  The biomechanical properties of blood clots, which are dictated by their
compositions and micro-structures, play a critical role in determining their
fates, occlusion, persistency, or embolization in the human circulatory system.
While numerous constitutive models have emerged to describe the biomechanics of
blood clots, the majority of these models have primarily focused on the
macroscopic deformation of the clots and the resultant strain-stress
correlations without depicting the microscopic contributions from their
structural components, such as fibrin fibers, fibrin network and red blood
cells. This work addresses the gap in current scientific understanding by
quantifying how changes in the microstructure of blood clots affect its
mechanical responses under different external stresses. We leverage our
previous published work to develop a hyperelastic potential model for blood
clots, which incorporates six distinct strain-energy components to describe the
alignment of fibers, the entropic and enthalpic stretching of fibrin fibers,
the buckling of these fibers, clot densification, and clot jamming.These
strain-energy components are represented by a combination of simple harmonic
oscillators, one-sided harmonic potentials, and a Gaussian potential. The
proposed model, which is C0, C1, and C2 continuous with a total of 13
parameters, has been validated against three data sets: fibrin clot in tension,
blood clot in compression, and blood clots in shear, demonstrating its
robustness. Subsequent simulations of a microscopic blood clot model are
performed to uncover mechanistic correlations for a majority of the
hyperelastic potential's stiffness/strain parameters. Our results show that
only one proposed term concerning fiber buckling needs further refinement,
while the remaining five strain-energy terms appear to describe precisely what
they were intended to.
