Effects of Low-pressure Annealing on the Performance of 3D Printed CF/PEEK Composites

The interlayer bonding properties are normally unsatisfying for 3D printed composites owing to the layer-by-layer formation process. In this study, low-pressure annealing was performed on 3D printed carbon fiber reinforced polyether ether ketone (CF/PEEK) to improve the interlayer bonding strength. The effects of annealing parameters on the mechanical properties and microstructure were studied. The results showed that the interlaminar shear strength (ILSS) of CF/PEEK improved by up to 55.4% after annealing. SEM and μ-CT were also applied to reveal the reinforcing mechanism. This improvement could mainly be attributed to the increased crystallinity of the CF/PEEK after annealing. Additionally, annealing reduced the porosity of the printed CF/PEEK and improved the fiber–resin interface. This resulted in a reduction in the stress concentration areas during loading, thereby enhancing the interlayer bonding strength of CF/PEEK.