On the Creep Rupture Prediction of Composite Pressure Vessels

This article illustrates a concept of predicting the time dependent deformation and creep rupture strength of carbon fibre reinforced plastics (CFRP). In the presented concept the viscoelastic behaviour of the resin is determined by creep rupture tests at different temperature and load levels. Out of the experiments the relaxation spectrum of the resin is modelled including the spread. With the help of the classical rule of mixture and a modified classical laminate theory the minimum strain rate for the composite will be determined. The results will be compared to experimental data. Furthermore the Monkman-Grant approach is used to determine the time-to-failure strain-rate relation. Therefore an elastic solution of the classical laminate theory is used including Puck’s failure criteria to compute the Monkman-Grant relation. A Monte Carlo Simulation will be done to include the spread of the Monkman-Grant relation. The results will be compared to experimental results of unidirectional specimens. Finally it will be explained how the lifetime of a pressure vessel can be computed using the explained concept.