Alexandre Perrot

Ultra-high performance fiber-reinforced concrete (UHPFRC) can be used to build lightweight bulletproof structures because even its thin layer can prevent projectile perforation. UHPFRC is significantly less expensive than other armor materials such as steel, Kevlar, nylon, or ceramic. It has good volume stability and very low porosity, which makes it highly durable and provides sufficient resistance to freeze-thaw cycles. However, when a projectile hits a thin UHPFRC structure, the fragments can break off. The fragments can injure people or damage property in the vicinity of the structure. To address this problem, we have developed a new generation of sandwich structures consisting of a UHPFRC core, a fiber-reinforced epoxy composite, and an elastomeric coating. UHPFRC and composite provide penetration resistance. Composite and elastomer reduce fragmentation of UHPFRC. By properly designing these three materials, their thickness, and their position in the sandwich structure, lightweight and affordable bulletproof panels can be produced. This contribution presents such a structure and subjects it to ballistic testing according to European and American standards. It is shown that the additional layers eliminate the formation of rear fragments after projectile impact and reduce the panel weight by 13% compared to the panel made entirely of UHPFRC. Due to their unique shape, the panels can be combined to form a mobile and modular protective barrier. The barrier can take the form of a freestanding wall with various opening angles, or an outpost with a square or hexagonal base. It can be moved and assembled quickly by just two people.

Dicyclopentadiene (DCPD) modified unsaturated polyester resins (UPRs) are mostly used for hulls, decks, and bathroom facilities. Main advantages of these polymers over orthophthalic or isophthalic polyesters are their relatively low shrinking, reduced styrene emission, lower cost, and fast curing in thin layers. On the other hand, once cured, these materials are more brittle and have lower glass transition temperatures and lower chemical resistance due to their different chemical constitutions. DCPD UPRs with standard grades are usually produced with high-quality DCPD (over a 85% purity) using the so-called “water process”, a synthesis consisting of two reaction steps. An adduct of maleic anhydride with DCPD is firstly formed with water, and then, it reacts with the other esterification monomers such as acids and glycols. DCPD raw materials used in this study were prepared by a unique distillation process developed by ORLEN Unipetrol and University of Chemistry and Technology, Prague. This technology allows producing a wide spectrum of DCPD quality by adjusting the content of another norbornene dimer: methyl dicyclopentadiene (MeDCPD). The influence of MeDCPD on unsaturated polyester properties was examined throughout this study. It has been discovered that in low concentrations, MeDCPD had a slight influence on flexural mechanical properties whereas its concentrations up to 65% led to a softer and brittle material. Nevertheless, by adjusting the unsaturation degree, it has been shown that MeDCPD may be successfully implanted in UPR formulation.