Pushing the Fundamentals of Mechanical Composite Recycling

Modern industries increasingly rely on fiber-reinforced composite materials, such as glass- and carbon-fiber composites, because they are lightweight, strong, and durable. These materials are essential for applications like wind turbine blades, passenger transport vehicles, and aircrafts. However, once they reach the end of their service life, they pose a major environmental challenge. Unlike metals, fiber reinforced composites, especially those based on thermosetting polymers, are difficult to recycle, and many are still incinerated or landfilled. Mechanical recycling, which breaks composites down into reusable material fractions, is considered one of the most promising and scalable solutions, but its true potential is still not well understood from a micro- and mesoscopic scale. The FuMCoRe project addresses this gap by investigating how used composite materials can be reused and thus recycled at a fundamental level. The central idea is that the performance of recycled composites strongly depends on the microscopic interfaces between fibers and the surrounding polymer matrix. These interfaces control how loads are transferred within the material, yet they are poorly understood, especially after aging and recycling. Experimental testing, advanced modelling, and sustainability assessment are combined to build a comprehensive understanding of these interfaces. First, representative glass- and carbon-fiber composites are selected and carefully manufactured. Their mechanical behavior is then analyzed in both pristine and artificially aged states, simulating long-term exposure to environmental influences such as UV radiation and humidity. Special focus is placed on measuring how the bonding between fibers and matrix and neighboring lamina plies changes due to aging and recycling. Based on these measurements, the project develops multi-scale models that describe interface behavior from the molecular level up to structural components. Models developed and calibrated on coupon level are subsequently upscaled to (sub)component level to provide a proof of concept on the significands to macroscopic structures. In parallel, the project evaluates the environmental impacts of composite recycling using life cycle assessment methods, allowing mechanical recycling strategies to be assessed not only technically but also in terms of sustainability. FuMCoRe links material science, mechanical modelling, and life cycle assessment to determine when and how mechanical composite recycling is feasible. The results will enable better material selection, recycling-friendly product design, and informed decisions on future recycling technologies, while improving mechanical recycling processes and supporting a circular economy.