PulPro-SMC project concludes after three years of research. It works even without a weld seam, with a 20% weight reduction

The final meeting of the PulPro-SMC research project took place at the end of May. After three years of development work, the results were presented together with the partners: a material-bonded joint for fiber-reinforced composite structures created in a single pressing process.

The problem that was solved: Fiber composites are lightweight and strong, but joining them has always required a compromise. Adhesives hold, but not perfectly. Screws weaken the fibers. Until now, every joint was a potential weak point.

With PulPro-SMC, pultrusion profiles and SMC (Sheet Molding Compound) nodes fuse together under pressure and temperature to form a material-bonded connection. No separate joining technique, no weak points, and 20 percent lighter than conventional steel construction.

At the final meeting, all project partners presented their results in lectures, live pressing tests were conducted, and the demonstrator was unveiled: a real sidewall segment for rail vehicles.

The results at a glance: The material-bonded joint is formed in a single process step; the component is 20 percent lighter than in conventional construction; the mechanical properties are actually better than the FEM calculations; and the fire protection meets HL2 R1 standards.

Fire protection posed a particular challenge. Aluminum hydroxide, used as a flame retardant, significantly complicated processing during pultrusion and SMC pressing. The fact that it worked nonetheless is a testament to the team’s effort.

Each partner made its contribution: Fraunhofer IWU handled the development and testing of the pultrusion process, the Polynt Group Composites was responsible for the development of the SMC material, Conbility GmbH handled tow-preg production and process scaling, Modellbau Roth GmbH developed the flexible pultrusion tooling, and LSE was responsible for the press tooling and the processing chain.

Thanks also go to the associated partners AUDI AG, Huntsman Corporation, and ZOLTEK.

What’s next? Plans include integrating the process chains with a focus on automation and cost reduction, prototyping in vehicles, and transferring the technology to other applications with high lightweight construction requirements.

The project is funded within KoPa4Mobility by the Federal Ministry for Economic Affairs and Energy. Support is provided by TÜV Rheinland Research and Innovation Management.