Bulletin of the American Physical Society
19th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 60, Number 8
Sunday–Friday, June 14–19, 2015; Tampa, Florida
Session V3: Soft Matter II: Polymers & Bio |
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Chair: Clive Siviour, University of Oxford, Kyle Ramos, Los Alamos National Laboratory Room: Grand G |
Thursday, June 18, 2015 3:45PM - 4:00PM |
V3.00001: Shockwave Absorption using Network-forming Ionic glass Jaejun Lee, Ke Yang, Jeffrey Moore, Nancy Sottos Network-forming ionic glasses composed of di-ammonium cations and citrate anions exhibit significant potential for dissipation of shock wave energy. The long alkyl side chains in the di-ammonium cation form a soft matrix, while the negatively charged heads of anions segregate into hard nanophase domains. Similar to polyurea, which has microphase separation of soft and hard domains, we hypothesize that shock wave dissipation of the ionic glass occurs by bond breaking in the hard domains and/or pressure-induced phase transition. By employing size-tunable alkyl side chains in the cations, we examine the effect of the relative soft domain size on energy dissipation. A series of thin film (ca. 50 $\mu$m) ionic glass specimens are subjected to laser-induced compressive stress waves and the transmitted response measured interferometrically. Structural changes of the ionic glass due to shock wave impact are characterized by x-ray diffraction. When compared directly to polyurea films of identical thickness and geometry, the ionic glass showed superior shock-wave mitigating performance. [Preview Abstract] |
Thursday, June 18, 2015 4:00PM - 4:15PM |
V3.00002: Constitutive Modeling of the Dynamic-Tensile-Extrusion Test of PTFE Anatoly Resnyansky, Eric Brown, Carl Trujillo, George Gray Use of polymers in the defence, aerospace and industrial application at extreme conditions makes prediction of behaviour of these materials very important. Crucial to this is knowledge of the physical damage response in association with the phase transformations during the loading and the ability to predict this via multi-phase simulation taking the thermodynamical non-equilibrium and strain rate sensitivity into account. The current work analyses Dynamic-Tensile-Extrusion (DTE) experiments on polytetrafluoroethylene (PTFE). In particular, the phase transition during the loading with subsequent tension are analysed using a two-phase rate sensitive material model implemented in the CTH hydrocode and the calculations are compared with experimental high-speed photography. The damage patterns and their link with the change of loading modes are analysed numerically and are correlated to the test observations. [Preview Abstract] |
Thursday, June 18, 2015 4:15PM - 4:30PM |
V3.00003: Experimental and Computational Investigation of the Shearing Resistance of an Elastomer at Pressures Up to 18 GPa and Strain Rates of $10^{5}-10^{6}s^{-1}$ Tong Jiao, Rodney Clifton Pressure-shear plate impact (PSPI) experiments have been conducted to study the mechanical response of an elastomer (polyurea) at high pressures and high strain rates. The previously determined isentrope has been extended to 18 \textit{GPa}. At this pressure, the high-strain-rate shearing resistance of polyurea is approximately 1 \textit{GPa}--comparable to, or greater than, that of high strength steels and at much lower weight. From the PSPI experiments it is evident that the shearing resistance of polyurea increases essentially proportionately with increasing pressure. Polyurea's response to volumetric changes is largely reversible whereas its response to distortional changes is largely dissipative. These effects are modeled by introducing a constitutive model that incorporates a finite deformation isotropic elasticity model for the instantaneous response and a quasilinear viscoelasticity model--with distributed relaxation times--to model relaxation from the instantaneous elastic response. In order to model a dependence of shear wave speed on pressure, the strain energy function for the instantaneous elastic response is comprised of a distortion-dependent term multiplied by a factor that depends only on the change in volume. This model has been implemented into Abaqus\texttrademark to simulate the response of polyurea P1000 under the impact conditions of a variety of PSPI experiments. Results of these simulations suggest that the main features of the experimental results can be explained by such a model. [Preview Abstract] |
Thursday, June 18, 2015 4:30PM - 4:45PM |
V3.00004: Characterization of Focal Muscle Compression Under Impact Loading Ben Butler, David Sory, Thuy-Tien Nguyen, Richard Curry, Jon Clasper, William Proud, Alun Williams, Kate Brown The pattern of battle injuries sustained in modern wars shows that over 70{\%} of combat wounds are to the extremities. These injuries are characterized by disruption and contamination of the limb soft tissue envelope. The extent of this tissue trauma and contamination determine the outcome in extremity injury. In military injury, common post-traumatic complications at amputation sites include heterotopic ossification (formation of bone in soft tissue), and severe soft tissue and bone infections. We are currently developing a model of soft tissue injury that recreates pathologies observed in combat injuries. Here we present characterization of a controlled focal compression of the rabbit flexor carpi ulnaris (FCU) muscle group. The FCU was previously identified as a suitable site for studying impact injury because its muscle belly can easily be mobilized from the underlying bone without disturbing anatomical alignment in the limb. We show how macroscopic changes in tissue organization, as visualized using optical microscopy, can be correlated with data from temporally resolved traces of loading conditions. [Preview Abstract] |
Thursday, June 18, 2015 4:45PM - 5:00PM |
V3.00005: On the response of \textit{Escherichia coli} to high rates of deformation Brianna Fitzmaurice, Jonathan Painter, Gareth Appleby-Thomas, David Wood, Rachael Hazael, Paul McMillan While a large body of work exists on the low strain-rate loading of biological systems such as bacteria, there is a paucity of information on the response of such organisms at high rates of deformation. Here, the response of a readily accessible strain of bacteria, \textit{Escherichia coli} (\textit{E. coli}), has been examined under shock loading conditions. Although previous studies have shown greatly reduced growth in shock conditions up to several GPa, relationships between loading conditions and bacterial response have yet to be fully elucidated. A more rigorous investigation into the 1D shock loading response of \textit{E. coli} has been carried out here, leading to a more comprehensive view of its behaviour when exposed to high pressures. Comparison has been drawn to provide insight into the importance of the nature of the loading regime to the survival of these biological systems. [Preview Abstract] |
Thursday, June 18, 2015 5:00PM - 5:15PM |
V3.00006: Novel method to dynamically load cells in 3D-gel culture for primary blast injury studies David Sory, Anabela Cepa-Areias, Darryl Overby, William Proud For at least a century explosive devices have been reported as one of the most important causes of injuries on battlefield in military conflicts as well as in terrorist attacks. Although significant experimental and modelling efforts have been focussed on blast injury at the organ or tissue level, few studies have investigated the mechanism of blast injury at the cellular level. This paper introduces an in vitro method compatible with living cells to examine the effects of high stress and short-duration pulses similar to those observed in blast waves. The experimental phase involved high strain rate axial compression of biological cylindrical specimens within a hermetically sealed sample holder made of a biocompatible polymer. Numerical simulations were performed in order to characterize the loading path within the sample and assess the loading conditions. A proof of concept is presented so as to establish a new window to address fundamental questions regarding primary blast injury at the cellular level. [Preview Abstract] |
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