Tailoring anisotropy and mechanical performance of additively manufactured PEKK through annealing and architected design

Processing and post-processing parameters critically determine the structural performance of additively manufactured parts. Poly-ether-ketone-ketone (PEKK), a high-performance thermoplastic, offers considerable promise for aerospace applications. However, its mechanical behavior in material extrusion (MEX) remains constrained by pronounced anisotropy and weak interlayer bonding. Addressing these limitations requires understanding how printing architecture and post-processing jointly influence mechanical response. Therefore, the objective of this study is to evaluate the effectiveness of an optimized annealing protocol, established in our previous work (210 °C for 30 min), in reducing anisotropic behavior and enhancing mechanical performance across different raster orientations and architected structures. Tensile and flexural coupons were fabricated at raster angles of 0°, ±45°, and 90° using three infill patterns (line, concentric, and mixed) and tested before and after annealing. Additionally, compressive coupons of Schwarz G and Schwarz P lattices with 40 % relative density were examined to represent structural architected geometries, tested both parallel and perpendicular to the print-layer direction. Results show that reinforcement by annealing is pattern-dependent. At the maximum reinforcement, concentric infill yielded the greatest tensile strength improvement (29.5 %), whereas the 90° raster exhibited the largest flexural strength gain (17.6 %). For structural lattices, compressive strength increased by 37.5 % in Schwarz G, while a reduction of 18.6 % was observed in Schwarz P. While annealing enhanced stiffness, strength, and thermal stability, it also introduced dimensional changes and occasional void-related defects. Overall, this study demonstrates the interplay between anisotropic printing architecture and post-processing, providing pathways to tailor PEKK components for aerospace and structural applications requiring either superior strength (annealed) or enhanced toughness (as-printed).