Quasi-Static and High Strain Rate Simple Shear Characterization of Soft Polymers
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The simple shear response of soft polymers under large deformation (>50%) and strain rates spanning 10−3 – 103 s−1 is characterized by developing quasi-static and split-Hopkinson pressure bar based single-pulse dynamic simple shear experiments rooted in continuum mechanics fundamentals. Cross-linked polydimethylsiloxane (PDMS) is chosen as a model material. By examining the evolution of stress, strain and strain rate, the latter two parameters measured using two-dimensional digital image correlation (DIC), it is demonstrated that dynamic simple shear deformation consists of four distinct stages: momentum diffusion, inertia effect, steady-state material response, and strain rate decay. By isolating the unsteady and steady-state deformation stages, inertia-free material response is captured under a uniform strain rate. It is shown that the shear response of PDMS is nearly linear with a weakly rate-sensitive shear modulus in the investigated strain rate range. Further, by analyzing the DIC strain-field and comparing the kinematic experimental results with those predicted by classical continuum mechanics, it is demonstrated that the proposed experiments not only achieve a nearly theoretical simple shear state that is uniform across the specimen, but also allow for post-test validation of individual experiments based on these criteria.
KeywordsPDMS Simple shear Large deformations Strain rate sensitivity Split-Hopkinson pressure bar (SHPB) Digital image correlation (DIC)
This research was supported by the National Science Foundation under Grant Nos. CMMI-1634188 and CMMI-1762791 to the University of Florida, Gainesville, USA.
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