A computational analysis of the utility of chemical reactions within protective structures in mitigating shockwave-impact effects. Issue 3 (10th October 2016)

• Record Type: Journal Article
• Authors: Grujicic, Mica; Snipes, Jennifer; Ramaswami, S.
• Is Part Of: Multidiscipline modeling in materials and structures. Volume 12:Issue 3(2016)
• Page Start: 438
• Page End: 472
• Publication Date: 2016-10-10
• Subjects: Blast-wave impact-mitigation -- Shock-induced chemical reactions -- Protective structure -- Bimolecular reactants -- Polyvinyl pyridine -- Cyclohexyl chloride; Materials -- Mathematical models -- Periodicals; Engineering -- Mathematical models -- Periodicals; 620.11015118
• DOI: 10.1108/MMMS-04-2015-0019
• Languages: English
• ISSNs: 1573-6105

Abstract

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.