Low Melt Viscosity High‐Performance Polyether Ether Ketone—Carbon Fibers Composites for Additive Manufacturing: An Insight on Microstructure, Crystallinity, and Correlation With Thermo‐Mechanical Properties

ABSTRACT In this paper, polyether ether ketone (PEEK) composites reinforced with CFs (20%; 30%, 40% by weight) have been manufactured and fully investigated by means of structural, morphological, and functional analytical techniques. The structural analyses by X‐ray Diffraction (XRD), Wide Angle X‐ray Scattering (WAXS) and Small Angle X‐ray Scattering (SAXS) revealed nonlinear crystalline disorder in the PEEK matrix induced by the incorporation of different amounts of CF. Raman spectroscopy corroborated these findings, showing shifts in key vibrational bands associated with filler‐polymer interactions and crystalline disorder. Thermal analysis indicated that the obtained composites maintain high thermal stability (degradation temperature > 540°C) with slight changes in melting behavior and crystallinity degree (36 ➔ 30%) due to CF inclusion. Furthermore, the presence of CF filler increases the mechanical properties of the composites (E > 19 GPa, σ _max > 170 MPa). According to these specific rheological properties, the CF‐modified PEEK composites are suitable for extrusion‐based applications, such as 3D printing.