Effect of fiber content on mechanical properties of carbon fiber-reinforced polyether-ether-ketone composites prepared using screw extrusion-based online mixing 3D printing

Abstract

The mechanical properties of carbon fiber-reinforced polyether-ether-ketone (CF/PEEK) composites are closely related to the fiber content. However, the low fiber content (typically below 20 wt%) that can be prepared by current material extrusion limits the application of the composites. In this work, CF/PEEK composites with up to 50 wt% carbon fiber content were manufactured using a custom-made screw extrusion-based online mixing 3D printhead. The impact of fiber loading on the rheological and flow characteristics of the composites was thoroughly examined initially. Subsequently, the influence of fiber content on the crystallinity and mechanical behavior of 3D-printed parts before and after annealing was further explored. The results indicated that adding CF and annealing significantly enhanced the strength and modulus of the 3D-printed composites within a fiber content range of 10 wt% to 40 wt%, compared to those of pure PEEK. At 40 wt% CF, the tensile and flexural strengths of the samples reached their maximum values at 135.9 MPa and 251.2 MPa, respectively, which were enhanced by 94% and 111% compared to those of the unannealed pure PEEK specimens. Also, these properties are the highest values achieved in 3D-printed short CF/PEEK composites. The mechanical properties of composites are affected by various factors such as fiber content, crystallinity, and internal pore defects when the fiber content is less than 20 wt%. However, when the fiber content exceeds 20 wt%, the influence of crystallinity on the mechanical properties becomes less significant. This study further explores the potential application of CF/PEEK composites and provides a novel approach for composite preparation.