Infill strategies for 3D-printed CF-PEEK/HA-PEEK honeycomb core-shell composite structures

Core-shell composite structures with a carbon fibers reinforced polyetheretherketone (CF-PEEK) honeycomb core and a hydroxyapatite reinforced polyetheretherketone (HA-PEEK) solid shell were printed by a multi-material fused filament fabrication process. The effects of deposition paths on the mechanical properties of the speci-mens were investigated. Manufacturing defects were characterized by an optical microscope and a micro-X-ray imaging system, and the defect formation process was detected by a high-speed camera. In-plane and out-of-plane compression experiments were conducted to analyze the compression behaviors of the specimens. It was found that the specimens printed by crossing paths had inferior compression strength because of the for-mation of manufacturing defects at the joints of two deposition lines. By using non-crossing printing paths, the out-of-plane compression strengths of the square honeycomb core specimen and its composite structure coun-terpart were improved by 12.5 % and 8.3 %, respectively, whereas those of the triangular honeycomb core specimen and its composite structure counterpart were enhanced by 17.0 % and 18.4 %, respectively.