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Lightweight vehicle design: how low can you go?

That is the question automakers everywhere are wrestling with, as was amply demonstrated at last week's VDI Engineering Plastics Conference. Aesthetics, safety, economics, and material availability were just a few of the concerns that were raised in connection with lightweighting, during the discussion on the best strategies to employ. Just how light can vehicles become, and how to achieve this, without compromising on quality?

That is the question automakers everywhere are wrestling with, as was amply demonstrated at last week's VDI Engineering Plastics Conference. Aesthetics, safety, economics, and material availability were just a few of the concerns that were raised in connection with lightweighting, during the discussion on the best strategies to employ. Just how light can vehicles become, and how to achieve this, without compromising on quality? One strategy is the use of innovative materials and material solutions, such as those developed by specialized material manufacturers specifically for the automotive industry. Some examples are discussed below.

At the Lanxess stand, for example, the advantages of the Tepex line of continuous fiber-reinforced thermoplastic performance composites developed by its subsidiary company Bond-Laminates were being extolled with the display of a prototype infotainment bracket containing two back-injected Tepex inlays, designed for mounting an amplifier and a TV control unit in an Audi A6.

Formerly made from steel with two screwed-on amplifiers, the new design offers simpler mounting, using clips, in addition to cost and weight advantages through the use of Tepex organic sheet. Lanxess' new Durethan BKV 55 TPX with 55% short glass reinforcement, which has been optimized for processing with Tepex, was used as the matrix material. The improved flowability of this grade ensures good bonding between the ribbing and the Tepex, and thus good mechanical properties of the component. This hybrid technology is particularly suitable for thin-walled lightweight composite parts with large flow length/wall-thickness ratios.

Jaguar dashboard
Jaguar F-Type dashboard. Image courtesy Borealis.
Lanxess has also started cooperating with EconCore, a Belgian company specialized in the production of lightweight honeycomb-structured sandwich cores, to produce stiff and strong polyamide honeycomb cores that offer possibilities for loadbearing structural automotive parts, especially in sandwich structures, for example in combination with Tepex facings.

Borealis was showcasing the Fibremod instrument panel (IP) carrier for the Jaguar F-Type, which was developed in collaboration with Jaguar and Tier One supplier Dräxlmaier. Fibremod is a family of engineered short and long glass-fiber compounds that was officially launched last September.

As the name implies, the material can be transformed or a specific grade can be modified to fit specific customer needs and requirements. For the Jaguar F-Type, Dräxlmaier sought a material solution that would deliver very high stiffness and excellent impact performance, without compromising other key requirements such as dimensional stability. Moreover, the materials selected were required to contribute to overall vehicle weight reduction and competitive system costs.

A dilution system was developed based on 50% Fibremod GB601HP and 50% BE677AI, yielding a PP-LGF 30% with a well-defined performance profile for the IP carrier. This delivered the highest processing and end-use performance, while contributing to lower weight and overall system costs. Jost Eric Laumeyer, Borealis Global Marketing Manager Engineering Applications, commented that Fibremod solutions help partners and customers along the entire automotive value chain in their efforts to make vehicles lighter and reduce processing temperatures and energy requirements, all while reducing system costs. "Our customized glass-fiber reinforced PP solutions are at the cutting edge of innovation, bringing lightweight, extra strength, and impact performance to a wide range of automotive and appliance applications," he said.

At the stand of Styron Automotive, the focus was on the company's Pulse GX50 material, a polycarbonate/acrylonitrile butadiene blend that offers a 4% decrease in density compared to industry-standard PC/ABS grades and low carbon emissions (VOC) in the range of 10 ppm. According to Styron, it also provides outstanding resistance to heat distortion at temperatures up to 110°C, and high impact strength at temperatures as low as -30°C. The material is suitable for unpainted applications.

Because of its 4% lower density and the proprietary UV stabilizing technology allowing for unpainted applications, the material has been chosen by BMW and Mercedes for interior applications. The console, glove box, and trunk trim in the BMW i3 and the pillars and door panels in the Mercedes Benz C class are all made of Pulse GX50.

Building on the success of these interior applications, Styron plans to release a similar Pulse series focusing on exterior applications later this year.

Although not quite new, PolyOne was exhibiting an automotive aftermarket LED light that provided a good example of a lightweight metal replacement solution. By replacing aluminum with the company's Therma-Tech thermally conductive polymer in the heat sink, manufacturers can significantly reduce total part weight and optimize production and logistics.

At the stand of Swiss moldmaker Georg Kaufmann, who, together with partners developed what is known as LIPA (Lightweight Integrated Process Application) technology for the mass production of lightweight composite parts, a demonstration part produced via this process was on display. The process itself involves cut-to-size pieces of Tepex organic sheet, which are preheated, placed in the mold by a robot, and subsequently overmolded with a thermoplastic material to create the final part. The technology enables the production of endless-fiber-reinforced components using a series product manufacturing process.

An interesting, as yet untested development from Georg Kaufmann was on display that, according to Roger Kaufmann, could best be described as a thermoformed hose. The technology consists of weaving carbon or glass fibers together into a hose, which is then transferred to a mold, together with a thermoplastic such as PP. The mold is subsequently heated to 240°C for three minutes, after which air is pumped into the mold, raising the air pressure in the mold. This causes the fibers to be pressed against the hot wall of the mold. The materials come together, after which the part is finished under normal pressure (5-6 bar) used for thermoforming. The finished part, said Kaufmann, could replace different metal brackets under the hood. "It's strong enough,' he said. "But very much lighter. We're still testing it."

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