The Impact Resistance Study Of Polyurea Composite Structures

Polyurea has a wide application prospect in the protective engineering fields becauseof its excellent mechanical performance. In this paper, the shock resistance property of thecomposite structure was investigated from the energy dissipation mechanism, failuremechanism and speed effect, and through experiments and numerical calculation methods.The polyurea composite structure was fired from the velocity300m/s to450m/s, withsteel-tipped7.62calibre projectiles. The composite structure has three types: uncoatedaluminium plates, sandwich structure and the coating structure, and it composted of LY12aluminium plates (the total thicknesses are4mm) and SPUA-502polyurea (the thicknessesare6mm) and its total thicknesses are10mm. The input and output velocities weremeasured using two laser velocity screens. The effectiveness of the polyurea coating anddifferent structure in terms of reduction of the residual velocity, damage mechanism, kineticenergy absorption of the plates are presented and discussed. By comparing the test results,the reduction of residual velocity due to the presence of polyurea coating has beenquantified, the coating structure is strongest and with the increase of the impact velocity,the velocity reduction increase. Dissipation of kinetic energy of the coating structure is1.10times the uncoated aluminum structure and1.36times the sandwich structure. Polyureashows higher energy absorption capacity per unit areal density than aluminium, dissipationof kinetic energy of the polyurea coating layers is1.29times the aluminium and2.73timesthe polyurea core layers. From the cross-section, the uncoated aluminium plate showsconical propagation, once this pattern reaches the polyurea coating, a reverse formation ofthe conical crater occurs as the diameter decreases and found a small amount of aluminumscraps in PU layers. This indicates the feasibility of the polyurea to act as a protectiveshield against flying particles and fragments.Combined with experiments results, a series of numerical experiments were carried outusing LS-DYNA program, which verified the reliability of the material model and failurecriteria at first. Subsequently we extend study the new composite structure-layeredcomposite structure (the total thicknesses are10mm). In this structure, polyurea layer bothas a sandwich and as a coating, and the thickness change. We found that the layered composite structure has better performance of shock resistance, and the residual velocitiessmaller. And at all of the numerical experiments, when polyurea layers as the structurescoating, the projectile velocity has a small up before it penetration the structures. And at last,the schematic representation given in further elaborates the ductile crater formation throughthe thickness of each layer for all the configurations structure.