xinfeng ouyang ¹ guojie ge ² yizhi geng ¹ yangyang zong ¹ tong pan ² xiao wang ² weiwei zhu ² yuefeng bai ¹ yunpeng liu ¹ shuo duan ¹ kangmin niu ^1*

• ¹ University of Science and Technology Beijing, Beijing, China
• ² zhognfushenying caibon fiber Company Limited, lianyungang, China

The present study involves the preparation of continuous carbon fiber samples treated with epoxybased sizing agent(EP) and vinyl ester resin-based sizing agent (VE), alongside untreated fibers. Surface analysis, including Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM), and X-ray Photoelectron Spectroscopy (XPS), was conducted to characterize the surface state, followed by testing the mechanical properties of the composite materials. Results indicate that, compared to unsized carbon fibers, EP and VE increase the O atom content on the carbon fiber surface by 13.0% and 18.1%, respectively, and enhance the proportion of active C atoms by 11.3% and 20.3%, respectively. The interlaminar shear strength (GB/T) of carbon fibers is improved by 9.3% and 20.0%, respectively. VE demonstrates superior performance over EP in regulating the interface state of carbon fibers. The increased number of active functional groups at the interface results in a higher degree of chemical bonding between the fiber surface and the resin, ultimately enhancing the interlaminar shear strength of carbon fiber composites. Further analysis reveals that, given the compatibility between the sizing agent and the matrix resin, VE improves the open-hole compressive strength of composites by 6.7% compared to EP. This improvement in interface bonding performance positively impacts the open-hole compressive properties of the composites, though it has limited effect on the 0° compressive and post-impact compressive strengths. Following EP and VE sizing, the 0° compressive strength increases by 11.8% and 13.6%, respectively, with VE only resulting in a marginal 1.6% improvement over EP. The presence or absence of a sizing agent has a more significant impact on the compressive properties of carbon fiber composites than the type of sizing agent used. These findings provide valuable insights for optimizing the preparation and enhancing the compressive performance of carbon fiber composite materials.