The effect of frequency on the fatigue performance of filament-wound pipes under biaxial loading: Experimental results and damage model

The fatigue performance of [+55, -55] laminated composite pipes has been investigated. In the first part of this paper, the experimental results obtained under biaxial lending are described. The effect of frequency on damage and lifetime is analysed. The experimental results exhibit an increase in the life with frequency. As regards damage, it can be shown that the rate of damage per cycle is also dependent on the frequency. This phenomenon is mainly due to the creep-fatigue interaction. In the second part of the paper, a model is proposed which is capable of describing the frequency effect. The model uses a damage variable previously introduced in another paper to describe the instantaneous phenomena. The kinetics of damage are obtained by using a set of internal variables which are defined here. (C) 1997 Elsevier Science Limited.