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A new process from the composites sector will be used during production of the tailgate for the new Smart model.  This involves the first industrial use of E-LFT Technology, in which structural components can be mass-produced in one operating cycle.  The innovation will be presented at COMPOSITES EUROPE (23 to 25 September 2008, Essen) by Dieffenbacher GmbH + Co. KG from Eppingen (Baden-Württemberg).  The company participated in the development in a consortium project with Esoro AG, Weber Fibertech together with Smart GmbH as well as Acts GmbH & Co. KG.

The production facilities for compounding long fibre reinforced plastics and for manufacturing suitable components come from Dieffenbacher.  The company specializes in the production of LFT-D plant and Direct-SMC plant.  “The lightweight component systems unit for the automobile industry is a growth area for our company. For almost 40 years we have been supplying the plant for this industry,” states Heinrich Ernst, Manager of the Plastics Technology Product Division at Dieffenbacher.  “LFT-D has recently achieved annual growth rates of up to 15 per cent, with a rising tendency.”  He predicts that “with the SMC Direct process considerable increases are to be expected.”

E-LFT stands for endless fibre-reinforced long-fibre thermoplastic and is a further development of the long-fibre thermoplastic direct process, which eliminates the costly production of semifinished products.  The basis is a structure of long-fibre thermoplastic, which gives considerable scope for design for designers and engineers.  The reinforcing fibres are drawn into the already molten plastic matrix as continuous rovings. The component thus gains strength – also where crash safety is concerned.  In addition, the function elements can be directly integrated in the process, which eliminates assembly and inspection stages.

“At COMPOSITES EUROPE we present a uniform structure concept for the two Smart Coupe and Cabriolet vehicle variants”, says Ernst.  “Both the ABS-PC and also the aluminium tubular frame as well as the plastic concept of the previous Coupe variant are being replaced.”  The advantages of the component are multifarious.  Despite higher crash requirements there is no increase in weight; passenger protection from the side pillars placed in the tailgate in the event of a front impact at 40 mph is ensured.  In addition, there is increased structure rigidity in excess of 20 per cent.

According to the expert, “the component has an integrated, multifunctional storage compartment and, at the same time, serves as a seal for the rear door to the body and to the convertible top.  It is designed both for the dynamic as well as for the static load, it has an embossed, coloured surface and can be simply recycled.”  Other components that are manufactured in LFT-D with plant from Dieffenbacher are underbody covers and cW panelling for the VW Group and DaimlerChrysler, front end assembly carriers as well as dashboard carriers for the Smart.

According to the expert, “the direct process provides considerable potential for cost savings.  By circumventing the production of semifinished goods, the savings in material alone are 35 to 50 per cent.  Added to this are very brief cycle times of 20 to 25 seconds and double-tool operation.”  Ernst foresees considerable development opportunities for the use of composites in the automobile industry, especially for saving fuel, for the aerodynamics, for design aspects and through high possibilities for function integration.

This estimate is supported by the latest figures from the experts at the Federation of Reinforced Plastics e.V. (AVK).  In their latest market survey they detect an exceptional growth rate where glass-fibre reinforced thermoplastics are concerned.  In the meantime, LFT has gained a firm place in the automobile industry and is developing almost exclusively in this sector.  Particular mention is made regarding the further development of underside panels.  In the meantime, intelligent solutions have been found with which to protect the LFT underbody from the hot sections of the exhaust system.  It is said that sandwich elements will give this market new impetus.

Photo: Smart tailgate.jpg: This structural component of the new Smart will be manufactured by the E-LFT process (Photo: Dieffenbacher)