Tensile Strength Statistics and Fracture Mechanism of Ultrahigh Molecular Weight Polyethylene Fibers: On the Weibull Distribution

To study the distribution of ultrahigh molecular weight polyethylene fiber (UHMWPE) strength, three groups of UHMWPE fibers were spun by the gel spinning method, which was undrafted raw fibers (with high strain at break) and fibers with different prespinning and postspinning draw ratios. It is found that even when the strain at break (epsilon(b)) > 46%, the tensile strength of the fiber still obeys the Weibull distribution. The draw ratio has a great influence on the distribution of fiber strength, especially the draw ratios of the spinneret in the prespinning process. It may be that different drafting processes affect the fracture mechanism of the fibers. This paper analyzes and discusses that and proves it by differential scanning calorimetry and the taut tie molecules (TTMs) fractions. The parameters of the Weibull distribution suggest the quality of the fiber. The Weibull modulus is closely related to the dispersion of the fiber properties and processing parameters. The characteristic strength is similar to the test average strength, which is more suitable for the judgment of fiber reliability in actual use. At the same time, the normality of the samples was tested by Kolmogorov-Smirnov, Shapiro-Wilk, Jarque-Bera test, and quantile-quantile (Q-Q) plots, and the strength distribution was visually displayed by the bell curve. The results show that the Gaussian distribution is not so suitable to describe the strength distribution of the stretched fiber compared to the Weibull distribution.