Enhanced Interfacial Properties of High-Modulus Carbon Fiber Reinforced PEKK Composites by a Two-Step Surface Treatment: Electrochemical Oxidation Followed by Thermoplastic Sizing

Abstract

A two-step surface treatment was conducted on high strength and high modulus carbon fibers (HSHM-CFs) to enhance the interfacial properties of polyetherketoneketone (PEKK) matrix composites. In the two-step surface treatment, the surfaces of HSHM-CFs were electrochemically oxidized followed by sizing treatment. Thermoset epoxy (EP) sizing agents and thermoplastic polyetherimide (PEI) sizing agents were utilized for comparison. Results showed that PEI sizing agents had better wetting effects than EP sizing agents. The sizing process led to increases in fiber strength due to healed surface flaws and inhibited micro-crack initiation. Although EP sizing agents were incompatible with PEKK matrix, the interlaminar shear strength (ILSS) of PEKK matrix composites reinforced by EP-sized fibers still increased, compared with that by untreated fibers, due to hydrogen bond and weak chemical reactions between HSHM-CFs and PEKK matrix. The strong interaction between PEI sizing agents and HSHM-CFs, diffusion and entanglement as well as the noncovalent π-π interaction between PEI sizing agents and PEKK matrix resulted in highest ILSS value of PEI-sized HSHM-CF/PEKK composites.

Thermally conditioned aerospace‐grade carbon fiber reinforced polyether ketone ketone composites: Structure, impact response, and thermomechanical performance

“…C1s spectra of CF/PEKK composites were resolved into four individual peaks at 284.40–285.13, 286.05–287.32, 288.99–291.53, and 292.95 eV, which correspond to CC/CH; CO; CO; and OCO, respectively. [ 34–36 ] After thermal conditioning, CO bond intensity increased while CO bond intensity decreased (Table 4). The CO (COH and COR) and OCO (COOH and COOR) bonds relate to the functionality of the surface, and the structural change is primarily characterized by CO bonds (Figure 1).…”

“…The high-resolution XPS spectra results are given in Figures 7 and 8 and Tables 4 and 5. The peaks at 284.43- [34][35][36] After thermal conditioning, C O bond intensity increased while C O bond intensity decreased (Table 4). The C O (C OH and C OR) and O C O (C OOH and C OOR) bonds relate to the functionality of the surface, and the structural change is primarily characterized by C O bonds (Figure 1).…”

Construction of Polar Functional Groups on the Surface of a High-Modulus Carbon Fiber and Its Effect on the Interfacial Properties of Composites

“…This method can produce relatively well-distributed oxygen-containing functional groups on the surface of carbon fibers and effectively improve the interfacial bonding strength of carbon fiber–resin matrix composites. Studies − have shown that when the tensile modulus of a carbon fiber does not exceed 350 GPa, the graphitization degree of the carbon fiber surface is relatively low, and the effect of this surface treatment is better. Sun used ammonium bicarbonate as the electrolyte to continuously anodize the T300-grade carbon fiber, and the interfacial shear strength (IFSS) between the carbon fiber and the resin matrix increased to about 80 MPa.…”