Multiscale Viscoelastic Modeling Toward Stress Rupture Prediction of Composite Overwrapped Pressure Vessels

Stress rupture failure in composite overwrapped pressure vessels (COPVs) is a serious concern for vessels that contain fluids under high pressure for long durations. This is especially true for COPVs installed on spacecraft which are designed to low factors of safety to minimize the launch mass but are required to operate for years to decades on orbit and in deep space. Stress rupture failure in COPVs has historically been evaluated using empirical equations that relates fiber strain and load duration to probability of failure. In this paper, a physics-based model of the composite matrix creep is developed to model the strain increase during the stress rupture process. A multiscale modeling approach is used to derive orthotropic viscoelastic properties for a unidirectional composite unit cell. The viscoelastic behavior of composite layups is modeled using finite element models with an Abaqus user subroutine of viscoelastic properties from unit cell model. The capability is demonstrated on a composite laminate and applications to the stress rupture life predictions of COPVs is discussed.