First efforts on recovery of thermoplastic composites at low temperatures by power ultrasonics

Fiber reinforced composites possess exceptional mass-specific properties and therefore offer a high potential for weight reduction in lightweight applications. However, the need to recover, remanufacture and recirculate polymer composites at lower temperatures is still an area to be addressed. For a cleaner and more sustainable reuse of polymer composites at their end-of-use (EoU) phase, a materials circularity strategy can be applied. This work describes a novel method and proof-of-concept to recover carbon-fiber (CF)/ polyether-ether-ketone (PEEK) composites. It is composed of three steps: i.) initiation of controlled interlaminar pre-cracks by power ultrasonics, ii.) propagation of the pre-cracks under peel-like loading, and iii.) ultrasonic reconsolidation of the separated layers. Microscopic and mechanical investigations on the composite materials before and after the separation and reconsolidation, shows near-identical fiber-bundle arrangements, with the reconsolidated composites retaining approximately 89 % of its mechanical properties compared to the original laminate.