Mechanical Behavior and Void Analysis of 3D Printed PEEK by Fused Deposition Modeling (FDM) with Varying Infill Patterns

Polyether ether ketone (PEEK) was printed via FDM using gyroid, line, and tri-hexagon infill patterns. Its effect on the mechanical behavior (tensile, flexural and compression) and the investigation of void percentage and orientation angles within the internal structure were studied. The line pattern showed the highest tensile strength at 55.46 MPa due to its internal structure with a higher number of deposited layers oriented along the direction of the stress enabling higher stress absorption, the laminate theory. The angular lines on both tri-hexagon and gyroid patterns provided disadvantage as supported by Timoshenko's theory where the internal structures acted like a beam which is prone to easier deformation. Line pattern also demonstrated the highest flexural strength at 103.67 MPa. The continuity of the pattern along the internal structure perpendicular to the direction of the force provided more effective transfer of stress. However, the highest compressive load was observed in gyroid pattern with 8,266.89 N. The redundancies in the internal structure design of gyroid pattern enabled more compression load absorption. Symmetry and internal angles in gyroid and tri-hexagon patterns allowed more compressive force which are more susceptible to fractures due to higher strains created. Lastly, void percentage showed line pattern with the lowest at 1.53%. In addition, the mean void orientation angle showed that the closer it is to 0o, the weaker the part.