关键词: 冲击荷载, 碳纤维掺量, 冲击次数, 纵波波速, 损伤因子, 能量耗散, 扫描电镜

Abstract: In order to study the safety of carbon fiber reinforced high strength concrete under multiple impact loads. The longitudinal wave velocity, damage factor, peak stress and energy dissipation of specimens with different carbon fiber contents (0%, 0.15%, 0.3%, 0.45% and 0.6%) under different impact times (1, 2, 3 and 4) were studied by using a separated Hopkinson pressure bar device with a diameter of 74 mm and a non-metallic ultrasonic testing device. Combined with scanning electron microscope scanning (SEM), the internal microstructure of the specimen under different impact times was observed, and the relationship between the mechanical properties of the specimen and the content of carbon fiber and impact times was analyzed. The results show that the addition of carbon fiber can increase the integrity of the specimen, reduce the internal cracks and increase the longitudinal wave velocity. The first impact will "compact" the internal cracks of the specimen, and the wave velocity of the specimen will increase. With the increase of impact times, the damage degree of the specimen increases and the wave velocity decreases. The addition of carbon fiber can effectively increase the peak stress of the specimen, and the effect is the best when the content is 0.45%. The impact load will cause compaction and damage to the specimen, and the peak stress of the specimen first increases slightly and then decreases greatly. The energy time history change of the specimen under impact load is mainly divided into three stages. The energy dissipation rate of the specimen is the highest when the fiber content is 0.3%. Multiple impact will cause damage accumulation to the specimen, and its energy consumption density will be significantly reduced. SEM test results show that the existence of carbon fiber can effectively reduce the internal crack propagation and the number of cracks under impact load, and the changes of microstructure and macro mechanical properties are consistent.

Key words: impact load, carbon fiber content, impact times, longitudinal wave velocity, damage factor, energy dissipation, scanning electron microscope