This study describes a simple, practical, inexpensive, improved, and efficient novel method for obtaining polyurea-polyurethane-multiwall carbon nanotubes (MWCNTs) nanocomposites with enhanced mechanical properties, and their experimental testing in a dynamic regime. SEM and micro-CT investigations validated the homogeneity of the nanocomposite films and uniform dispersion of the nanofiller inside the polymeric matrix. The experimental measurements (TGA, DSC, DMA, and tensile tests) revealed improved thermal and mechanical properties of these new materials. To demonstrate that these nanocomposites are suitable for ballistic protection, impact tests were performed on aluminum plates coated with the polyurea-polyurethane MWCNTs nanocomposites, using a Hopkinson bar set-up. The experimental testing in the dynamic regime of the polyurea- polyurethane-coated aluminum plates confirmed that the nanocomposite layers allow the metal plate to maintain its integrity at a maximum force value that is almost 200% higher than for the uncoated metallic specimens.

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Abstract. This study refers to an experimental and numerical evaluation of a polyurea coating layer influence on the dynamic behaviour of OL50 specimens. Mechanical quasi-static and dynamic tensile tests were performed in axial loading conditions, for 2 mm steel plate specimens. Several metallic specimens have been previously coated with 1.5 mm and 3 mm respectively thickness polyurea layer and tested in traction. The findings results indicate that the presence of polyurea changes the loading pattern of metallic material in the necking area. In terms of polyurea coated metal specimens fracture, there was clearly observed a change of fracture limit. One possible explanation of this phenomenon is the modification of triaxiality state in the necking zone, fact proven by the numerical simulations. Test results indicate that the presence of polyurea layer delays the necking onset phenomenon which precedes the OL50 metallic specimen fracture.

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This study addresses some aspects regarding water jet propulsion during high explosives detonation. A number of theoretical and experimental studies have shown that using Gurney equation and the relationships derived, one can provide fair results regarding initial velocity of metallic fragments for explosively‐driven metal casings. However, an investigation on Gurney equations utilization for the prediction of water velocity has not been performed yet. By carrying out simple experimental tests and numerical simulations, water has been investigated in terms of total mass average velocity and tip velocity. Based on the available data, the findings indicate that Gurney equations overestimate the water mass average velocity. For water tip velocity evaluation, further studies should be made.