▎ 摘　　要

The effect of thermo-oxidative aging on the vibration damping characteristics of the conventional fabric composites reinforced by three-dimensional (3D) and four-directional (4Dir) braided preform and laminated plain woven fabric and the 3D-4Dir braided graphene-based carbon fiber composites was investigated. Specimens were isothermally aged at 140 degrees C for various periods of time up to 1,200 h. The results indicated that the thermo-oxidative aging resulted in deterioration of the matrix and interface performance, in the form of chain scissions, weight loss, microcracks and interfacial debonding, which should be responsible for the decrease of nature frequency and the increase of damping coefficient of the composites. After aging for 1,200 h, the first nature frequency and first damping coefficient retention rates of 3D-4Dir braided graphene-coated carbon fiber/epoxy composite were 5.5% and 6.4% higher than those of laminated composite, respectively. One of the reasons was the integrated structure of 3D-4Dir braided composite exposed lower fiber end area to air than that of laminated composite, leading to less interface oxidation. Another reason was that the graphene reinforced gradient interphase provided an effective shield against interface oxidation and restricted the movement of the different phase of the materials at the composites interface. This synergetic reinforcing effect of 3D-4Dir braided structure and graphene reinforced hierarchical interface provides an easy and effective way to design and improve the thermo-oxidative stability of carbon fiber reinforced polymer composites. (C) 2015 Society of Plastics Engineers