  Thermoplastic polyurethanes (TPU) are block copolymeric materials composed of
plastomeric "hard" and elastomeric "soft" domains, by which they exhibit highly
resilient yet dissipative large deformation features depending on volume
fractions and microstructures of the two distinct domains. Here, we develop a
new methodology to address the microscopic deformation mechanisms in TPU
materials with highly disordered microstructures. We propose new
micromechanical models for randomly dispersed (or occluded) as well as randomly
continuous hard domains, each within a continuous soft structure as widely
found in representative TPU materials over a wide range of volume fractions,
v$_{\mathrm{hard}}$ = 26.9% to 52.2%. The micromechanical modeling results are
compared to experimental data on the macroscopic large strain behaviors
reported previously (Cho et al. 2017). We explore the role of the dispersed vs.
continuous nature of the geometric features of the random microstructures on
shape recovery and energy dissipation at the microstructural level in this
important class of phase-separated copolymeric materials.
