On the mechanics of networked type II collagen: Experiments, constitutive modeling, and validation

In this study we investigate the mechanics of type II collagen fibrils, an essential structural component in many load-bearing tissues including cartilage. Although type II collagen plays a crucial role in maintaining tissue integrity, the stress–stretch and failure response of type II collagen fibrils in tension is not established in the current mechanics literature. To address this knowledge gap, we conducted tensile tests on isolated collagen networks from articular cartilage and established a validated constitutive model for type II collagen fibril. We identified two distinct failure mechanisms: one without softening before failure and another with pronounced softening. Our findings reveal that network morphology significantly influences the bulk mechanical response, providing a framework for modeling the complex behavior of collagen fibrils in both healthy and diseased tissues. The validated model enhances the accuracy of finite element models used in analyses of soft tissues and may deepen our understanding of the mechanical progression of diseases like osteoarthritis. Our results offer valuable insights into the mechanics of type II collagen, with implications for improving computational models and for guiding future studies in tissue regeneration and disease treatment.