Leading suppliers of plastic systems increasingly favor hybrid modules using steel or aluminum instead of the all-plastic modules that were once thought to be the answer to many engineering problems.
But suppliers also say new plastics technologies will rapidly increase the functionality and strength of hybrid modules, and further extend the applications of plastics in the car over the next two or three years.
The new confidence in hybrid technology is illustrated by Lear Corporation. The US supplier is working on a plastic door module incorporating not only plastic window guides and a plastic winding gear mechanism - but also a steel protection beam and other metal fittings.
'We combine part of the door structure with the cover of the inner door sheet,' said Fritz Schweindl, product manager for door systems at Lear, in Eberberg, Germany. 'The manufacturer then only has to produce the outer door frame and skin. It's a good example of applying hybrid technology for a module. Just plastics on their own won't allow us to fulfil the structural requirements of such complicated modules.' Schweindl believes it will take two more years before such modules are applied to production cars.
Leo van der Heiden, manager OEM business development at GE Plastics in Holland, said new plastics technologies are being developed all the time.
'Engineering plastics are constantly being improved, for such reasons as better heat stability,' he said. 'We are working hard on reducing volatiles like smell, physical properties and staining.'
And it is the suppliers who are increasingly developing these new innovations.
Jean-Louis Vaysse, Plastic Omnium's corporate research and innovation director, said: 'They result from innovative proposals by materials suppliers or module suppliers - they can also be initiated by the needs of an OEM.
'But more and more,' he said, 'the supplier has to be on top of the wave of innovation, proposing solutions at the right time to the OEM. In that respect, plastics offer new opportunities to develop more effective modules, because their disadvantages - like wider gaps - are compensated by many other off-structure advantages.
Vaysee said modules tended to be all-plastic some two or three years ago.
'Now we understand the broader technology of integrating aluminum or steel as well as certain components into larger modules,' he said.
Plastic Omnium recently created the Omnium System Car (Oscar) to demonstrate module applications. It proposed a complete plastic front-end module with integrated steel bumper beams, and also included lighting and cooling systems as state of the art applications. The company says it will be seen in production in two years' time.
'When manufacturers decided to develop commonality of non-visible platforms, it offered more opportunities for new visible plastic modules,' said Vaysse. 'These modules are easier to design and redesign, and cheaper to make. That caused a change in our responsibilities as a supplier.
'If module producers can win the confidence of the manufacturers, it eventually will allow suppliers to suggest the use of certain components to include in modules. It also transfers inbound component logistics to the module supplier.
'I believe that in the end OEMs will only make structural space frame platforms which are dressed by modules,' Vaysse said.
Manufacturers like Fiat are experimenting with new plastics modules, and plastic panels attached to a space frame platform. At the Geneva show in March, Fiat showed its Ecobasic concept car, which featured plastic body panels with molded-in color, and a complete rear hatch module making extensive use of plastics.
The one-piece tailgate had a polycarbonate back window, which Fiat claims is as clear as glass - but significantly lighter.
But Fiat says such modular technology will not appear on its production cars for some time.
'It will take some five years,' said Renzo Rosti, director of body applications at Fiat Auto. 'Before that, we'll see an increase in the amount of plastic skin applications.'
The A5,000 car based on the Ecobasic is expected to be launched in 2005.
For weight reduction, and greater stiffness, Rosti believes aluminum is still a better material for many automotive applications. 'Plastics do not offer such qualities as surface perfection and dimensional precision because they can deform. But aluminum costs much more than plastics,' he said.
The Mercedes-Benz A-class tailgate is currently the only major all-plastic module in volume production. It was developed in cooperation with GE Plastics. But many specialists think that it is too expensive to make.
'And it does not offer the structural stiffness of a tailgate with a steel inner structure,' Fiat's Rosti said.
Renault's Scenic 4x4 uses such a plastic tailgate with a steel inner fame, because it has to bear the stresses of a spare wheel.
Vaysse believes that in ten years' time front-end architecture will be different from today in both design and materials.
'Even complete front-end modules which include fenders are technically feasible,' he said. 'But that might make such a module too large to handle so it need to be assembled in pieces.'
For passive safety, plastics offer soft material benefits. Pedestrian protection from plastic front-end systems and hoods will be all-important in the next five years, with new legislation on the way.
But under-the-hood packaging may have to change. For pedestrian protection, an engine may have to sit deeper in order to allow the outer skin to absorb an impact,' said van der Heiden.
Research and development of hybrid modules is a process involving materials suppliers, module suppliers and the OEMs. But there's little doubt that the move away from all-plastic modules towards hybrid modules is not bad news for the major plastics suppliers.
Changes in plastics technology and evolving modular demands from the automakers will ensure that plastics play an ever-widening role in cars of the future.