The main emphasis of this paper is to identify long-term effects such as creep and creep-fatigue interaction for a typical sandwich structure incorporating FRP (fibre-reinforced plastic) faces and a PVC (polyvinyl chloride) foam core. For the creep modelling a Bürger model and a power law model are investigated and compared with experimental results. Fatigue results pertaining to a cyclic trapezoidal waveform are presented in the context of the creep-fatigue interaction. A cyclic creep model is developed in order to investigate the effect of cyclic creep deformation on a response containing elements of fatigue and creep. A simple linear damage rule separating the creep and fatigue components for the chosen cyclic waveform is used in order to quantify the relative influence of both components on the lifetime of the structure. Finally conclusions are drawn regarding the aptness of the chosen creep and creep-fatigue interaction models.