Carbon fibre damage during 3D printing of polymer matrix laminates using the FDM process

Fused deposition modelling (FDM) is an additive manufacturing process used for the 3D printing of continuous fibre-polymer laminates. However, the mechanical properties of laminates printed using the FDM process are often relatively low. The damage caused to continuous carbon fibres during different stages of the FDM process from the initial feedstock material to the final 3D printed material is investigated to determine the causes of the properties decay. The effect of the process stages on the damage and mechanical properties of a continuous carbon fibre/polyamide filament material is determined. Fibre damage occurs at multiple stages of the FDM process, although most damage occurs in the final stages when the FDM filament is extruded through the printer nozzle and then printed. The average strength of carbon fibres within the FDM filament evaluated in this study is reduced ~33% by the FDM process. The tensile strength and compression kinking stress of the 3D printed filament material are reduced by ~60% and ~25%, respectively. The causes of the damage and the resultant reductions to the mechanical properties of the FDM filament during 3D printing are identified.