Damage-enhanced creep and rupture in fiber-reinforced composites
The time-dependent deformation of uniaxial composites reinforced with continuous stochastic fibers is examined using a one-dimensional model of a viscoelastic-plastic matrix reinforced with continuous viscoelastic fibers. The important effect of successive fragmentation of the stochastic fibers under increasing load is included using a nonlinear constitutive model of the fiber bundle deformation which accurately includes the stochastic failure of fibers and the influence of fiber/matrix slip around fiber breaks. Matrix yielding and/or cracking are also incorporated into the model. Detailed analyses of three special cases particularly applicable to metal and ceramic composites are presented: a viscoelastic-plastic matrix reinforced (i) with elastic fibers and subjected to a step tensile loading; (ii) with elastic fibers and stretched at a constant rate of extension; and (iii) with viscoelastic fibers and subjected to a step tensile loading. Comparisons of the predicted deformations to recent experimental data on titanium matrix composites show reasonable agreement in the creep rates, failure times and general deformation history. Copyright (C) 1996 Acta Metallurgica Inc.