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No abstract

The performance of energetic materials subjected to dynamic loading significantly depends on their micro- and meso-scale structural morphology. The geometric versatility offered by additive manufacturing opens new pathways to tailor the performance of these materials. Additively manufactured energetic materials (AMEMs) have a wide range of structural characteristics with a hierarchy of length scales and process-inherent heterogeneities, which are hitherto difficult to precisely control. It is important to understand how these features affect AMEMs’ response under dynamic/shock loading. Therefore, temporally and spatially resolved measurements of both macroscopic behavior and micro- and meso-level processes influencing macroscopic behavior are required. In this paper, we analyze the shock compression response of an AMEM simulant loaded under several impact conditions and orientations. X-ray phase contrast imaging (PCI) is used to track features across the observed shock front and determine the linear shock velocity vs particle velocity equation of state, as well as to quantify the interior deformation fields via digital image correlation (DIC) analyses. Photon Doppler velocimetry is simultaneously used to measure the particle velocities of the specimens, which are consistent with those obtained from x-ray PCI. The DIC analyses provide an assessment of the average strain fields inside the material, showing that the average axial strain depends on the loading intensity and reaches as high as 0.23 for impact velocities up to 1.5 km/s. The overall results demonstrate the utility of x-ray PCI for probing “in-material” equation of state and interior strains associated with dynamic shock compression behavior of the AMEM simulant.

The dynamic tensile spall failure of additively manufactured (AM) two-layered bimetallic GRCop-84—Inconel® 625 alloys, with planar and slanted interfaces, is investigated using uniaxial-strain plate-impact gas-gun experiments. Multiple photon Doppler velocimetry (PDV) is used to monitor the back (free) surface velocity profiles and to determine the influence of the interface geometry on the spall failure. Micrographs of cross sections of recovered impacted samples reveal failure along the interface as well as in-material regions. Spall strengths determined from pull-back signals captured with the use of the multiple PDV probes illustrate different location-specific values for the same sample, corresponding to failure occurring in Inconel® 625, or GRCop-84, or along their interface, depending on the geometry of the interface. The results obtained from the experiments employing multiple PDV probes correlated with microstructural observations of cross sections of recovered impacted samples, provide a useful method for determining the complex spall failure response of two-layered bimetallic alloys, including the differentiation of the response of the respective alloy materials relative to that of the interface, in the same experiment.