Banking on Composites

Lotus Engineering plc believes tougher pedestrian-impact rules that take effect in Europe in 2010 will help it sell technology for composite front-end structures, but during 2005, composites will remain a hard sell.

“For mainstream companies, it is true” that they are being very conservative about material choices, says Jason Rowe, chief material engineer for Lotus Engineering, the British subsidiary of Malaysia's Perusahaan Otomobil Nasional Bhd. (Proton).

“Their engineers are steeped in metal.”

At the JEC Automotive Forum composite industry exhibition in Paris, managers from Lotus and other companies say composites are not gaining much ground against steel right now, both for technical reasons and because the current competitive global climate does not encourage taking risks.

Lotus shows the Ecolite front-end structure it is developing with Germany's Jacob Composite that uses new thermoforming and joining techniques Lotus expects will make composites competitive up to volumes of 30,000 units per year, from 10,000 units annually at present.

Composites absorb crash impacts by disintegrating, while metal has to fold itself up. Thus, says Rowe, a composite front end will provide the same crash protection in less space than a steel one. That gives developers more room to add pedestrian impact measures.

At the same time, he says, in a lower-medium car, such as the Volkswagen Golf or Ford Focus, the structure would weigh 30% less than steel.

Lotus and Jacob intend to have a validated composite front end ready by October, after which time they will begin engineering an entire composite structure.

Lotus already has developed composite structures with glass- or carbon-fiber reinforcement, using resin transfer molding, but until now a slow cycle time has made them reasonable only for cars produced in annual volumes of 10,000 units or less.

The project with Jacob will develop reinforced thermoplastic components, “based on a range of polyamide, PBT and polystyrene resin systems,” according to the company.

Lotus intends to match the crash protection of a steel front end that gains five stars in EuroNCAP tests, while providing an 80% improvement in residual crush length, 30% weight savings, 50% tool savings and a business case for 30,000 units annually.

At the same time that Lotus is trying to win business for composites on structures, the material is losing applications in body panels. The Renault Espace and the rear hatch on the Mercedes-Benz A-Class have switched from composites to steel, and General Motors Corp.'s Saturn brand is doing the same for the body panels on its cars.

At the JEC Automotive Forum, Hamid Kia, GM's top scientist for sheet molding compound (SMC), says the auto maker has banned SMC body panels at paint shops that are changing over to a powder primer because of a reaction called “popping,” in which tiny holes develop in the paint surface.

GM conducted a series of experiments to discover the cause, which turned out to be a commonly used additive in SMC mixtures, called Neulon T-plus.

Because of the additive, atmospheric gases are absorbed into the SMC while it is waiting to be painted, and they become bubbles during the oven phase when the powder primer melts.

In March, Kia called North American suppliers of SMC to a meeting and challenged them to come up with a new additive that will permit SMC panels to be stockpiled as long as 48 hours and then painted perfectly.

Mercedes is switching to steel on the new-generation A-Class because it anticipates higher volumes, which makes the metal a better business case than composites.

But Karl-Heinz Kalmbach, automotive product manager for Swiss supplier Quadrant Plastics Composites AG, which provided the SMC for the first-generation A-Class hatch, tells the Automotive Forum that early problems encountered in producing the composite hatch have been resolved.

Several other presentations at the Automotive Forum tackle the subject of improving the penetration of composites in the auto industry.

Ashland Chemical Co. is developing a bonding process that would help solve the problem of achieving higher production volumes with composites.

By mixing nanoparticles of ferrite or iron oxide in an epoxy resin, the resin, itself, develops the heat required to set when it is treated with microwaves.

This process will speed up bonding of composite parts from three or four minutes now to one minute, says Hartwig Lohse, European technical manager for Ashland.

Preliminary studies make a positive business case for a composite deck lid at volumes of 120,000 per year, he says.

However, the technology will remain in the development stage for another 18-24 months, he says, adding, “and you never know what kind of surprises we will see in the future on larger parts.”

Another technology in development is a new additive from BYK-Chemie GmbH, BYK-P 9080.

Gerard Reestman, technical service manager for closed-mold processes at the company, says adding 9080 to a compound for making exterior body panels from SMC improves the material flow in the mold, paint adhesion, bonding and surface quality.

He says BMW AG and other auto makers are testing the additive now, which could lead to approval by the end of the year.

While facing stiff challenges, composite materials are not out. Their light weight, corrosion resistance and low tooling costs are significant attributes.

Quadrant continues to supply SMC for three composite hatches in production: the Nissan Murano, Stagea and Infiniti FX. Nissan Motor Co. Ltd. estimates the 51-lb. (23-kg) Murano hatch weighs 17% less than a steel hatch.

And the JEC innovation of the year in the ground transportation category was a composite underbody panel for DaimlerChrysler AG made with polypropylene thermoplastic reinforced with abaca, a natural fiber from the Musa textiles banana shrub.

DC patented the system, Reiter Automotive Systems industrialized it and Manila Cordage of the Philippines provides the fibers, which are roughly 5 to 9 ft. (1.5 to 2.7 m) long.

The process was picked because using natural fibers contributes to sustainable development.