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The drive for weight savings in the auto industry has spawned a growing range of applications for overmolding of so-called “organic sheet composites.” These are continuous-fiber fabrics preimpregnated with thermoplastic resin (usually nylon), which are then heated until soft and placed in an injection mold, where they are formed and overmolded in selected areas with additional nylon to add ribs, attachment points, etc. The latest roll-out of new applications includes three nylon-on-nylon overmolded composites:
•The new Opel Astra OPC sport coupe, introduced at the Geneva Auto Show last month, has a seat pan (pictured) made from a specialty Ultramid nylon frm BASF AG (U.S. office in Wyandotte, Mich.). This is the first auto seat pan using this technology on a production vehicle. The glass-fabric composite is overmolded with short-glass reinforced nylon. (At the K 2010 show, BASF showed off a seat back made in a similar manner using a special Ultramid nylon 6 for Faurecia. It’s expected to hit the road in a couple of years. See Dec. '10 Close Up.)
•Another first for this “composite sheet hybrid” technology is a car brake pedal of nylon 6 from ZF Friedrichshafen AG in Germany. A composite sheet of nylon 6 with 47% by volume continuous glass fibers is heated, thermoformed, and cut to size before overmolding with Durethan BKV 30 H2.0 nylon 6 with 30% short glass from Lanxess AG (U.S. office in Pittsburgh). The preimpregnated sheet is a Tepex dynalite grade from Bond-Laminates GmbH in Germany. It weighs 355 g, half as much as a steel brake pedal.
•Another new part is still an advanced engineering project in Germany, involving Lanxess, Bond-Laminates, KraussMaffei Technologies GmbH, Takata-Petri AG, and Chrisian Karl Siebenwurst GmbH. The passenger airbag housing is made of Tepex dynalite 102 RG 600 nylon 6 sheet with 47% continuous glass, overmolded with Durethan DP BKV 240 H2.0 from Lanxess containing 40% short glass. The airbag housing weighs more than 30% less than a current commercial version injection molded of nylon 6. Due to the high strength and stiffness of the sheet composite, the side walls were thinned from 3-4 mm down to 0.5-1 mm, resulting in considerable cost savings.
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