Back in 1967, a concept car was presented by BMW and Bayer at the plastics trade fair in Düsseldorf. The car, equipped with a 120 hp engine from BMW 1600ti, came to a kerb weight of only 850kg due to the broad use of plastics. This combination enabled the K67 to reach a top speed of 190 km/h: 15 km/h more than the BMW 1600ti.
The vehicle was certified for road use in the same year. However, of the five examples built, only two were able to drive on the road, as three were sacrificed in crash tests.
The idea behind the cooperation between BMW and Bayer was not just to develop a vehicle with a plastic body, as such already existed at the time. The goal was to develop a car ready for series production in which other assemblies were also made of plastic.
This goal has been achieved: the K67 has a sandwich floor assembly made of glass-fibre reinforced plastic (GFRP) and a foam core. The fuel tank was made of polyamide and the instrument panel and centre console of polyurethane.
From the structural-mechanical point of view, the use of a GFRP sandwich structure is particularly interesting. Sandwich structures are characterised by good specific mechanical properties, which are achieved by the clear separation of tasks between the face sheets and the core. The stiff and strong face sheets absorb the normal stress from the bending. The core structure located between the two face sheets is mainly responsible for increasing the distance between face sheets (and the second moment of area). In addition, the core absorbs the shear stresses that occur.
The Lightweighting Effect
The plastic car from Bayer and BMW reached a weight of 850 kg and met the requirements to be certified for road use. Among others, by reducing the kerb weight, the K67 was able to achieve a speed that was approx. 8.5 % higher than that of the BMW 1600ti, even though both vehicles had the same engine.
At the plastics trade fair in 2016 another concept car (K2016) with broad use of plastics was presented by Covestro AG.
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