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Drive shafts getting lightweight builds

Researchers at the Fraunhofer Institute for Applied Polymer Research IAP (Germany), along with their partners, are developing a new, very lightweight drive and side shaft system for cars and trucks. The shafts' matrix consists of thermoplastic materials that can be recycled and have additional lightweighting and processing advantages.

Drive shafts made of fiber-reinforced plastics can reduce the fuel consumption of vehicles through their low weight, thereby helping to lower their environmental impact too. In cars and trucks, these shafts transfer the power from the gearbox to the wheels and have to withstand high loads in the process. For this reason, they are usually manufactured as multi-piece drive shafts and made of heavy materials such as steel, aluminum, or titanium alloy.

At Fraunhofer IAP, automated fiber placement technology (AFP) is used to produce new, very lightweight drive shafts made of carbon-fiber-reinforced plastics. Thanks to their thermoplastic matrix, the components can be recycled. [Credit: © WFBB, photographer: Jungblut & Büssemeier]

 

 

 

 

Current alternative-material drive shafts are made of carbon-fiber-reinforced plastic with a thermosetting matrix. As a result of their lower density and fewer required bearing positions, they are around 60% lighter than their metal counterparts and often feature better mechanical properties. However, they can still be further optimized in terms of weight and ease of recycling.

Researchers from Fraunhofer's "Center for Sustainable Lightweight Technologies" (ZenaLeb), a project group of the research division Polymeric Materials and Composites PYCO at Fraunhofer IAP, together with partners from industry, are dedicated to this task. The German Federal Ministry for Economic Affairs and Climate Action (BMWK) is funding the project.

"In the first step, we want to optimize wound drive and side shafts with a thermosetting matrix," said Felix Kuke, head of ZenaLeb. In the second step, we will develop shafts with a thermoplastic matrix."

Drive shafts with a thermosetting matrix are currently produced using filament winding. In this manufacturing process, filaments impregnated with resin are wound around a rotating axis under tension and cured in an additional step.

The new thermoplastic drive and side shafts, however, will be manufactured using automated fiber placement technology (AFP). "With AFP technology, prepregs, i.e., pre-impregnated tapes that contain carbon fibers, are heated by a laser and then placed on a rotating axis fully automatically and controlled by a robot," said Kuke. "Additional curing is not necessary."

Another advantage of AFP technology is the tapes can be cut during the process and placed at different positions to create new angles, winding patterns, and shapes. In other words, the drive shafts can be wound freely and are not limited by predefined winding patterns, as opposed to filament winding. This results in a lower weight compared to current thermosetting design methods.

According to calculations by Fraunhofer IAP, new designs using AFP can lower fuel consumption by 0.3% during the use phase and considerably reduce CO2 emissions for newly registered cars and trucks in Germany. In comparison to steel-based drive shafts, it is possible to achieve weight savings of more than 65%.

"The AFP process allows manufacturers to achieve high productivity rates," said Kuke. "Our goal is to implement the manufacturing concept for large-scale production."

Tracking the complete process chain to reduce the carbon footprint requires the product life cycle -- from the production of the base material to recycling -- to be mapped and monitored using integrated sensor systems. For this purpose, fiber-optic sensors and strain gages are wound into the drive shafts, and the manufacturing plants are equipped correspondingly.

The prepregs already feature a QR code that provides information on the fibers as well as the matrix system used, which is essential for recycling. By integrating product branding concepts and sensor systems, it is possible to assess the environmental impact of the production of the new shafts and to determine the required energy and resource consumption.

Digitization and simulation tools in the form of a digital twin support the optimization process as well as quality assurance and help to make the design more lightweight. "Suitable digitization tools allow us to calculate entire assemblies," said Kuke.

If you are interested in this technology, contacts at Fraunhofer can be found here: www.iap.fraunhofer.de/en/research/PYCO/construction-and-manufacturing-technologies.html.

Source: Fraunhofer Institute

Published June 2023

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