Tailoring Dynamic Bonding in High Strain Rate Elastomeric Polymers for Blast Protection
Abstract
Elastomers are typically thought of as weak and compliant relative to traditional structural materials, but in fact can show impressive toughness, particularly when employed as a coating. Polymeric explosion resistant coatings can protect structural materials and critically, personnel near the structures from blast and ballistics. While these explosion resistant coatings have been inuse for over 15 years, their design is still largely trial and error. Polyurea is the most prominent high strain rate elastomeric polymer for blast protection applications. At high strain rates and pressures, the strength of polyurea rivals that of high strength steel, ceramics, and composites, but with much lower density. Although simulations have been used to accurately predict how polyureawill protect a structure, they have been used in only a very limited and post hoc manner to improve the polymer itself.Here, we propose a multiscale modeling approach to evaluate the role of dynamic bonding within existing state-of-the-art high strain rate elastomeric polymers and further to synthesize and evaluate newly proposed materials for which the dynamic bonding is stronger. For the purposes of this proposal we will refer to the version of the polymers with stronger dynamic bonding as metallo-polyurea since the dynamic bonding will be achieved through ionic bonding of thepolymer backbone with divalent metal cations. The proposed work will be accomplished through three parallel and complimentary tasks: (1) Utilize bond kinetics simulations and all atom molecular dynamics (MD) simulations to determine the constitutive behavior of each phase of the polymer and how material evolves from one phase to the other; (2) Quantify the overall responseof the polymers to monotonic and cyclic loadings with continuum simulations that explicitly represent the phase-segregated morphology with constitutive models of each phase. The realistic morphology RVEs will be informed by coarse grained MD simulations; (3) Synthesize and experimentally characterize the morphology and mechanical properties of polyurea and metallopolyurea.Morphology will be measured in-situ with x-ray scattering during quasi-static tension and hydrostatic pressure loading at the Cornell High Energy Synchrotron Source. Density Functional Theory (DFT) simulations will also be conducted to obtain the force-modified bond breaking energetics. This ambitious technical approach utilizes my broad expertise in polymer mechanics, encompassing synthesis, experiments, MD simulations, FEA simulations, and constitutive modeling; and my focused expertise in manipulating polymer properties withpurposefully weak bonds. This work will lead to a new way to tailor polymer coatings for blast and ballistics protection of sea platforms, vehicles, and people. Such protection is particularly important for defense against terrorism and irregular warfare. Polymer coatings are a good approach to improving the toughness of these structures because they are lightweight, low cost, and critically, can be used to retrofit existing structures. The customization of the dynamic bonding will enable stronger, tougher polymers that are capable of surviving and dissipating the blast energy, and can suppress localization of substrate yielding. Further, we will create new fundamental knowledgefor designing polymers with non-covalent bonds not just targeting use as coatings, but also in composites and as structural materials. By integrating the incredibly flexible metal coordination bond motif into block copolymers and understanding the fundamentals of the force-modified dynamics, we will be able to achieve polymers that span from viscous fluids to tough glasses.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 24, 2019
- Source ID
- N000141912099
Entities
People
- Meredith N Silberstein
Organizations
- Cornell University
- Office of Naval Research
- United States Navy