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

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.