A computational analysis of the utility of chemical reactions within protective structures in mitigating shockwave-impact effects

Abstract

Purpose The purpose of this paper is to introduce and analyze a new blast-wave impact-mitigation concept using advanced computational methods and tools. The concept involves the use of a protective structure consisting of bimolecular reactants displaying a number of critical characteristics, including: a high level of thermodynamic stability under ambient conditions (to ensure a long shelf-life of the protective structure); the capability to undergo fast/large-yield chemical reactions under blast-impact induced shock-loading conditions; large negative activation and reaction volumes to provide effective attenuation of the pressure-dominated shockwave stress field through the volumetric-energy storing effects; and a large activation energy for efficient energy dissipation. The case of a particular bimolecular chemical reaction involving polyvinyl pyridine and cyclohexyl chloride as reactants and polyvinyl pyridinium ionic salt as the reaction product is analyzed. Design/methodology/approach Direct simulations of single planar shockwave propagations through the reactive mixture are carried out, and the structure of the shock front examined, as a function of the occurrence of the chemical reaction. To properly capture the shockwave-induced initiation of the chemical reactions during an impact event, all the calculations carried out in the present work involved the use of all-atom molecular-level equilibrium and non-equilibrium reactive molecular-dynamics simulations. In other words, atomic bonding is not pre-assigned, but is rather determined dynamically and adaptively using the concepts of the bond order and atomic valence. Findings The results obtained clearly reveal that when the chemical reactions are allowed to take place at the shock front and in the shockwave, the resulting shock front undergoes a considerable level of dispersion. Consequently, the (conserved) linear momentum is transferred (during the interaction of the protective-structure borne shockwaves with the protected structure) to the protected structure over a longer time period, while the peak loading experienced by the protected structure is substantially reduced. Originality/value To the authors’ knowledge, the present work is the first attempt to simulate shock-induced chemical reactions at the molecular level, for purposes of blast-mitigation.

Fluent Numerical Study of Lifting Resistance and Wave Impact Height of a Cross‐Sea Bridge Based on Cloud Computing

“…Considering the various loads in the design, the same modeling method was applied to the finite element analysis of the real bridge. After analysis, he finally confirmed that this new type of bridge meets the specifications for strength, stiffness, and crack resistance [8]. Chen believes that the construction of transportation infrastructure has a profound impact on the coordinated development of the regional economy and urban agglomerations.…”

The shockwave dispersion/attenuation potential of a protective structure made of a chemically reactive mixture

“…The specific chemical reaction investigated by Grujicic, Snipes and Ramaswami (2016) involved polyvinyl pyridine, (-CH 2 -CH(C 5 H 4 N)-) n , and cyclohexyl halides, (C 6 H 7 R 2 R′ 2 X; X ¼ Cl, Br, I; R,R′ are functional groups), as reactants, and ionic pyridinium salt (-CH 2 -CH (C 5 H 4 N + -C 6 H 7 R 2 R′ 2 )-) n •nXas product. Molecular configurations of the reactants and the products of this reaction are depicted in Figure 1.…”

“…reactions wherein the transition state has a cyclic geometry and the reaction progresses in a concerted fashion) may occur (Davis et al, 2009). In our prior work (Grujicic, Snipes and Ramaswami, 2016), the following two families of chemical reactions have been identified as potentially possessing the four characteristics described above: ionic-particle-formation reactions (described in greater detail below); and Diels-Alder reactions (organic reactions between a 1, 3-conjugated four-carbon linear chain (like 1, 3-butadiene) and a substituted two-carbon alkene (i.e. ethene) to form a substituted cyclohexene).…”

“…ethene) to form a substituted cyclohexene). Only the first type of chemical reactions was investigated by Grujicic, Snipes and Ramaswami (2016). Reactions of this type are often classified as: bimolecular, i.e.…”

“…It is generally established that bimolecular reactions are more versatile (an advantage), but their reaction rate is more difficult to control (a potential drawback), than unimolecular reactions. Since the primary concern of the work presented by Grujicic, Snipes and Ramaswami (2016) was sufficient extent of the shock-induced chemical reactions, only (one case of) the bimolecular ionic-particle-formation reaction was investigated.…”