Investigation of a recyclable flax–acrylic composite structure (FLACS) for construction applications

Sandwich composite structures combine high stiffness, mechanical strength and low weight, making them attractive for panel applications in construction. However, their limited reprocessability, arising from the use of thermoset matrices that cannot be remelted after crosslinking, restricts their recyclability and sustainable use. This study reports the development of a recyclable sandwich composite structure based on flax fibers and a liquid polymethyl methacrylate (PMMA) thermoplastic matrix (FLACS). The work includes the fabrication of the core and face sheets, as well as the complete sandwich structure, using a combination of resin infusion and compression molding techniques. Mechanical testing revealed a bending strength of 41 MPa, a compressive load capacity of 19.6 kN and an energy absorption of 14.1 J under low-velocity impact. With a density of 234 kg/m 3 , the material demonstrates high specific mechanical performance. FLACS was subsequently subjected to a single mechanical recycling cycle followed by thermo-mechanical processing, without the addition of virgin polymer. The results demonstrate the feasibility of recovering the material as feedstock for manufacturing new composite panels suitable for scalable construction applications.