Edge-on impact damage of composite structures has drawn significant attention from the engineering and academic communities because of the much more notorious damage caused than that by out-of-plane impacts. However, research focusing on improving the edge-on impact resistance of these structures has been limited. This paper proposed a synergistic toughening approach involving multi-scale carbon nanofiber (CNF) and Z-pin to improve the composite laminates' edge-on impact damage resistance. Through analysis of mechanical response, C-scan, optical and Scanning electron microscopy (SEM) photographs of unreinforced, CNF-reinforced, Z-pin-reinforced and CNF/Z-pin-reinforced laminates, the failure mechanisms of the four types of laminates and the synergistic toughening mechanism of CNF/Z-pin were revealed. The results show that the synergistic toughening of CNF/Z-pin could weaken the negative effects caused by Z-pin implantation and that CNF has the potential to increase the damage initiation energy threshold of the laminate. Furthermore, the toughening effect of Z-pin was significantly greater than that of CNF in damage propagation. Specifically, at 50 J impact energy, the damage area of CNF/Z-pin, Z-pin and CNF-reinforced laminates was reduced by 50.5 %, 39.8 %, and 8.3 %, respectively, compared to unreinforced laminates.

中文翻译：

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使用多尺度 CNF/Z-pin 增韧协同提高复合材料层压板的边缘冲击损伤抵抗能力

复合材料结构的边缘冲击损伤引起了工程界和学术界的高度关注，因为其造成的损伤比面外冲击更为臭名昭著。然而，专注于提高这些结构的边缘冲击抗力的研究仍然有限。本文提出了一种涉及多尺度碳纳米纤维（CNF）和Z-pin的协同增韧方法，以提高复合材料层合板的边缘冲击损伤抵抗能力。通过对未增强、CNF增强、Z-pin增强和CNF/Z-pin增强层压板的机械响应、C扫描、光学和扫描电子显微镜（SEM）照片的分析，四种层压板的失效机制揭示了CNF/Z-pin的协同增韧机制。结果表明，CNF/Z-pin的协同增韧可以减弱Z-pin植入带来的负面影响，并且CNF有可能提高层合板的损伤起始能量阈值。此外，在损伤扩展方面，Z-pin 的增韧效果明显大于 CNF。具体而言，在 50 J 冲击能量下，与未增强层压板相比，CNF/Z-pin、Z-pin 和 CNF 增强层压板的损坏面积分别减少了 50.5%、39.8% 和 8.3%。