Toward a new generation of recyclable composites

The PEPR RECYCOMP project, in collaboration with the FEMTO-ST Institute, is developing recyclable high-performance composites for a circular economy.

Composites, which combine a fibrous reinforcement (carbon, glass, flax, etc.) with a polymer matrix, offer both lightness and mechanical performance.  These materials are thus increasingly used in many industrial sectors such as aerospace, automotive, energy, and sports. However, recycling them by separating the fiber and matrix components—remains a complex challenge today, exacerbated by the ever-increasing volume of end-of-life materials.

As part of the PEPR (Priority Research Programs and Equipment) “Recycling, Recyclability, and Reuse of Materials,” the RECYCOMP project (ANR-22-PERE-0005) aims to address this major industrial and environmental challenge by developing a new generation of recyclable organic matrix composite materials without compromising mechanical performance.Bringing together nine research laboratories from across the country, this four-year project—which began in February 2023—explores two innovative approaches: supercritical solvolysis and twin-screw extrusion, using end-of-life components from wind turbine blades, ships, and automotive sandwich structures.  In addition, the project also proposes incorporating the recycling process into the material’s design from the outset. For example, flax fibers are first surface-treated with iron oxides to impart magnetic properties to them, enabling the selective recycling of their components.

The contribution of the FEMTO-ST Institute, through Adam LEVEZIEL’s thesis, is to characterize the interfacial properties of the materials developed in the RECYCOMP project at the micro-scale. Indeed, the fiber-matrix interface plays a crucial role in the mechanical performance of composites. To this end, a comprehensive study was conducted on the detachment of microdroplets from individual fibers. This test involves measuring, on a single fiber approximately 10 to 20 µm in diameter (thinner than a human hair), the force required to detach a microdroplet of polymer resin in order to evaluate the fiber-matrix bond in a composite.

In particular, an in situ device was developed with support from the MIMENTO, MIFHySTO, and AMETISTE platforms to enable this test to be conducted in an X-ray microtomograph and thus observe, for the first time in real time, the interfacial damage mechanisms responsible for the composite’s failure. The results obtained therefore provide a better understanding of the behavior of the fiber/matrix interface in the materials developed in the RECYCOMP project.

Ultimately, this research paves the way for the development of materials that are more durable, high-performance, and easier to recycle, addressing the environmental and industrial challenges of the future.