High-hardness polyurea coated steel plates subjected to combined loadings of shock wave and fragments

Abstract

To investigate the effect of polyurea on the protective performance of a steel target plate under the combination of shock wave and fragments, the failure characteristics, damage process and micro mechanism of the polyurea coated steel plates with different coating methods under the combination of explosion shock waves and fragments were analyzed through experiments and numerical simulations. The results showed that single-sided coatings aggravated the damage of target plate when the coating thickness was 2 mm. While the polyurea thickness greater than 4 mm could significantly reduce the damage degree of the steel plate. When the polyurea was coated on the double sides, it would aggravate the damage, no matter how thick the polyurea was. Through microscopic research, it was found that the front coated polyurea was severely ablated by detonation products, which greatly reduce its energy absorption efficiency. The polyurea coated on the back underwent tensile fracture under the influence of tensile stress wave. The breaking of intramolecular hydrogen bond of polyurea was the key to the energy absorption of polyurea.

Polyurea for Blast and Impact Protection: A Review

“…The polyurea spray construction process is one of the key attributes of polyurea that makes it widely used in various fields. Due to the fast curing characteristics of sprayed polyurea, the coating section shows a loose and porous cheese-like structural feature after the reaction film formation, which is favorable for absorbing energy under high-speed loads [36]. Controlling the reasonable matching of the viscosity of amines and isocyanates through the design of the polyurea formulation is an important part of optimizing the performance of polyurea spraying.…”

“…Lyu et al [13] observed by thermogravimetric experiments that the thermal decomposition rate of polyurea reached the maximum at a temperature of 386 • C. At a temperature of 700 • C, the polyurea decomposed into carbon residue and lost its protective properties [13]. By comparing the FTIR spectra of polyurea before and after the explosion, Zhang et al [36] found that the area of the carbonyl stretching region and imino stretching region was decreased. It was shown from the practical explosion data that the hydrogen bonds in polyurea were broken, and the microphase separation was also damaged after subjecting the polyurea to the explosion load.…”

“…The polyurea coating on the backside dissipates energy by tensile deformation and reduces the impact of shock waves on the metal structure, inhibiting structural deformation. On this basis, Zhang et al [36] revealed that, under the combined effect of blast shock waves and fragmentation, the damage to the steel plate is reduced despite the fracture damage of the high-hardness polyurea on the backside. Chen [32] and Li et al [33] found that full-area spraying on the backside offers far better protection than partial spraying because of the confined polyurea boundaries, which can absorb energy through tensile deformation and the peeling of the coating.…”

“…By analyzing the microscopic morphology of the blast surface (Figure 12b), Wu et al [16] concluded that high temperature resistance and flame retardancy are essential properties of polyurea against blast loads. It was concluded by Zhang et al [36] that the severe ablation of the blast surface by the detonation products substantially reduce the energy absorption efficiency of the coating. Comparing the energy absorption efficiency of the coating on the blast side and the back blast side, it is undeniable that the energy absorption efficiency of the coating on the blast side is lower.…”

“…Rijensky et al [119] revealed through simulations that the strength characteristics of the primer used prior to this coating should be considered in blast resistance protection. Premature cracking of the polyurea after the failure of adhesion to the substrate limits the effect of the polyurea on energy absorption [36].…”