关键词: 复合材料, 废弃预浸料, 回收, 增韧, 力学性能

Abstract: "Carbon fiber-reinforced resin matrix composites, with their excellent mechanical properties, show a wide range of application prospects in high-end fields such as aerospace and civil manufacturing. Carbon fiber prepreg, as the core intermediate raw material, produces a large amount of waste trimmings during the composite preparation process due to cutting and processing. The traditional recycling technology has technical bottlenecks such as the difficulty of resin decomposition, the serious pollution of chemical treatment, and the high energy consumption of pyrolysis, which leads to a large number of high-performance materials being discarded. In this regard, a closed-loop recycling scheme based on physical reconstruction was proposed to provide a new paradigm for the whole life cycle of carbon fiber composites. Waste prepregs from aerospace manufacturing were used as raw materials, and three characteristic sizes (20-20, 30-30, and random sizes) of fragment units were obtained by ultrasonic vibration dispersion, and the recycled laminates were prepared by hot pressing. To break through the limitation of physical reconfiguration performance, the innovative mechanism of short-cut carbon fiber toughening was introduced, and two lengths of short fibers were embedded between the layers to construct a multi-stage reinforcement system. The three-point bending and quasi-static compression tests combined with X-ray tomography were used to investigate the synergistic effect of fragment size on the length of toughened fibers. The experimental results show that the fragment size has a significant effect on the mechanical properties of the regenerated plywood: 30-30 size regenerated plywood has the best bending and compression properties, while 20-20 size is the worst, with less than half of the mechanical properties of normal plywood. Comparison of recycled plywood toughened with short-cut carbon fibers shows that the bending and compression properties of the toughened recycled plywood are significantly improved. The most significant improvement in bending performance is found in the regenerated plywood toughened with 6 mm chopped carbon fiber. The compressive properties of the regenerated laminates toughened with 10 mm chopped carbon fibers are the most significantly improved. Micro tomographic analysis reveals that the short-cut carbon fibers are attached at the end of the matrix crack, and the toughened fibers form a 'fiber bridging' structure at the crack tip. The fiber pull-out phenomena occurrs when the external load is applied to the specimen. Due to the bonding effect between the fibers and the matrix, the energy of crack extension is absorbed and the crack extension is effectively suppressed, and the catastrophic failure triggered by interfacial debonding is effectively suppressed by such a multiscale enhancement mechanism. It has been experimentally confirmed that through the synergistic design of physical reconstruction and fiber toughening, the bending and compression properties of regenerated laminates from waste prepregs can be restored to more than 74.74% and 66.17% of the normal original materials, respectively, which provides a technological path for the closed-loop recycling of carbon fiber-reinforced composites that combines both economic and environmental benefits."

Key words: CFRP, waste prepreg, recycling, toughening, mechanical preference