Micromechanical Models of Helical Fiber Organization in Crimped Tendon and Ligament Fibers Predict Large Poisson’s Ratios

The Poisson’s ratio is a measure of how much lateral contraction occurs in response to a uniaxial tensile strain, therefore making it a metric of the volumetric behavior of a material. A Poisson’s ratio greater than 0.5 for an isotropic material subjected to uniaxial tension is indicative of volume loss, which in the scheme of biphasic theory is believed to be manifested as fluid exudation. Experimentally obtained values for the Poisson’s ratio range from 0.8 in rat tail tendon, 1.3 in capsular ligament to 3.0 in flexor tendon [1,2,3]. In spite of the important implications of this volumetric response the micromechanical origins of these large Poisson’s ratios have been largely uninvestigated.