关键词: 复合材料修复, 树脂预涂层, MWCNTs-NH2桥接, 毛细作用

Abstract: "Carbon fiber/glass fiber composite laminates, by synergistically leveraging the high strength of carbon fibers and the toughness of glass fibers, are widely used in aerospace, new energy vehicles, and other fields. However, during practical applications, these materials often suffer from damage such as delamination and cracks due to complex loads like impact and vibration. Directly replacing damaged components is costly and not environmentally friendly, making the development of effective repair technologies critical. Among existing repair methods, external repair techniques are more suitable for engineering applications due to their simplicity and high reliability, mainly including three categories: patch repair, resin injection, and resin pre-coating (RPC).The RPC technique involves coating a low-viscosity repair solution (a mixture of epoxy resin and acetone) onto the damaged surface. The capillary action of acetone is utilized to infiltrate the epoxy resin into internal defects, and structural repair is completed after curing. Introducing carbon nanotubes (CNTs) into the repair liquid can further enhance the mechanical properties of the repair interface. This study proposes the use of aminated carbon nanotubes (MWCNTs-NH2) reinforced RPC technology. Compared to traditional acetone solvents, ethyl acetate serves as a more environmentally friendly alternative solvent, and the addition of MWCNTs-NH2 can effectively strengthen the interfacial bonding. The study employs an autoclave process to prepare carbon/glass laminate samples and prefabricates standardized crack damage through three-point bending tests. It focuses on analyzing the repair mechanism of MWCNTs-NH2 reinforced RPC and investigating the influence of parameters such as resin mass fraction, carbon nanotube addition amount, repair temperature, and repair duration on the compressive strength recovery rate. Results show that the resin pre-coating solution containing MWCNTs-NH2 exhibits significant repair effects. During the 8-day repair period, its performance is significantly better than that of the control group without added carbon nanotubes. Moreover, the repair effect improves with an increase in the mass fraction of MWCNTs-NH2. When the ratio is 10% RPC + 3wt% MWCNTs-NH2, the compressive strength increases by 30% compared to the original sample. An excessively high resin mass fraction (such as 30% RPC) can suppress the repair effect. An increase in repair temperature can accelerate the curing reaction, with repair efficiency significantly improving to 93% from 25 °C to 70 °C. However, 70 °C can easily lead to incomplete curing, resulting in localized stress concentration and a significant decrease in sample stiffness. Extending the repair duration allows for more thorough resin curing, with the compressive strength increasing by 100% under a 60-day repair period compared to an 8-day repair sample. Observation results from computed tomography (CT) technology show that the pre-coating solution doped with MWCNTs-NH2 can effectively fill cracks and reduce their width, further confirming the repair effect. The repair method proposed in this study circumvents the fiber-matching limitations of patch repair and the secondary damage issues of resin injection, aligning with the repair requirements of carbon/glass composite laminates and demonstrating significant application value."

Key words: composite repair, resin pre-coating, MWCNTs-NH2 bridging, capillary action