Effect of Printing Orientation on Microwave Absorption Properties of Additively Manufactured High‐Performance Polymer Composites

ABSTRACT The growing demand for stealth technologies has accelerated the development of efficient and easily manufacturable microwave‐absorbing materials. In this study, short carbon fiber (SCF) reinforced poly(ether‐ketone‐ketone) (PEKK) composites were fabricated using fused filament fabrication (FFF). Samples with varying thicknesses (1–4 mm) were printed in both horizontal (H) and vertical (V) orientations to evaluate their microwave absorption behavior. Thermal analysis revealed that incorporating SCF slightly increased the melting temperature and crystallinity of PEKK, with crystallinity rising from 27.1% to 32.51% for the 20 wt.% SCF composite. Improved thermal stability was also observed from thermogravimetric analysis. Dielectric properties increased gradually with increasing SCF loading. Importantly, both printing orientation and sample thickness influenced absorption performance. H‐printed composites demonstrated superior microwave absorption compared to V‐printed ones, with the PEKK/10 wt.% SCF sample achieving a maximum reflection loss (RL _max ) of −34.74 dB at 9.29 GHz for a thickness of 2.5 mm. Unlike conventional studies that focus solely on material composition, this work highlights the combined roles of processing parameters and thickness in tuning absorption behavior. The results demonstrate that 3D‐printed PEKK/SCF composites offer competitive performance, with the added advantages of lightweight, efficient, and customizable microwave absorbing materials.