Considerations on constitutive modelling of soft connective tissues with regard to damage phenomena

The investigation of biomechanical response of biological tissues entails a deep knowledge of the constituent materials, by means of experimental testing in direct relation with the numerical modelling, just working within a reciprocal validation procedure. The definition of constitutive models represent, within the numerical formulation of the problem, a fundamental task, performed using different techniques based on combination of analytical, numerical and experimental approaches. In particular, micro structural arrangement of the materials involved in the analysis must be considered to define a phenomenological model, where different components are considered together with their reciprocal interaction. In the case of degenerative conditions, due to aging or pathologies, the formulation to be adopted becomes more complicated, mostly because the tissues undergo phenomena that must be considered within damage theory. In the present work the constitutive formulation is based on the hyperelastic model, that represents a strong framework to interpret typical soft connective tissues non linear mechanics, considering elasto-damage effects by adopting a specific procedure. In particular, anisotropic elasto-damage constitutive models are developed for the analysis of periodontal ligament and tendons. The reliability of the models developed is evaluated by the comparison of experimental and numerical results.