The recycling of composite materials is a strategic issue for sustainable development, particularly in the sector of hydrogen tanks for transport. It is with this in mind that the CIRCULAR-2 project was launched in March 2024. Funded by the ANR-DFG, this Franco-German project aims to improve the circularity of wound structures made of thermoplastic matrix composites through an innovative design and an optimized peeling disassembly process.

A major challenge for the recycling of composites

Hydrogen tanks, essential to the energy transition, are currently manufactured from wound composites, often with a thermosetting matrix. However, to support a circular economy, the transition to recyclable thermoplastic matrices is underway. Nevertheless, their recycling, while preserving their mechanical properties, remains a challenge.

The objective of CIRCULAR-2 is to preserve the continuity of the fibers and maintain the coating in the matrix, in order to maximize their reuse. Recent studies have already demonstrated the potential of peeling disassembly, highlighting in particular the key role of interlaminar properties in material recovery.

Innovations of the CIRCULAR-2 project

To ensure the efficient reuse of recovered strips, CIRCULAR-2 explores two design strategies:

1. Functionalization of strip surfaces: This strategy aims to modify the interfaces under thermomechanical constraints to improve the peeling process.

2. Adaptation of process parameters and winding stratification: The objective is to limit the nesting of layers and prevent fiber breakages during peeling, thus improving the integrity of the material.

In addition, two disassembly techniques will be studied to optimize material recovery:

• Ultrasonic assistance: A method to weaken the layer interface.
• Low temperature or high peeling speed work: This approach aims to reduce mechanical alterations and preserve the material properties.

The recovered strips will then be rewound and subjected to mechanical characterization tests to assess their performance after manufacturing, peeling and reuse. A multi-scale multi-physics simulation tool will also be developed to model these processes, while an assessment of the environmental footprint will complete the study.

CANOE’s role in CIRCULAR-2

As a technical service provider, CANOE will actively contribute to the project at different levels:

• The manufacture of tubular parts by filament winding from impregnated strips, under various experimental conditions.
• The hosting of a doctoral student from the École des Mines d’Albi, Lucas Sieger, on its Pau site for a period of three years.
• The development of a peeling protocol on its dedicated bench, by providing the characterization means and its expertise in the analysis of composite materials.

A Franco-German collaboration for sustainable innovation

CIRCULAR-2 brings together leading players in composite materials research:

Coordinator: Mines d’Albi

Partners:

• INATECH (University of Freiburg)
• Fraunhofer EMI
• CANOE (service provider)

With CIRCULAR-2, CANOE is strengthening its commitment to composite recycling and innovation for a sustainable circular economy.

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