三维编织碳纤维/环氧复合材料的吸湿特性及外应力的影响

采用真空浸渍法制备了三维编织碳纤维增强环氧树脂(C_3D/ER)复合材料,研究了该复合材料的吸湿特性及外应力的影响。讨论了应力对C_3D/ER复合材料吸湿行为的作用机理。 结果表明,与环氧树脂不同,C_3D/ER复合材料的吸湿行为不能用Fick第二定律描述。外应力可加速吸湿初期复合材料的吸水和力学性能的下降,但可降低复合材料平衡吸湿量和最终力学性能的下降幅度。分析表明,吸湿过程中C_3D/ER复合材料力学性能的高低取决于其吸湿量的大小。

MOISTURE ABSORPTION BEHAVIOR OF 3-D CARBON-FIBER-EPOXY COMPOSITES AND EFFECT OF EXTERNAL STRESS

Three-dimensionally (3-D) braided carbon fiber reinforced epoxy resin (C3D/ER) composites were produced by vacuum impregnation technique. The present study is carried out in order to determine the water absorption characteristics of the 3D composites. In addition, the influences of the external load on the water uptake and changes in the flexural, shear and impact strengths were also determined as a result of moisture absorption. The kinetics of moisture absorption by the stressed and unstressed composites, as well as the unreinforced epoxy resin, was determined for the absorption at 37 ℃±0.5 ℃. The results show that the C3D/ER composites exhibited a complicated absorption behavior. In contrast to the epoxy resin, the absorption behavior of the C3D/ER composite could not be described by using Fick's law of diffusion. The results clearly demonstrate the contribution of the external stress to the water absorption behavior and changes in mechanical properties. The external stress was found to increase the moisture content and mechanical properties reduction at earlier stages. At later stages, a contrary trend was observed. It is concluded that the mechanical properties are proportional to their moisture content for the C3D/ER composites. Mechanisms were proposed to interpret these experimental phenomena.