三维编织复合材料多次应力波冲击损伤特征

Damage Characteristics of 3D Braided Composites Under Multiple Stress Wave Impacts

三维编织复合材料在对结构件重量和冲击强度要求较高的高/低温应用场合,有着比金属材料更明显的性能/重量比优势,在高强度和轻量化零部件设计中有极大应用潜力。采用高速摄影记录冲击变形过程,用试验测试和有限元分析方法,研究三维碳纤维增强环氧树脂编织复合材料在不同环境温度单次与多次应力波加载下的横向冲击损伤性质,揭示横向冲击加载下的热力耦合损伤机制。研究发现,在单次应力波加载下,复合材料冲击面的压缩应力大于背部的拉伸应力;而在多次应力波加载下,随着试件变形背部的拉伸应力逐渐增大,大于冲击面的压缩应力。在室温下,复合材料的绝热温升集中在断裂面;而在高温下复合材料韧性增强,基体与增强体热膨胀系数的差异导致环氧树脂和碳纤维束相互挤压,绝热温升分布受编织结构的影响,表面呈散点状分布。研究表明,编织复合材料在室温和高温下的冲击损伤结构设计,为促进编织复合材料在冲击工程结构设计等领域的应用提供了理论依据。

Three-dimensional(3D) braided composites have obvious advantages over metal materials in high and low temperature environments in which the high ratio of strength/weight is required. Currently the 3D braided composites have been widely applied to the design of high strength and lightweight engineering structures. In this paper, the high-speed camera was used to record the impact deformation process. A split Hopkinson pressure bar and finite element analysis have been employed for studying the single and multiple transverse impact damage behaviors of 3D carbon fiber reinforced epoxy resin braided composites at different ambient temperatures, revealing the thermo-mechanical coupling damage mechanisms under transverse impact loading. We found that the compressive stress on the impact surface of the composite is greater than the tensile stress on the back during single impact pulse, while the tensile stress on the back increases gradually with the deformation of the specimen during multiple impact pulses, which is greater than the compressive stress on the impact surface. The adiabatic temperature rise of the composite is concentrated on the fracture surface at room temperature, while at 210 ℃, the toughness of the composite is enhanced, and the difference of thermal expansion coefficient between matrix and reinforcement leads to the mutual extrusion between epoxy resin and carbon fiber tows. The adiabatic temperature rise is affected by the braided structure, and the surface presents a scattered-shape distribution. The results provide a theoretical basis for the impact damage structural design of braided composites at room and high temperatures, and promote the application of braided composites in the impact engineering structural design and other fields.