Defect effects of carbon fiber composites under dynamic impact conditions are important to mechanical behavior design in the aerospace field. Here we report the defect effect on the impact compressive behavior of 3D braided composites at high strain rates from 550/s to 1240/s. The defect effect on damage behavior was observed by high-speed photography and digital image correlation (DIC) technology. A finite element analysis (FEA) model was developed to show the defect effect on stress distribution and thermo-mechanical behavior. The defect structure reduces the compressive strength of the composite and causes more brittle and catastrophic failure compared with the perfect composite. The defect effect on the compressive behaviors is more significant at higher strain rates. FEA results show that the defect structure causes local stress concentration, high adiabatic temperature rise, and high stress in the X-shaped shear band region, thereby accelerating composite failure.

中文翻译：

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缺陷对 3D 编织复合材料高应变率压缩行为的影响

碳纤维复合材料在动态冲击条件下的缺陷效应对于航空航天领域的力学行为设计具有重要意义。在这里，我们报告了缺陷对 3D 编织复合材料在 550/s 至 1240/s 的高应变率下的冲击压缩行为的影响。通过高速摄影和数字图像相关（DIC）技术观察缺陷对损伤行为的影响。开发了有限元分析 (FEA) 模型来显示缺陷对应力分布和热机械行为的影响。与完美的复合材料相比，缺陷结构降低了复合材料的抗压强度，并导致更多的脆性和灾难性故障。缺陷对压缩行为的影响在较高应变率下更为显着。有限元分析结果表明，缺陷结构导致局部应力集中、绝热温升高、X形剪切带区域应力高，从而加速复合材料失效。