Manufacturing of isogrid composite structures by 3D printing

In this research, isogrid panels in polyamide reinforced with short carbon fibers were manufactured by means of a 3D printing fused filament fabrication process. Before printing, the composite material was dried for 4 hours at 120°C in order to remove the humidity adsorbed by the polyamide. Then, during the printing process, the spool was kept at 70°C. The extrusion was performed at 240°C, with an infill density equal to 100%. The effect of geometric parameters, in terms of rib thickness and cell height, on the compressive strength and buckling behavior of the isogrid panels was investigated by means of compression tests carried out at room temperature on a servohydraulic testing machine. It was shown that the specific maximum compressive load at the onset of buckling increases with rib thickness. Furthermore, the isogrid panel characterized by the lowest cell height exhibits the highest specific maximum compressive load. Finally, the analysis of the isogrid panels after testing showed that failure is caused by global buckling failure mode; this suggests that the structure slenderness is higher than that of the ribs.