E玻璃纤维增强环氧树脂基复合材料轴向拉伸力学性能的应变率效应

采用MTS-810材料试验机、Zwick-HTM5020高速拉伸试验机及分离式Hopkinson拉杆（SHTB）实验装置，并结合数字图像相关性（Digital image correlation，DIC）分析方法，对E玻璃纤维增强环氧树脂基复合材料棒材在10^-3~2 400 s^-1应变率范围内的轴向拉伸力学性能进行了较系统的实验研究，获得了不同应变率下材料的应力-应变曲线，揭示了应变率对材料的拉伸强度和断裂应变的影响规律。通过显微分析拉伸试样的断口形貌，揭示了试样的断裂机制及对应变率的依赖性。实验结果表明：E玻璃纤维增强环氧树脂基复合材料的力学性能具有强烈的应变率效应，归一化拉伸强度随着应变率对数线性增加，而归一化断裂应变则随着对数应变率线性减小；断口显微分析显示：E玻璃纤维增强环氧树脂基复合材料的轴向拉伸断裂模式依赖于应变率，低应变率加载下试样发生沿45°方向的剪切断裂，随着应变率增大，试样断裂模式逐渐过渡到沿轴向的拉伸断裂，特别是在高应变加载下，观察到大量的玻璃纤维丝被拉断，同时环氧树脂基体也发生严重的碎裂现象，这反映了基体材料与玻璃纤维之间相互约束作用在增强。

Influence of strain rate on tensile mechanical behavior of E glass fiber reinforced epoxy resin composites

Using MTS-810 material testing machine, Zwick-HTM5020 high speed tensile testing machine and split Hopkinson tension bar (SHTB) apparatus, combined with digital image correlation method, the tensile mechanical properties of the E glass fiber reinforced epoxy resin composites were studied systematically in the range of strain rates of 10^-3-2 400 s^-1.The stress-strain curves under different strain rates were obtained, and the influences of strain rate on tensile strength and fracture strain were investigated. The fracture morphology of the tensile specimen was analyzed, and the dependence of fracture mechanism on the strain rate was explored. The results reveal that the normalized tensile strength increases linearly with the logarithm of strain rate, while the normalized fracture strain decreases linearly with the log strain rate. Fractography shows that the main fracture mode of the specimen is shear fracture along 45° direction at low strain rate. With the increasing of strain rate, the fracture mode gradually transforms shear fracture to axial tensile fracture. At high strain rate, it is observed that a large number of glass fibers are broken, and the epoxy resin matrix has serious fragmentation phenomenon, which reflects the strong restraint effect between the epoxy resin matrix and the glass fiber.