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<p>Tailoring the meso-structural parameters of braided composites offers a proactive strategy to optimize their damage modes and energy dissipation mechanisms under low-velocity impact. This paper systematically investigates the effect of the fiber bundle aspect ratio, as a key mesostructural design parameter, on the impact performance of braided composites. In this study, three types of laminates with different aspect ratios were fabricated by varying the braiding mandrel radius and were tested under impact energies of 20&#xa0;J, 30&#xa0;J, and an energy level adjusted to eliminate the effect of thickness. The results show that the high-aspect-ratio specimen exhibited a higher peak load and was not perforated, whereas the low-aspect-ratio specimen underwent perforation failure, indicating a significant enhancement in its impact resistance. Damage mechanism analysis reveals that the fiber bundle aspect ratio directly determines the single-ply thickness and crimp angle of the yarns: the large crimp angle caused by a low aspect ratio induced severe interlaminar shear stress under impact, promoting early and extensive delamination as the dominant failure mode. Conversely, the lower crimp angle in the high-aspect-ratio specimen effectively suppressed delamination, compelling the system to dissipate energy through the higher energy-threshold mechanism of bottom-ply tensile fiber fracture. This fundamental shift in the damage mode, from delamination-dominated to fiber-fracture-dominated, was corroborated at both macro- and meso-scales using quasi-static indentation (QSI) tests and X-ray micro-computed tomography (µ-CT). This study confirms that actively controlling the dominant failure mode by tailoring the fiber bundle aspect ratio is an effective strategy for enhancing the impact damage tolerance of braided composites.</p>

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The Effect of Fiber Bundle Aspect Ratio on the Low-Velocity Impact Performance and Damage Mechanism of Carbon Fiber Braided Composites

  • 期刊论文

  • 发表日期：

    2026年1月14日

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  • Zhenyu Wu,
  • Shaojie Zhang,
  • Kehong Zheng,
  • Lin Shi,
  • Wenkai Fan,
  • Yuhang Zhang

摘要

Tailoring the meso-structural parameters of braided composites offers a proactive strategy to optimize their damage modes and energy dissipation mechanisms under low-velocity impact. This paper systematically investigates the effect of the fiber bundle aspect ratio, as a key mesostructural design parameter, on the impact performance of braided composites. In this study, three types of laminates with different aspect ratios were fabricated by varying the braiding mandrel radius and were tested under impact energies of 20 J, 30 J, and an energy level adjusted to eliminate the effect of thickness. The results show that the high-aspect-ratio specimen exhibited a higher peak load and was not perforated, whereas the low-aspect-ratio specimen underwent perforation failure, indicating a significant enhancement in its impact resistance. Damage mechanism analysis reveals that the fiber bundle aspect ratio directly determines the single-ply thickness and crimp angle of the yarns: the large crimp angle caused by a low aspect ratio induced severe interlaminar shear stress under impact, promoting early and extensive delamination as the dominant failure mode. Conversely, the lower crimp angle in the high-aspect-ratio specimen effectively suppressed delamination, compelling the system to dissipate energy through the higher energy-threshold mechanism of bottom-ply tensile fiber fracture. This fundamental shift in the damage mode, from delamination-dominated to fiber-fracture-dominated, was corroborated at both macro- and meso-scales using quasi-static indentation (QSI) tests and X-ray micro-computed tomography (µ-CT). This study confirms that actively controlling the dominant failure mode by tailoring the fiber bundle aspect ratio is an effective strategy for enhancing the impact damage tolerance of braided composites.