Creep rupture of viscoelastic fiber bundles.

We study the creep rupture of bundles of viscoelastic fibers occurring under uniaxial constant tensile loading. A fiber bundle model is introduced that combines the viscoelastic constitutive behavior and the strain controlled breaking of fibers. Analytical and numerical calculations showed that above a critical external load the deformation of the system monotonically increases in time resulting in global failure at a finite time t(f), while below the critical load the deformation tends to a constant value giving rise to an infinite lifetime. Our studies revealed that the nature of the transition between the two regimes, i.e., the behavior of t(f) at the critical load sigma(c), strongly depends on the range of load sharing: for global load sharing t(f) has a power law divergence at sigma(c) with a universal exponent of 0.5, however, for local load sharing the transition becomes abrupt: at the critical load t(f) jumps to a finite value, analogous to second- and first-order phase transitions, respectively. The acoustic response of the bundle during creep is also studied.