Biaxial Shear/tension Failure Criteria of Spectra Single Fibers

Sun, Jianzhuo. M.S.A.A., Purdue University, May 2014. Biaxial Shear/Tension Failure Criteria of Spectra single fibers. Major Professor: Weinong Chen. An experimental study was conducted to develop the biaxial failure surface criteria of single Spectra 130d and 100d filaments in a torsion-tension environment. The crosssectional profiles of single Spectra fibers were investigated using scanning electron microscopy and X-ray computed tomography. A pin-gripping method to fix the ends of a polyethylene single fiber was developed. Effects of pin diameter on failure stress for both Spectra 130d and 100d were characterized. It was found that the perturbed stress field effect can be neglected when the pin diameter is larger than 0.8 mm. Additionally, the effect of the sample’s gage length on fiber tensile strength was investigated. The gage length of 5.5 mm was determined as an appropriate length for single fiber samples under stress-wave loading. A twisting apparatus was built for a single fiber to achieve specific degrees of shear strains. Quasi-static experiments were conducted using an MTS servo-hydraulic system to apply tensile loads on pre-twisted Spectra fibers. A tension Kolsky bar was employed to study the biaxial shear/tensile behavior of Spectra fibers at high strain rates. A decreasing trend of tensile strength, with increasing torsional strain, for Spectra fibers was observed. Furthermore, a torsional pendulum apparatus was developed to determine the torsional shear stresses in fibers at various levels of axial loading. The relationship between apparent