Biaxial shear/tension failure behavior of Spectra single fibers

An experimental study is conducted to develop the biaxial failure surface of single Spectra 100d and Spectra 130d filaments in a torsion-tension environment. The cross-sectional profiles of single fibers are evaluated using scanning electron microscopy and X-ray computed tomography. In efforts to hold the polyethylene single fiber, a pin-gripping method is developed. Effects of pin diameter on failure stress for both Spectra types are characterized. Additionally, the effect of sample gauge length on fiber tensile strength is investigated. Quasi-static experiments are conducted using an MTS servo-hydraulic system to apply tensile loads on pre-twisted single fibers. A tension Kolsky bar is employed to study the biaxial shear/tensile behavior of single fibers at high strain-rates. A decreasing trend of tensile strength with increasing torsional strain is observed for both Spectra 100d and 130d. Furthermore, a torsional pendulum apparatus is used to determine the apparent torsional shear stresses in pre-twisted fibers at various levels of axial loading and a relationship between apparent shear stress and axial stress is developed. Finally, a biaxial shear/tension failure envelope of each fiber type is established.