Deformation tracking of truss lattices under dynamic loading based on Digital Image Correlation

Abstract

Three-dimensional (3D) truss-based metamaterials (or architected materials) have been the subject of an increasing amount of studies, owing to their impressive and tunable mechanical properties. Unfortunately, experimentally studying their mechanical multiscale behavior under dynamic loading presents a challenge due to the complex time-dependent correlation between the overall truss response and the deformation of individual beams and beam junctions. Tracking the time-dependent deformation of 3D-printed low-density trusses is challenging for traditional techniques such as Digital Image Correlation (DIC), owing to the discrepancy between typical feature (strut) sizes and the field of few of the overall truss, further difficulty in applying speckle patterns, as well as the lack of a stable bright background during testing—especially when high rates and large 3D deformation are involved. As a remedy, we present an efficient DIC-based technique, which admits tracking the nodal displacements of points of interest (such as, e.g., the strut junctions) in periodic and non-periodic truss networks across a range of loading rates. We use this technique to identify the time-dependent nodal displacements of different truss architectures, whose large deformation is of interest for energy absorption capabilities of truss metamaterials. The quality of results is assessed by performing multiple trackings on each truss topology, which reveals that errors are negligible for the reported range of conditions.