Additive manufacturing of continuous carbon fiber reinforced polyamide 6: The effect of process parameters on the microstructure and mechanical properties

Additive manufacturing (AM) is becoming increasingly important in the field of component design. Continuous fiber reinforced composites (CFC) have been recently investigated to manufacture AM components. Recent works on AM CFCs printed by traditional continuous filament fabrication (CFF) have revealed increased consolidation-related volumetric flaws -i.e. deconsolidation defects decreasing mechanical performance. The presence of deconsolidation defects, normally indicates either poor process parameters selection or inadequate in situ consolidation. The latter is an intrinsic characteristic of traditional CFF, where there is no application of additional in situ consolidation pressure. Recently, there were several efforts in modifying the CFF of CFCs to minimize deconsolidation defects through in situ thermo-mechanical pressing. However, there are only limited fundamental knowledge on the in situ thermo-mechanical consolidation of CFF-CFCs. There are no consolidation models able to predict the consolidation level in the AM CFC. This work analyses the stated problem and proposes ways to decrease deconsolidation in CFF CF-PA6 laminates. For this purpose we used a self-developed CFF printing head coupled with a thermo-mechanical pressing unit. The influence of extrusion-, consolidation temperature, printing speed and in situ consolidation pressure on laminate microstructure and flexural strength was investigated. A comparison with CFF laminates printed in a common 3D printer was performed. Finally we introduce new simulation concepts for the in situ consolidation of AM CFCs.