Study on recycling carbon fibre thermoplastic prepreg waste

In order to reduce the environmental burden by the weigh saving of vehicles, fibre reinforced plastics have been used as metal substitutes. The application of CFRTP (carbon fibre reinforced thermoplastics) is expected because of its high mechanical property together with process ability. However, there are unavoidable wastes when CFRTP prepreg sheets are cut into specific geometries to charge moulds with them. Therefore, it is necessary to utilize the CFRTP wastes by a recycling system from both the environmental and economical point of view. Recently, hybrid injection moulding that combines the press moulding and insert injection moulding has attracted attentions. The hybrid injection moulding system is as follow. After heated insert material is pre-formed by pressmoulding, the pre-formed insert material is overmoulded by injection moulding machine. These processes are carried out in the one cycle. In this paper, we propose the recycling method of prepreg wastes and characterize the recycled material. Furthermore, we investigated the potency of the recycled material for the hybrid injection moulding. We carried out numerical analysis to examine the interfacial characteristics. Our recycled material is prepared as pellets by neading, the wastes of prepreg in twin-screw extruder with neat polymer. The fuzzless pellets with good fibre dispersion were obtained in low volume fraction of carbon fibres. In spite of the absence of longer fibres, they showed excellent mechanical performance in comparison with conventional materials designing the preferable process conditions. This mechanical advantage would be due to the fact that the recycled pellets were made from the prepreg sheet which had good interfacial adhesion strength. In contrast, the localization of fibres was observed in high volume fraction of fibres and the mechanical property did not improved. This recycled material has a beneficial effort on the hybrid injection moulding. They also achieved excellent interfacial adhesiveness for the hybrid injection moulding between the injected material and the inserted material. It was found that the cost effective recycle pellets which had excellent mechanical performance could be produced optimizing both the fibre volume fraction and process condition in this recycling system.