Study of Blast Mitigation Performance and Fracture Mechanism of Polyurea under Contact Explosion

Abstract

In order to further study the blast mitigation performance of polyurea and to investigate the protection mechanism and damage characteristics of polyurea-protected structures under contact explosion loads, based on earlier work, this paper investigated the response and energy absorption performance of polyurea under various frequency loads. Qtech T26 blast mitigation polyurea (T26 polyurea) was adopted to protect the reinforced concrete (RC) slab and damage analysis of the post-explosion specimens was carried out at micro and macro levels. The response and energy absorption capacity of the material towards different frequency loads were investigated by dynamic mechanical analysis (DMA). Protective performance of T26 polyurea on RC slab was examined with a 10 kg TNT contact explosion test. Scanning electron microscopy (SEM) was employed to analyze the microscopic fracture morphology of the typical areas of the coating after the explosion. The chemical structure changes of the blast-face coating before and after the explosion were compared by Fourier transform infrared spectroscopy (FTIR). The results show that the glass transition region of T26 polyurea is −40 °C to 10 °C, which is a large temperature range, and the microphase separation of T26 polyurea is low. It is significantly influenced by the ambient temperature and loading frequency. The energy absorption of T26 polyurea is realized through the interaction between the hard and soft segments. When the frequency is between 102 Hz and 106 Hz, the loss factor of T26 polyurea is between 0.20 and 0.31, which exhibits a good energy dissipation performance. In the contact explosion of 10 kg TNT, the fragmentation rate of the coated specimen decreased significantly compared with that of the unprotected specimen, realizing the zero fragmentation protection effect on the back-blast face. The maximum deformation area and the main energy absorption area of T26 polyurea under contact explosion is the ring area outside the longitudinal deformation area. The chemical structure of T26 polyurea changed significantly after the explosion; typically the N-H bonds, etc., were broken and the percentage of hydrogen bonding was reduced. T26 polyurea has realized the protection effect of zero fragmentation of large-equivalent contact explosion, which has a high application value for blast mitigation and blast-fragmentation prevention in actual engineering.

Recent Developments in Polyurea Research for Enhanced Impact Penetration Resistance and Blast Mitigation

“…Sun et al [40] observed an increased absorption of localized impact energy at approximately 115 • C, which corresponds to the transition temperature from the glassy to the rubbery state when subjected to high-speed dynamic loading. Notably, materials that exhibit a wider temperature range in the glass transition zone and lower microphase segregation demonstrate superior flexibility and energy absorption under high strain rate loading conditions [41,42].…”

“…Upon impact, the ordered arrangement of the hard segments is disrupted, resulting in a reduction in the number of hydrogen bonds. The dissociation of hydrogen bonds leads to a substantial increment in the potential [41,46]. Additionally, the soft phase stores a greater amount of strain energy compared to the hard phase under impact.…”

“…High-performance polymer materials with exceptional strength, toughness and durability are well-suited for this purpose. The fracture mechanism of these materials, when subjected to contact explosions, encompasses various factors, including the high-temperature mechanical property destruction mechanism, hightemperature impact load coupling fracture mechanism, high-speed load brittle fracture mechanism and tensile fracture mechanism [41,42]. These mechanisms collectively contribute to the material's behavior under extreme conditions.…”

“…Additionally, composite sandwich structures can be created to effectively handle damage across various situations [70,71]. Studies and simulations have demonstrated that plain reinforced concrete (NRC) protected with polyurea experiences reduced damage and residual displacement, showcasing its efficacy in enhancing blast resistance in NRC panels [41,42,[72][73][74][75][76][77]. Autoclaved aerated concrete (AAC) panels, known for their lightweight nature, exceptional thermal insulation and energy absorption properties, are ideal materials for protecting structures.…”

“…With its excellent adhesion and ductility properties, polyurea coating proves to be an effective solution for reinforcing existing blast-resistant structures. W. Huang et al [41] studied the protective performance of T26 polyurea on reinforced concrete (RC) slabs using a 10 kg trinitrotoluene (TNT) contact explosion test. The T26 polyurea coating was applied using PHX-40 proportioner (PMC Global, Inc., Branford, CT, USA), with the reaction volume ratio of component A to component B set at 1:1.…”