Improvement of interfacial properties and hygrothermal resistance of CF reinforced epoxy composites by fluorine-containing sizing agent

Abstract

To enhance the interfacial bonding performance between carbon fibers (CFs) and epoxy resin, the fluorine-containing sizing agent was prepared by the unique characteristics of fluorine. The incorporation of C-F bonds endows the interfacial layer with a higher degree of homogeneity, effectively mitigating stress concentrations that arise from surface imperfections. This mitigation is attributed to the repulsive interactions among fluorine atoms. The test results showed that the interlaminar shear strength (ILSS) of carbon fiber reinforced epoxy composites (CFREs) can be increased to a maximum of 66.01 MPa, representing a notable enhancement of 15.79 % in comparison to unsized CFREs. The enhancement of interfacial bonding ability is primarily ascribed to the synergistic effects of mechanical interlocking and chemical bonding interactions at the interface between CFs and resin. Concurrently, the hygrothermal resistance of CFREs was subjected to rigorous testing. The electron cloud of fluorine atoms exerts a pronounced shielding effect on the carbon chains, thereby significantly bolstering the hygrothermal resistance of CFREs. This enhancement is critical for the CFREs ' application in environments with high humidity and temperature. Moreover, the sizing agent developed in this study boasts a streamlined production process, which is expected to be applied in the commercial large-scale production of CFs.