The main aim of this work was the investigation of the possibility of replacing the heavy metallic meshes applied onto the composite structure in airplanes for lightning strike protection with a thin film of Tuball single-wall carbon nanotubes in the form of ultra-light, conductive paper. The Tuball paper studied contained 75 wt.% or 90 wt.% of carbon nanotubes and was applied on the top of carbon fibre reinforced polymer before fabrication of flat panels. First, the electrical conductivity, impact resistance and thermo-mechanical properties of modified laminates were measured and compared with the reference values. Then, flat panels with selected Tuball paper, expanded copper foil and reference panels were fabricated for lightning strike tests. The effectiveness of lightning strike protection was evaluated by using the ultrasonic phased-array technique. It was found that the introduction of Tuball paper on the laminates surface improved both the surface and the volume electrical conductivity by 8800% and 300%, respectively. The impact resistance was tested in two directions, perpendicular and parallel to the carbon fibres, and the values increased by 9.8% and 44%, respectively. The dynamic thermo-mechanical analysis showed higher stiffness and a slight increase in glass transition temperature of the modified laminates. Ultrasonic investigation after lightning strike tests showed that the effectiveness of Tuball paper is comparable to expanded copper foil.

Unlike typical fiber-reinforced polymers, aerospace composites consist of 90% carbon and 10% glass fabrics impregnated with thermosetting resin. Due to the strong bonding between fibers and the thermoset nature of the matrix, recycling these materials is particularly challenging. This study evaluates mechanical recycling of aircraft composite waste via industrial grinding and chemical recycling through a solvolysis process. Recovered fibrous fractions were integrated into an epoxy matrix at 50 wt% loading using hot-pressing and into polyamide 12 at 15 wt% via a twin-screw extrusion process. The mechanical results showed that chemically recycled fibers in epoxy reached a flexural modulus of 9.9 GPa and strength of 112 MPa, significantly outperforming mechanically recycled fillers (6.1 GPa and 98.0 MPa) compared to virgin carbon fibers (11.3 GPa and 132 MPa). In PA12, the addition of chemically recycled fibers yielded a 2.14 GPa modulus and a 67.7 MPa strength. Furthermore, life cycle assessment confirmed that both recycling routes drastically reduce global warming potential and aquatic ecotoxicity compared to landfilling. These findings indicate that while mechanical recycling is simpler, chemical solvolysis provides a superior pathway for the high-value circular reuse of complex aerospace waste in new thermoplastic and thermoset applications.

This preliminary study evaluated printed conductive meshes as embedded sensors for damage detection in polymer sandwich composites. Meshes based on thermoplastic polyurethane and thermoplastic copolyamide were placed in three positions. Electrical measurements were combined with impact testing, ultrasonic inspection, active thermography, and optical microscopy. Sensor response depended on mesh material and position. The thermoplastic polyurethane mesh was effective only at the core-laminate interface, whereas the copolyamide-based mesh showed thermal changes in all positions. Surface-mounted meshes produced the smallest delamination areas. The results confirm the potential of conductive printed meshes for thermographic damage detection in sandwich composites.

PBT composites with multi-walled carbon nanotubes (MWCNTs) and graphite were obtained for use as sensors in conventional non-destructive testing. Their electrical conductivity, thermal diffusivity, electrothermal properties, and piezoresistive response were investigated. PBT/MWCNT composites showed the highest strain sensitivity, while PBT/MWCNT–graphite hybrid composites showed better electrical stability and better heat transfer, which indicates their potential as sensors in conventional non-destructive testing.