Understanding mechanical failure, crack propagation, and compressive behavior at the sub-micrometer scale is essential for tailoring material properties for structural performance. Additive manufacturing allows for the controlled morphology of materials to more directly probe this performance. Hyper elastic materials have structures and mechanical responses to deformation at several size scales, and also have a dynamic response that cannot be paused during loading. Using both laboratory-based, and synchrotron-based 3D tomographic imaging, the examination of deformation and damage on several size and time scales is critical to understanding how these soft materials behave. The application of laboratory-based nano-scale CT imaging to small structures and individual ligaments is used to investigate print quality including voids, layer adhesion and print accuracy. Laboratory-based micro CT is used to investigate print accuracy on the meso scale as well as damage mechanisms. Synchrotron-based micro CT is used to image materials during deformation, a high imaging rate examinations the material before any stress relaxation from the mechanical response becomes apparent and can be used to illustrate damage pathways. Advanced processing is required to understand these mechanical responses. The use of eigenvector centrality predicts the mechanical properties of lattice-structured materials as a function of structural completeness and digital volume correlation can be used to understand the stress fields within materials during deformation. Eigenvector centrality applies a straightforward scaling argument in combination with a free energy defined by the principle eigenvector of the adjacency matrix that encapsulates the network’s connectivity which provides a ranking of the relative connectivity-importance of different nodes within a network. In principle, it is possible to calculate how the modulus of an elastomer changes as bonds of different types (chemical or physical) are added to or deleted from the <i>specific</i> structural configuration. High speed synchrotron imaging during uniaxial tension measurements, not only allows for the imaging of adhesion between the polymer and glass micro beads within a composite, but also the beads act as internal fiducials for the 3D mapping of strain fields using digital volume correlation. These two techniques enhance the information provided by the 3D images for a better understanding of structure and how these materials respond.

X-ray tomographic imaging of mechanical deformation at various length and time scales

253rd National Meeting (2017)

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