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| Damage Characteristics of 3D Braided Composites Under Multiple Stress Wave Impacts |
| HU Meiqi, SUN Baozhong, GU Bohong |
| Donghua University, Shanghai 201620, China |
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Abstract 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.
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2022, 
