The work presented in this thesis document is concerned with the investigation of the dynamic behaviour of Fibre Reinforce Plastic (FRP) laminated and sandwich plates composed of a PolyVinylChloride (PVC) foam core material. An extensive review, covering existing modelling techniques for FRP composite plates and for viscoelastic materials as well as published viscoelastic material data, has highlighted many areas of limitations. A comprehensive theoretical study was therefore carried out in order to develop new analytical models. It has been demonstrated that Reddy's refined HSDT appears to be the most versatile and accurate modelling method for FRP laminated and FRP sandwich plates for which dynamic responses need to be predicted. Since FRP laminated and FRP sandwich plates are made of, amongst other things, PVC foam material and/or resin system which exhibit viscoelastic damping, the method has been enhanced to offer the possibility to predict the forced response and the steady state response of such panels, while taking into account their material viscoelastic properties. The new models have been developed by combining the HSDT with viscoelastic material modelling tools namely the elastic viscoelastic correspondence principal or the GHM mathematical method offering the feasibility to carry out either steady state of transient analysis. In parallel to the development of novel analytical models, experimental testing has been carried out in order to gain knowledge and data on the dynamic properties and behaviour of virgin and damaged PVC foam materials. Finally results from the experimental and the theoretical aspects of the research have been combined and the dynamic analysis of specific FRP sandwich plates has been realised. From this research work, a better understanding of the dynamic behaviour of undamaged and damaged FRP composite panels with designated viscoelastic material properties has been acquired.