Superior strength in the 3D-printed polyether-ether-ketone composites reinforced by annealing and carbon fibers

The light-weight, high-strength polyether-ether-ketone (PEEK) shows great potential for weight-sensitive, load-bearing applications. The adoption of PEEK in those applications has been accelerated by the recently emerged three-dimensional printing (3D-printing) technique. However, achieving high strength in the 3D-printed PEEK is still challenging. In this study, the mechanical strength of the 3D-printed PEEK is jointly reinforced with high-loading carbon fibers (CFs) and annealing treatment. The PEEK-CF composite filaments containing three different CF contents, ranging between 5 and 15 wt%, are first prepared in-house and subsequently printed into specimens. Both the tensile and flexural tests show that the composite containing 10 wt% CF exhibits the highest strength, reaching 114.7 and 139.2 MPa, respectively, the tensile strength of which amounts to a 35% increase from the unfilled counter-part. The annealing treatment on the printed samples further increases the strength of the composite both at room temperature and high-temperature. After annealing, the tensile strength of the 3D-printed PEEK-CF composite reaches 131.5 MPa at room temperature and over 60 MPa at 200 degrees C. The results from this study can spur new insights into design advanced polymer compos-ites with outstanding mechanical properties. Highlights center dot Custom-made PEEK-CF composite filaments with high CF content, up to 15 wt%center dot 3D-printed PEEK-CF composites exhibit very high tensile strength, reaching 115 MPa.center dot The annealing treatment further strengthens the printed composite, up to 131 MPa.center dot The jointly strengthened PEEK-CF composite remains strong at elevated temperatures.