Thermo-Mechanical Response of an Additively Manufactured Energetic Material Simulant to Dynamic Loading
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S.I. : IMPACT MATTERS: K.T. RAMESH’S 60TH BIRTHDAY
Thermo‑Mechanical Response of an Additively Manufactured Energetic Material Simulant to Dynamic Loading A. Keyhani1 · M. Zhou1,2 Received: 16 March 2020 / Accepted: 17 September 2020 © Society for Experimental Mechanics, Inc 2020
Abstract The mesoscale thermo-mechanical behavior of an additively manufactured energetic material (AMEM) simulant under dynamic loading is studied. The material is unidirectionally printed using direct ink writing (DIW) of a high solid-loaded photopolymer and cured under ultraviolet (UV) light exposure. Experiments and multi-physics computations are performed to relate localized deformation, dissipation mechanisms, and temperature rises to the print structure. Simultaneous high-speed visible light and infrared imaging is used to obtain deformation and temperature fields over the same area of samples with micrometer spatial and microsecond temporal resolutions. Loading along different directions relative to the print structure of the material is achieved using a split-Hopkinson pressure bar (SHPB) or Kolsky bar at the average strain rate of ~ 310 s−1. Shear banding and shear failure are observed. Simulations accounting for the geometry and print structure of the samples are performed. The microstructural heterogeneities are found to significantly affect the orientation-dependent deformation, damage, and heating, with the damage and heating most pronounced when the loading direction and print orientation are non-collinear. The heating is attributed to both constituent inelastic dissipation and internal friction. Depending upon the strain rate level and the loading orientation, the contribution of frictional dissipation to the overall heating is 0.9–4.5%. Despite this relatively low fraction in the overall heating, friction is localized at fracture sites and plays an important role in the development of local temperature spikes called hotspots which are of great interest for energetic materials. Keywords Additively manufactured energetic material (AMEM) · Split-Hopkinson pressure bar (SHPB) · High-speed optical and infrared imaging · Digital image correlation (DIC) · Multi-physics finite element simulation
Introduction The geometric flexibility provided by additive manufacturing (AM) or 3D-printing opens new avenues for functionally tailoring materials for specific applications. As a result, AM has been widely used to produce a wide range of materials such as metals [1, 2], polymers [3], and energetic materials (EM) [4, 5]. Several AM techniques have been used for EM including electrospray deposition (ESD) [6–8] and direct ink writing (DIW) [9–12]. AM processes result in embedding inherent heterogeneities that can lead to poor mechanical * M. Zhou [email protected] 1
The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332‑0405, USA
School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332‑0405, USA
2
properties [13, 14] and different mec
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