Investigation of a fast mechanical self-repair mechanism for inflatable structures

The self-repair mechanism of flexible cellular as well as dense polyurethane coatings applied on the internal side of a commercially available membrane for inflatable structures was investigated. In a dedicated test setup the coated membrane was punctured with a spike of 2.5 mm in diameter and the flow of the leaking air was measured. Parameters such as the coating thickness and coating weight as well as the mechanical properties and microstructure were varied and their influence on the repair efficiency of the coatings analysed. The mechanism underlying the self-repair effect was identified and found to be the result of compressive strains in the coating layer, mostly induced by the curvature of inflated membranes. The strain situation in the coating layer is for a given curvature most exclusively dependent on the thickness of the applied coatings. With respect to a minimum in coating weight, flexible closed cell foam coatings yield the most promising repair efficiencies (>0.99).