Relationship between epoxy resin properties and weepage of glass-reinforced filament-wound pipes

Abstract

This study aims to understand the relationship between mechanical properties of a resin and weepage (loss of water tightness) of glass-reinforced filament-wound pipes. A three-stage study has been carried out, from epoxy resin chemistry to mechanical behaviour of composite pipes under pressure. Four resin formulations were selected by accounting for their different mechanical characteristics in tension. The study of unidirectional composite plaques showed that fracture in tension transversally to the fibre direction essentially comes from the failure of the fibre/matrix interface. The failure strain of these plaques is higher when the strain of the resin at failure of the fibre/matrix interface is higher. Biaxial pressure tests on ± 55°-filament-wound pipes revealed that weepage is due to the transversal failure of unidirectional layers of the pipe wall. Moreover, a very simple weepage criterion was proposed: weepage appears for a pressure directly proportional to the failure strain of unidirectional composite plaques in tension transversally to the fibre direction. The proportionality constant depends on the pipe geometry.