The composites with higher fiber volume fraction and longer fiber length are more sensitive to strain rate. Both elastic modulus and flow stress at any given strain increased with strain rate. Experimental results show that the compressive behavior of MGf/PU composites is nonlinear and strain-rate-dependent. The compression tests at different strain rates (0.001, 0.01, 0.1, 1, 20 s−1) and dynamic mechanical properties over the temperature range from −30 to 100 ☌ at 1 Hz were performed. It was found from the FTIR studies that the incorporation of milled glass fiber into polyurea leads to more phase mixing and decreases the hydrogen bonding of the polyurea matrix, while having a negligible effect on the H-bond strength. Moreover, it seems that the composites with longer fiber exhibit better interfacial bonding. The SEM investigations revealed a uniform distribution and arbitrary orientation of milled glass fiber in the polyurea matrix. The morphological attributes were characterized with scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The volume fraction and length of the milled glass fiber were varied to study their effects on the morphological and mechanical properties of the MGf/PU composites. 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.Ĭomposites of polyurea (PU) reinforced with milled glass fiber (MGf) were fabricated. 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. 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. 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. 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. The energy absorption of T26 polyurea is realized through the interaction between the hard and soft segments. It is significantly influenced by the ambient temperature and loading frequency. The results show that the glass transition region of T26 polyurea is −40 ☌ to 10 ☌, which is a large temperature range, and the microphase separation of T26 polyurea is low. The chemical structure changes of the blast-face coating before and after the explosion were compared by Fourier transform infrared spectroscopy (FTIR).
Scanning electron microscopy (SEM) was employed to analyze the microscopic fracture morphology of the typical areas of the coating after the explosion. Protective performance of T26 polyurea on RC slab was examined with a 10 kg TNT contact explosion test. The response and energy absorption capacity of the material towards different frequency loads were investigated by dynamic mechanical analysis (DMA). 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. 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.
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