Effect of Post Heat Treatment on Mechanical Properties of 3D Printed PEKK / SCF Composites

Three dimensionally printed poly(ether‐ketone‐ketone) (PEKK)/short carbon fiber (SCF) composites are increasingly used for aerospace applications. Due to slow crystallization rate during the 3D‐printing process, 60/40 PEKK grade polymer requires post heat treatment (i.e., annealing) to enhance its crystallinity and mechanical properties. Therefore, the crystallinity of the as‐printed and annealed (2 h at 200°C) specimens was determined using density measurements, differential scanning calorimetry (DSC), and x‐ray diffraction (XRD) methods. The density method indicated an increase in crystallinity of neat PEKK from 0.73% (±0.81) (for as‐printed) to 18.24% (for annealed). DSC results demonstrated a marked increase in crystallinity from 0.96% (for as‐printed) to 27.01% (for annealed) for neat PEKK. The crystallinity of the composites further increased with SCF content. XRD demonstrated slightly higher crystallinity that is, 32.75%, 38.79%, and 44.03%, for the annealed neat PEKK, 10 and 20 wt% composites, respectively. This resulted in significant increase in tensile strength and elastic modulus of the composites compared to neat PEKK, highlighting the importance of post‐heat treatment on mechanical properties of the 3D‐printed PEKK/SCF composites.