Study On Mechanical Properties Of Polyuria-coated Concrete Under Impact Load

Nowadays,while facing static loads,concrete structures are also vulnerable to explosion and impact loads,such as earthquakes and explosions.At the same time,buildings are often damaged by dynamic loads.Although these loads act for a short time,they have a significant impact on the building,and this impact can easily cause sudden damage to the building,which can lead to casualties and property losses.Therefore,it is necessary to strengthen the protection of concrete structures such as buildings,enhance the explosion and impact resistance of concrete structures,and reduce sudden damage to buildings.The polyurea material has excellent wear resistance,impact resistance,and explosion resistance,which is an excellent protective coating.At the same time,the polyurea material also has convenient construction,strong adhesion to base materials such as concrete,and can ensure long-term coating use without peeling.Polyurea can effectively wrap structural debris to prevent secondary injury to personnel in the event of disasters.Due to the limitations of experimental conditions,it is difficult to accurately reflect the mechanical response of some complex working conditions.Therefore,this article uses the finite element software LS-DYNA to establish a polyurea coated concrete SHPB model based on the SHPB test conditions of concrete and polyurea coated concrete in reference literature,and on the basis of dynamic and static compression tests of polyurea.After verifying the effectiveness of the model,Within the impact speed range of 5-20m/s of the impact rod,the dynamic compressive mechanical properties of polyurea coated concrete composites were studied,including the influence of different polyurea coating thicknesses,the influence of polyurea coating positions,and the influence of polyurea coating on the strength of concrete substrates.Specifically,the main conclusions drawn in this article are as follows:(1)Under the same speed impact of the impact rod,as the coating thickness increases,the energy consumption coefficient of the composite gradually increases to a certain peak and then decreases.When polyurea is coated on the concrete impact surface and the coating thickness increases to 3mm,the energy consumption coefficient reaches its peak;When polyurea is coated on the concrete rebound surface and the coating thickness increases to 4mm,the energy consumption coefficient reaches its peak.(2)Under different velocities of impact,the incident energy of composite components with the same coating thickness significantly increases with the increase of impact velocity.At the same time,the energy consumption coefficient first increases and then decreases with the increase of incident energy within a certain range,and reaches the peak of the energy consumption coefficient around 0.48.(3)As the thickness of the coating increases,the cracks and fragments in the concrete gradually decrease on both sides,the rebound surface,and the rebound surface of polyurea coated concrete.Moreover,the rebound surface of the coated concrete is better than that of the coated concrete.However,when the thickness of the coating increases to about 5mm,this pattern is no longer obvious.(4)When the polyurea coating is impacted at different positions at the same speed,the peak stress of the composite gradually decreases as the thickness of the coated concrete increases,but the time required for the composite to reach the peak stress gradually increases.Polyurea coating can improve the brittleness of concrete,effectively slow down the time of concrete failure,and increase the deformation of the composite component to failure during dynamic compression.(5)As the strength of the concrete increases,the percentage increase in the time it takes for the polyurea coated concrete to reach the peak stress on the rebound and rebound surfaces gradually decreases.When impacted at the same speed,the energy dissipation effect of polyurea coated concrete composite is better than that of concrete.When the dynamic compressive peak stress of polyurea is not less than the compressive strength of the concrete substrate,the energy absorption of the composite is the best.