Elham Naghashzargar

Tendon and ligament tissue injuries are one the most common body injuries. Engineered tissues are expected to have similar features and biomechanical variable factors, such as mechanical properties, as well as a viscoelastic behavior like native tissues. The aim of this study was to investigate the mechanical properties and stress-relaxation behavior of silk yarns as the primary material in designing different types of tendons and ligaments tissue scaffolds. For this purpose, multilayer silk yarns were prepared experimentally by changing the number of twists and layers. Then, linear and nonlinear standard solid CRE and stress-relaxation models were selected and simulated considering the physical and physiological properties of the desired tissue. As a general conclusion, the CRE curve shape and details were similar to the actual tendon and ligament CRE curve shape with increasing the number of twists and layers. The results also showed that the force in specific time tended to decrease; as well, there was the reduction of stress in the early stages of the CRE test because of the increase in the number of twists and layers. Also, the stress-relaxation analysis showed that by increasing the number of twists and layers, the absolute initial discharge curve slope of the stress and maximum discharge level was decreased due to increase in the elasticity of the samples. Comparisons of linear and nonlinear CRE model showed no statistically significant difference. So, the linear model was selected as the simpler one with less computation and complexity. Finally, there was a good agreement between the model and experimental results for CRE and stress-relaxation.