Study On Protective Effect Of Polyurea Coated Steel Composite Structure Under Intense Dynamic Loading

As an emerging protective material,polyurea is widely used in armor structures such as steel plates and composite materials to improve the protective performance of composite structures.Studying the protective effect of polyurea coating and analyzing the failure mechanism can provide theoretical support for the design of antiknock and anti-ballistic composite structures.Based on the basic mechanical properties of polyurea materials,this paper studies the anti-penetrating and antiknock effect of polyurea coated steel composite structures,the completed works and main conclusions are as follows:(1)For polyurea materials under strain rate 0.001/s~4000/s,the mechanical behaviors,the stress-strain curves at various strain rates,the strain rate effect and the strain hardening rate are obtained through quasi-static,dynamic tension and compression tests.the strain hardening rate of polyurea material increases as true strain increases that is found in the quasi-static test;while in the dynamic test,the strain hardening rate decreases with the increase of true strain.The damage and failure law of the inner and outer surfaces of the polyurea samples under tensile and compressive one-dimensional stress wave loading was studied through the microscopic observation of the test sample was carried out by optical microscope and SEM.It founds that the crack tear polyurea structure,this phenomenon are thought to be the reason for material failure.(2)Based on the ballistic impact experiments results of 35 GrMnSiA projectiles to composite structures: bare steel plate,front coating-coated steel plate and back coating coated steel plate,the high-speed penetration resistance of the thress composite structures was studied.The effects of the polyurea coating and integral composite structure on ballistic limit and energy absorption increment under the condition of unit areal density are studied.Based on the back coating coated steel plate,regardless of the polyurea coating or the integral composite structure,the increment of the two indexes is higher than that of the front coating coated composite structure.Moreover,the failure mechanisms of the peeling specimens at the break of polyurea coating were analyzed by scanning electron microscope,it was found that the polyurea material exhibits a certain brittleness under high strain rate loading,and exhibits obvious shear and tensile failure modes.(3)Based on the static explosion load loading experiment,the antiknock effect of polyurea coated steel composite structures such as bare steel plate,front coating-coated steel plate and back coating coated steel plate was obtained.On the one hand,the effect of polyurea coating thickness on the antiknock effect of polyurea coated steel composite structure was studied under the condition of equal surface density.The analysis found that the thickness of the polyurea coating has an inhibitory effect on the improving of the antiknock performance of composite structure.On the other hand,under the condition of polyurea coating with equal thickness,the effect of different spraying methods on the antiknock effect of the composite structure,It found that the back polyurea coating inhibits the deformation and damage of the steel plate by virtue of its excellent elongation and other characteristics,thereby improving the explosion resistance of the composite structure.Based on the microscopic analysis of the shed polyurea coating by scanning electron microscope,it is found that the coating under the explosive load loading has obvious shear and tensile failure.