FATIGUE NOTCH SENSITIVITY OF GLASS WOVEN FABRIC COMPOSITES HAVING A CIRCULAR HOLE UNDER TENSION/TORSION BIAXIAL LOADING

Fatigue notch sensitivity of woven fabric composites having a circular hole under tension/torsion biaxial loading was investigated. In-phase (proportional) biaxial stress was applied to tubular specimens. A fatigue notch factor was used to evaluate the fatigue notch sensitivity. The experimental results revealed that the fatigue notch factor was approximately linear with respect to a parameter; cos (tan(-1) alpha) for any fatigue life (alpha is biaxiality ratio of combined stress). The fatigue notch factor decreased with an increase in fatigue life in the case where the shear stress component was relatively small. However, in the case where the shear stress component was large, it increased with an increase in fatigue life. Under pure torsion loading, fatigue damage did not progress along the principal axis. It grew along both longitudinal and transverse fiber bundles. An empirical equation which can easily predict the fatigue notch factor at any arbitrary fatigue life under biaxial loading was proposed. Unknown variables in this equation are determined by fatigue tests under uniaxial tensile and pure torsion loadings.