MECHANICAL MODELING OF BLISTERS ON COATED LAMINATES .1. THEORETICAL ASPECTS

Fibreglass reinforced polyester laminates with gelcoat are subject to blistering when immersed in sea water or in fresh water, leading to a delamination of these materials. Several accelerated ageing tests were performed on these materials to study this degradation process in both sea and distilled waters. This paper presents mechanical models in order to evaluate the internal pressure of the blisters and the lifetime of the materials. It is shown that existing thermodynamic models are not sufficient to estimate the dependence of the pressure and stresses on the age, and a more appropriate model, from the theory of plates, is described. The model considers a blister to be a circular membrane clamped on its circumference and uniformly loaded. The edges of the blister are not perfectly clamped however, so the theory of plates with elastic clamping is the most representative for modelling blisters.