists for recycling components made from thermosets.

“As the cost of materials continues to rise and regulations dealing with landfills grow the ability to reincorporate what was formerly a waste product becomes an increasingly attractive option,” says Ogilvy.

“While the cash savings of replacing a percentage of virgin material with recycled material does not seem great at first when the savings of landfill costs and related expenses are added the savings become a major consideration. We are currently working with companies to set up fibre recycling plants to handle not only fibreglass products but carbon fibre composites.”

The Eco-Wolf recycling system consists of two major components. The Eco-Grinder, which is robustly constructed and specifically designed to withstand the abrasive nature of the material while maintaining the integrity of the glass or natural fibres. This allows the fibres to be reincorporated back into new products.

The second part of the process is the Eco-Dispensing Macerator. This component is a pneumatic powered device that meters and transports the material processed by the Eco-Grinder to the pre-existing dispensing equipment where it is injected into the resin stream upon operator demand. Eco-Wolf supplies the adapter that reincorporates the scrap without changing resin systems.

Ogilvy claims that Eco-Wolf has “developed the only method of processing carbon fibre that does not greatly reduce the tensile strength as it does not use heat to recover the carbon fibre from the resin bonding agent.” 

Ultimately the designer is likely to be forced to compromise. That is because the choice of polymer and reinforcement material is likely to be dictated to some extent by how easily the process can be automated. Also, although curing times have come down for some processes, introducing a new composite production process into a car plant is not simply a matter of sorting out all the variables including design, material, size, and cost. The effect on secondary processes such as finishing i.e. painting has to be understood. It will be interesting to see how car makers achieve the targets for future lightweight vehicles. ♦

  •  Read Part 1 of this feature here.

This article was published in the March/April 2013 issue of Reinforced Plastics magazine.

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