A time based model for the dielectric ageing of Fibre Reinforced Polymers (FRP) and its verification in a numerical simulation

A model for the water influenced dielectric ageing and the electrical breakdown behaviour of FRP is given, using chemical mechanisms and numerical calculations to explain the measured increase of the loss tangent, the dielectric constant and the fibre orientation of the breakdown channel along the fibres. For insulation applications the most important property of a FRP composite is the electrical strength at the interphase between glass fibre and resin bulk. The degradation of this parameter can be observed when worsening the mechanical interphase adhesion during watering. From the electrical as well as from the dielectrical point of view, the FRP properties are mainly interphase affected: the surface conductivity of glass on the one hand and the detachment process, causing a electrolyte filled crack, on the other hand are the most important features.