A novel approach to rapidly process vitrimer composites using power ultrasonics

Abstract Fibre-reinforced polymers (FRPs) play a key role in lightweight structural design but are often processed using high pressure, temperature, and time, particularly when thermoset matrices are used. Vitrimers, which feature dynamic covalent networks, offer a transformative alternative by enabling reshaping, repair, and recycling after curing, making them highly attractive for sustainable composite manufacturing. However, vitrimer composites are highly desired, but are challenging to be processed. This feasibility study presents a novel ultrasonic moulding process that was combined with ultrasonic joining and that enables the rapid fabrication of three-dimensional carbon fibre-reinforced vitrimer (CF-Vitrimer) structures. Using a 20 kHz ultrasonic system, CF-Vitrimer prepreg plies were moulded and joined in 5 seconds per operation. The process requires only 2500 N of force (equivalent to a pressure of 1.5 MPa), up to 30 times lower than conventional thermoforming, and is about six times faster than advanced infrared-heating assisted techniques. Consolidation and bonding were achieved through superimposed ultrasonic oscillations and moderate forces, eliminating the need for prolonged heating cycles. Mechanical tests confirmed that durable samples were fabricated only when moulding forces exceeded 1500 N. Shear test results showed a distinct increase in strength and stiffness with increasing forming pressure, validating the critical energy threshold for vitrimer activation. Microstructural analysis revealed high layer integrity and undamaged fibres, confirming effective consolidation and joint integrity without matrix degradation.