Comprehensive investigation of reclaimed carbon fibre reinforced polyamide (rCF/PA) filaments and FDM printed composites

Reclaimed carbon fibre reinforced polyamide-6 (rCF/PA) filaments were prepared and deposited as test coupons with up to 40 wt% fibres under processing conditions derived using melt flow index and printing parameters. The effect of fibre content on the thermal properties, fibre length, fibre orientation, tensile properties, porosity and fracture morphologies was analysed. Overall, the 20 wt% and 30 wt% samples exhibited the best mechanical performance although the latter showed greater variability associated with fibre breakage. The tensile strength and modulus of the optimal 20 wt% coupons were improved by up to 175% (to 150 MPa) and 329% (to 7.8 GPa) respectively, compared with unreinforced PA and indicated a high degree of fibre alignment, relatively high degree of crystallinity, and low porosity (<6%). Notably, the mechanical performance of the 40 wt% composites dropped significantly as a result of fountain flow, poor fibre alignment and high porosity (>20%).