单纤维微拉伸力学性能测试与分析

针对微尺度材料力学性能测试与尺度效应实验研究的需要,自行研制了一台FMT-I型高精度纤维材料微拉伸力学性能实验装置,并基于LabVIEW软件平台开发了相应的数据采集与控制系统,实现了测试过程的全自动化。该装置的测力传感器由非接触式激光位移传感器和两端固定的薄梁组成,可同时测量试样的拉伸力和上夹持端的位移量,帮助精确地获取试样的载荷-变形曲线。采用该装置对微米级直径的多晶铜丝、316L不锈钢纤维和T300碳纤维进行了拉伸测试。实验结果表明,直径为18～105μm多晶铜丝的拉伸力学行为并无明显的尺度效应;多晶铜丝和316L不锈钢纤维的弹性模量分别在43.9～60.0GPa和102.9～111.5GPa之间,均低于宏观尺度下材料的弹性模量;316L不锈钢纤维的抗拉强度和延伸率随着丝径的减小而降低;T300碳纤维的弹性模量为235.4±12.4GPa,抗拉强度为3238.2±280.8MPa,断裂应变约为1.5%。另外,相同的细铜丝材料的测试结果与Instron5848型商用拉伸试验机的测试结果进行了对比,吻合良好。通过系统的实验分析表明,该装置具有较高的精度和稳定性,适用于各种纤维材料的拉伸力学性能测试。

On the Mechanical Properties in Micro-Tensile Testing of Single Fiber

In order to measure the mechanical properties and investigate the size effect experimentally,a high accuracy fiber micro-tensile tester(FMT-I) was developed.Corresponding data acquiring and operating system was also designed based on LabVIEW.Load cell of the tester consists of a noncontact type laser displacement sensor and a thin beam fixed at both ends,which is used to measure both tensile force acted on sample and the displacement of upper gripper,so force-displacement curve of sample may be obtained accurately.Tensile tests for micro-sized polycrystalline copper wire,316L stainless steel fiber and T300 carbon fiber were performed by using the tester.Experimental results show that(i) there is no significant size effect in tensile response of polycrystalline copper wire with diameter ranging 18-105μm;(ii) Young’s modulus of polycrystalline copper wire and 316L stainless steel fiber is in the range 43.9-60.0GPa and 102.9-111.5GPa,respectively,which are smaller than their bulk values;(iii) both ultimate strength and elongation of the 316L stainless steel fiber are decreased with the diameter decreasing;(iv) Young’s modulus and the ultimate strength of carbon fiber are 235.4±12.4GPa and 3238.2±280.8MPa,respectively,and their fracture strains are about 1.5%.Moreover,the measured results of same type samples agree well with that obtained by using commercial Instron 5848 microtester.The micro-tensile tester presented in this paper has high precision and good stability and can be used to measure the tensile properties of various fibrous materials.