Full-Field Deformation Measurements in Liquid-like-Solid Granular Microgel Using Digital Image Correlation

This paper presents the experimental characterization of the in-plane deformation field at any depth within a granular support medium (GSM) called Carbomer 940 using digital image correlation (DIC) and particle image velocimetry (PIV). A method was developed to produce a 2D plane of randomly shaped speckles within the GSM for DIC. Four different needle diameters and four different speeds were used as test specimens representative of those utilized for 3D printing of soft matter in the GSM. The results can be used to determine dimensional tolerances and assessing interactions between multiple injection needles and acceptable spacing. The displacements in the direction of needle motion (u) and transverse (v) were obtained. Subsequently, the magnitudes were determined as a function of distance from the needle path and time history. Results show that near the needle there is a region of yielded/fluidized material and away from the needle path the material acts like a viscoelastic solid. Permanent deformation decreases with increased distance from the path and recovery is enhanced by reversing back through the path.