In-situ consolidation of additively manufactured continuous fiber reinforced material: Technical approach and results

Additive manufacturing (AM) of continuous fiber reinforced composites (CFC) is becoming increasingly important in the field of lightweight construction. The major advantage lies particular in the automated manufacturing process and in the production of complex geometries. Most work was done with traditional fusion filament fabrication (FFF) and the lack of separate consolidation units. AM CFCs produced in this manner have shown 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. Recently, there were several efforts in modifying the FFF 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 FFF-CFCs. The present paper analyses the stated problem and proposes ways to decrease deconsolidation in FFF CF-PA6 laminates. For this purpose, we used a self-developed FFF 3D Printer 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 FFF laminates printed in a common 3D printer was performed. The controlled 3D printing consolidation process leads to a homogeneous distribution of fibers in the matrix material and to an improvement of the material parameters of the reinforcing composite.