  We study the creep rupture of fiber composites in the framework of fiber
bundle models. Two novel fiber bundle models are introduced based on different
microscopic mechanisms responsible for the macroscopic creep behavior.
Analytical and numerical calculations show that above a critical load the
deformation of the creeping system monotonically increases in time resulting in
global failure at a finite time $t_f$, while below the critical load the system
suffers only partial failure and the deformation tends to a constant value
giving rise to an infinite lifetime. It is found that approaching the critical
load from below and above the creeping system is characterized by universal
power laws when the fibers have long range interaction. The lifetime of the
composite above the critical point has a universal dependence on the system
size.
