Intelligent lightweight automotive construction solutions

Intelligent lightweight automotive design solutions based on polyamide hybrid technology from LANXESS helps cut vehicle fuel consumption and CO2 emissions.

Polyamide 6 and 66 (PA 6 and PA 66) grades in particular offer great potential for reducing weight in automotive construction. This fact is demonstrated by a number of concepts – some already used in series applications – developed by the Semi-Crystalline Products business unit of LANXESS, often in cooperation with partners. “The key feature of these innovations is that they don’t just reduce weight – at the very least they cost no more than established series solutions. Furthermore, we are also able to generate added value in most cases by integrating functions,” explains Ralf Zimnol, head of Application Development in the Semi-Crystalline Products business unit.

Hybrid technology – new applications, new material concepts Plastic/metal composite technology with polyamide – also known as hybrid technology – has been used in the production of lightweight and highly integrated automotive front ends for more than ten years. Car roof frames – and more recently, brake pedals – are also series-produced using this technology. “We have recently been able to develop a car brake pedal using our polyamide 6 Durethan* BKV 30 H2.0, which is around 40 percent lighter than a comparable product made purely of sheet steel,” recounts Zimnol.

New highly filled polyamides and polyesters such as Durethan DP BKV 60 EF H2.0 offer completely new automotive design potential for both hybrid and all-plastic parts. The 60 percent glass-fiber-reinforced PA 6 can be processed in the same way as a standard PA 6 with 30 percent glass fiber reinforcement and offers a similar level of flowability. Because of its high elasticity modulus, it exhibits around 100 percent higher stiffness, which means that component weight can be reduced considerably thanks to thinner walls, while offering the same mechanical performance. These components cost less, too. “A front end made using this high-tech thermoplastic would be around 35 percent lighter than a series-produced component made using a standard PA 6 with 30 percent glass fiber reinforcement,” explains Zimnol.

“Smart” material combinations also help reduce automotive weight in hybrid technology. For example, the aluminum hybrid front end in an Audi TT is 15 percent lighter than the equivalent made with sheet steel. Durethan BKV 30 H2.0 is the plastic used in this application. Another approach employed by LANXESS is based on composite sheets. These consist of a polyamide matrix embedded with a special fabric made of continuous fibers. The sheets are thermoformed and reinforced with polyamide using an injection molding procedure. The end result is all-plastic hybrid parts that are much lighter, stronger and stiffer than their steel counterparts. “The special feature of this application lies in combining the integration potential of injection molding with a strong adhesive bond to the composite sheet’s polyamide matrix. It also eliminates the need for corrosion protection for the sheet steel,” continues Zimnol.

Today, hybrid composite sheet systems, developed by LANXESS in cooperation with industrial partners, are used in the production of between 30,000 and 50,000 automotive components a year. “This technology is becoming increasingly popular for components in niche-market vehicles. Potential applications include “classic” hybrid components and ones that require a very stiff surface, such as spare wheel recesses and bulkheads.”

Lightweight bodywork structural inserts for improved safety Weight can be cut in the bodywork, too, if it is reinforced with polyamide. This is demonstrated by a new generation of injection-molded structural inserts using the glass-fiber-reinforced PA 6 Durethan BKV 35 H2.0 as the support. The inserts cut the weight of the bodywork of the new Citroen C4 Picasso by some 12 kilograms. In the event of a crash, nine inserts support the bodywork sheet steel, thus preventing the sheet steel structures from buckling prematurely or failing. This is one of the reasons why the C4 Picasso passed the Euro NCAP crash test with top marks.

The structural inserts are based on CBS (Composite Body Solutions) technology from L&L Products Europe. They are located in the lower section of the A pillar, in the lower and upper sections of the B pillar and in the crossmember above the rear axle. In addition to the polyamide support, they also consist of a high-density structural foam. As the cathodic dip coating
(CDC) dries, the structural foam expands, bonding the support with the bodywork being strengthened to create a solid macrostructure. Unlike polypropylene, Durethan BKV 35 H2.0 is able to withstand the CDC temperatures, which can reach up to 200 °C.

* Trademark of LANXESS AG.

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