Strengthening and converse strengthening effects of polyurea layer on polyurea–steel composite structure subjected to combined actions of blast and fragments

Abstract

Coating polyurea can significantly enhance the blast and impact resistance of thin-walled metal structures. However, most current research focuses only on the condition of single damage factor, such as blast or penetration loading. In this paper, the protective performance of polyurea-coated steel plates under the combined actions of blast and high-speed fragments was studied by means of field tests. Test results showed that under the combined actions of blast and high-speed fragments, when the coating thickness was within a certain range, polyurea had a converse strengthening effect on the protective performance of steel plate no matter which configuration was adopted. Only when the coating thickness exceeded a certain value did polyurea play a strengthening role. In other words, an obvious inflection point effect occurred in the influence of polyurea thickness on the protective performance of steel plate. These phenomena seem to be related to the characteristics of combined actions, which was different from that of single load. On the basis of tests, the strengthening and converse strengthening effects of polyurea layer was explained through microscopic analysis, numerical calculation and stress wave propagation theory. The significance of this research was to reexamine the practical application method of polyurea in improving the protective performance of metal thin-walled structures under specific circumstances to provide technical guidance for engineering application.