Economic production of composite parts
by Hans Diederichs
Composite materials such as carbon fibre reinforced plastics are still used sparingly in lightweight automotive engineering and have not yet made the leap into series production. The manufacturing costs for parts made of carbon fibre reinforced plastic (CFRP) are simply still too high. Within the research project "iComposite 4.0", Schuler and its partners have succeeded in reducing the costs for a prototype part by more than 50 percent and throughput times by more than 40 percent.
The reference component is a floor plate mounted under the engine and passenger compartment of an English sports car. Its structure must be designed for frontal impact, high torsional stiffness and seat load. While the costs for conventional production amount to almost 400 euros per part, they dropped to around 150 euros for iComposite 4.0. Throughput times went down from 73 to 46 minutes.
In the first production step, for which the RWTH Aachen Institute of Plastics Processing is responsible, a robot sprays the basic structure of short glass fibres. Next, an algorithm – developed by the Aachen Centre for Integrative Lightweight Construction (AZL) and CFRP supplier Teijin Carbon – calculates the individual tensile strength. Depending on this, another robot then lays the carbon fibre towpregs in a very specific process, which originates from Siemens and Broetje Automation Composites, thereby compensating for component variations. The optical control is performed by a 3D measuring system from Apodius.
Resin is then injected into the composite fibre mat that results from above-mentioned process. The resin hardens under the high pressure of the hydraulic Schuler press, which forms the part at the end. Die technology from Frimo specialists is also influencing this process. For the desired wall thickness, the press can directly impact the deflection of the die. This makes it possible to produce good parts right from the start, the rejection rate is reduced to zero.
So far, manufacturers of fibre composite parts use carbon mats as raw material that needs to be cut. The exploitation may decrease to up to 50 percent; that means that manufacturers cannot use almost half of the expensive carbon fibres. With iComposite 4.0 the required material is completely used, and the waste is zero. At the same time, the throughput time decreases while the output increases.
The integrated RFID chip from ID-Systec ensures the traceability ("track & trace") of the production data. All components of the production line that runs at the RWTH Aachen AZL are cross-linked to each other. The findings of the research project are now to be incorporated into industrial practice.
Source and photo: Schuler AG