Abstract To understand the strain rate sensitivity of carbon/carbon (C/C) composite pins’ shear behaviors, quasi-static and dynamic experiments are conducted using an electric universal testing machine and a drop weight impact testing machine. A scanning electron microscope (SEM) is used to observe the shear fracture surfaces. The results show that the shear failure stress increases with increasing strain rate. Under quasi-static loading, the C/C composites damage with fibers fracture successively, and the shear stress-strain curve shows a “pseudo-plastic” characteristic, while brittle fracture features subjected to dynamic loading. In order to explain such differences, a viscoelastic constitutive model incorporated with a damage model based on the Weibull distribution function is proposed. Parameters of the constitutive model are estimated based on the experimental data. After that, the theoretical shear failure stresses are obtained by calculating the maximum shear stress of the constitutive model for different shear strain rates. The fitted model and theoretical failure stress match well with the experimental data.

中文翻译：

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碳/碳复合材料销钉的动态剪切断裂行为和“伪塑性”本构模型

摘要 为了了解碳/碳（C/C）复合材料销钉剪切行为的应变率敏感性，利用电动万能试验机和落锤冲击试验机进行了准静态和动态实验。使用扫描电子显微镜（SEM）观察剪切断面。结果表明，剪切破坏应力随着应变速率的增加而增加。在准静态加载下，C/C复合材料连续损伤，纤维断裂，剪切应力-应变曲线呈现“假塑性”特征，而在动态加载下呈现脆性断裂特征。为了解释这种差异，提出了一种粘弹性本构模型，该模型与基于威布尔分布函数的损伤模型相结合。本构模型的参数是根据实验数据估计的。之后，通过计算不同剪切应变率下本构模型的最大剪切应力，得到理论剪切破坏应力。拟合模型和理论破坏应力与实验数据吻合良好。