Estimates Dynamic Material Properties of Ligaments under the Fast Strain Rate

The cyclic mechanical property of ligament plays an important role in biomechanics. If the microstructural volume fractions, orientations, and interactions among components for different ligament types are understood, it is conceivable to develop a general ligament model that is based on microstructural properties. But the cycle loading experiment is very difficult to operate, for convenience we can use the relationship between the complex modulus and relaxation modulus. Thus, in order to characterize the comprehensive viscoelastic behavior of cervical spine ligaments within their physiological range, the mechanical response of three types of human cervical spines: the anterior longitudinal ligament, the posterior longitudinal ligament and the ligamentum flavum and a porcine posterior longitudinal ligament collagen fascicles were simulated using quasi-linear viscoelastic theory model using the data from stress relaxation experiments at fast strain rate. A seven parameter model was investigated, which is sufficient to characterize the ligament dynamic material properties. Such model used the instantaneous elastic functions approximated as linear under fast strain rate. Dynamic material properties including storage modulus, loss modulus, the dynamic modulus of elasticity and the internal damping were investigated by transforming the stress relaxation data into frequency domain by Laplace transformation.