For years, BMW has been a trendsetter in automotive composites manufacturing. The lessons the OEM gained from the game-changing i3 now serve as the basis for the use of CFRP in serial production and future development of new BMW motorcycles and automobiles. Recently, BMW’s Motorrad division took another step forward, announcing that it has developed and manufactured a CFRP rear swinging arm for the HP4 Race motorcycle.
The swingarm project was by the German Federal Ministry of Education and Research as part of the leading-edge cluster MAI Carbon. The aim of the project was to develop a process that enabled the cost-effective volume-production use of CFRP in structural components subject to high levels of continuous stress. BMW says In the case of the swingarm, it was able to create a cost-efficient manufacturing process suitable for the large-scale production of injection molded components made CFRP with thermoplastic tape reinforcements.
BMW says the swingarm, which garnered an award at JEC last month, builds on the success of the industrial RTM technology used to make the motorcycle’s chassis.
“We opted for chassis components under continuous load since the requirements involved are especially demanding,” says project manager Elmar Jäger. He adds: “While car chassis parts are concealed, the visible motorcycle rear swinging arm was ideal for our project since the forces at work are immediately evident. Our production technique uses [CFRP] in the form of high-strength endless fibers where this is required by the stress pattern, while an injection mold part with short [CFRP] recycling fibers is used where the stress levels are not as high. In this way, we developed a cost-efficient design that can be scaled according to requirements by inserting endless fibers with varying levels of strength in the same tool. These were the points that impressed the international jury. The insights we gained from this motorcycle component are equally valuable from the point of view of car development and can be applied accordingly.”
According to BMW’s Joachim Starke, in addition to achieving weight benefits and cutting costs significantly, the company also managed to develop a technology that allows precise configuration of component properties by using a variety of composite and metal inserts. BMW says this scalability means that a single tool can be used to produce a wide range of different components at cycle times of less than a minute. The maximum strength can be adjusted by means of additional CFRP panels which can be thermoplastically joined.