Kevlar49单丝和单束的随机破坏及有限元模拟

为研究不同尺度下Kevlar49单丝(微观)和单束(细观)的拉伸力学性能,首先,分别采用MTI微型拉伸试验机和MTS微机控制电子万能试验机对纤维丝和纤维束进行了单向拉伸试验,发现纤维丝和纤维束的力学性能与试样的标距及结构尺度存在很大相关性,试样的拉伸强度会随着其标距的增加和结构尺度从纤维丝增大到纤维束而降低;随后,按照Weibull分布对试验数据进行统计分析,量化了不同标距下纤维丝和纤维束拉伸强度的随机变化程度;接着,考虑到纤维丝的拉伸强度符合Weibull分布随机破坏,利用ANSYS中的用户自定义子程序(USERMAT)建立了纤维丝本构模型;最后,采用纤维丝本构模型模拟纤维束的拉伸破坏行为,并讨论了关键参数对纤维束拉伸破坏行为的影响。结果表明:纤维束的模拟结果与试验结果吻合程度较好,所建模型可以较准确地预测纤维束的拉伸性能。 

Probabilistic failure and finite element simulation of Kevlar 49 single filament and single yarn

In order to investigate the tensile mechanical properties of Kevlar 49 single filament (microcosmic) and single yarn (mesoscopic), MTI miniature tensile tester and MTS microcomputer control electron universal testing machine were used respectively to conduct the unidirectional tensile tests on filament and yarn firstly, and found that there was a significant correlation between the mechanical properties of filament and yarn as well as gauge length and structural length scale of samples. The tensile strength of samples decreased with the increasing gauge length and structural length scale enlarged from filament to yarn. Then, the testing data was statistically analyzed according to Weibull distribution, and the random variability degree for tensile strength of filaments and yarns under different gauge lengths was quantified. After that, for the tensile strength of filament according with the Weibull distribution and probabilistic failure, user-defined subroutine (USERMAT) in ANSYS was used to establish the filament constitutive model. Finally, the filament constitutive model was used to simulate the tensile failure behaviors of yarn, and the effects of key parameters on tensile failure behaviors of yarns were also discussed. The results show that the goodness of fit between simulated results and testing results of yarn is preferable, and the established USERMAT can predict the tensile properties of yarn comparatively accurately.