Lifetime predictions of polymer matrix composites under constant or monotonic load

A revision of long-term lifetime prediction of composite materials under constant and monotonic load is presented. The main failure criteria revised are energy-based criteria and fracture mechanics. It is shown that they all predict a similar relation between constant stress and constant stress rate failure strength. It is also demonstrated that the methodology proposed by Miyano et al., based on linear damage accumulation law (LCD), produces similar results.Experimental cases published in literature are used to illustrate the theoretical approaches. Finally it is suggested that Monkman–Grant classical equation can be used as a failure criterion for constant strain (or stress) rates. The extrapolation for lower strain rates would permit the long-term strength prediction, based on viscoelastic constitutive law. At last creep strength could be obtained from strength curves by using Miyano et al. methodology.