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<p>This study investigates the dynamic compressive mechanical properties and failure mechanisms of three-dimensional five-directional braided carbon/epoxy composites under both ambient and thermal degradation conditions. Dynamic impact tests were conducted at various strain rates using a split Hopkinson pressure bar. The results show a strong positive correlation between peak stress and strain rate, indicating a strain-rate sensitivity. The observed failure modes also depended on strain rate: at low strain rates, failure primarily involved fiber fracture and shear fracture; at medium strain rates, fiber dislocation and minor matrix cracking appeared; and at high strain rates, severe matrix cracking, extensive fiber fracture, and significant fiber-bundle loosening occurred. A macroscopic equivalent damage constitutive model incorporating a damage evolution criterion was established to simulate this behavior, and the simulation results agreed well with experimental data. After thermal exposure (200 °C, 230 °C, and 260 °C for 2 h), the composites exhibited significant matrix softening, with carbonization evident at 260 °C. The post-thermal stress–strain curves showed pronounced nonlinearity and plastic failure. Notably, overall damage severity—including increased fiber dislocation, fiber fracture, matrix cracking, and debonding—escalated with increasing exposure temperature, directly linking thermal degradation to worsened dynamic performance.</p>

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Mechanisms of Dynamic Compressive Damage and Post-thermal Degradation in 3D5d Braided Composites

  • 期刊论文

  • 发表日期：

    2026年3月3日

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  • Yong Chen,
  • Zhiruo Chen,
  • Du Huang,
  • Shaowei Zhu,
  • Jiayong Zhou,
  • Liming Chen,
  • Xuejuan Tao,
  • Juncen Du

摘要

This study investigates the dynamic compressive mechanical properties and failure mechanisms of three-dimensional five-directional braided carbon/epoxy composites under both ambient and thermal degradation conditions. Dynamic impact tests were conducted at various strain rates using a split Hopkinson pressure bar. The results show a strong positive correlation between peak stress and strain rate, indicating a strain-rate sensitivity. The observed failure modes also depended on strain rate: at low strain rates, failure primarily involved fiber fracture and shear fracture; at medium strain rates, fiber dislocation and minor matrix cracking appeared; and at high strain rates, severe matrix cracking, extensive fiber fracture, and significant fiber-bundle loosening occurred. A macroscopic equivalent damage constitutive model incorporating a damage evolution criterion was established to simulate this behavior, and the simulation results agreed well with experimental data. After thermal exposure (200 °C, 230 °C, and 260 °C for 2 h), the composites exhibited significant matrix softening, with carbonization evident at 260 °C. The post-thermal stress–strain curves showed pronounced nonlinearity and plastic failure. Notably, overall damage severity—including increased fiber dislocation, fiber fracture, matrix cracking, and debonding—escalated with increasing exposure temperature, directly linking thermal degradation to worsened dynamic performance.