Using a high shear melt-processing method, graphene-reinforced polymer matrix composites (G-PMCs) were produced with good distribution and particle-matrix interaction of bi/trilayer graphene at 2 wt. % and 5 wt. % in poly etheretherketone (2Gn-PEEK and 5Gn-PEEK). The morphology, structure, thermal properties, and mechanical properties of PEEK, 2Gn-PEEK and 5 Gn-PEEK were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), flexural mechanical testing, and dynamic mechanical analysis (DMA). Addition of graphene to PEEK induces surface crystallization, increased percent crystallinity, offers a composite that is thermally stable until 550 °C and enhances thermomechanical properties. Results show that graphene was successfully melt-blended within PEEK using this method.

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Fiber-reinforced polymer matrix composites offer lightweight, high mechanical performance but have required much effort to achieve good fiber-matrix adhesion and uniform distribution, and generally suffer from low impact resistance. In this work, a uniform, high shear melt-processing method was used to prepare carbon fiber (CF) reinforced polyetheretherketone (PEEK), carbon nanofiber (CNF) reinforced PEEK, and multi-scale CF and CNF reinforced PEEK composites. Scanning electron microscopy images show good fiber distribution and fiber-matrix interaction, as well as surface crystallization of PEEK from the fiber surfaces. Tensile modulus and strength increase most significantly with the addition of CF but with a loss in ductility. The multi-scale composite of CF-CNF-PEEK displays the stiffening effect from the CF and retains more ductility due to the CNF. Further, the CF-CNF-PEEK composite displays the highest impact energy absorption. This study shows that good mixing of CFs and CNFs is achievable in PEEK using a uniform, high shear processing method that can easily produce intricate shapes and provides a stiff, high impact energy absorption multi-scale carbon fiber-reinforced composite.