Fatigue and creep of high-performance fibers: Deformation mechanics and failure criteria

This paper shows the longitudinal failure of the high-performance fiber having structural extended chain conformation follows a failure criterion based on critical strain. There is a universal critical strain at which fibers fail under fatigue and creep loading as well as under tensile loading. It is speculated that the failure of these high performance fibers is dominated by shear deformation for different loading conditions. The fiber develops permanent deformation under fatigue or creep. The permanent deformation is determined by the applied loading condition and the time of the loading. Two material constants are derived to characterize the fiber deformation under loading and thus the material resistance to external loading: the creep strength and creep strength index for creep loading and the fatigue strength and fatigue strength index for fatigue loading, respectively.