Microstructural and damage parameter effect analysis on the failure mechanism of fibrous soft tissues with a structure-based unit cell model

The presence of hierarchical microstructures in natural materials, such as connective tissues, makes them possess exceptional mechanical performance and undergo complex damage behaviors. Accordingly, in this study, a structure-based unit cell model (UCM) in which controllable irregular crimped fiber is embedded into soft matrix is constructed for the analysis of microstructural effects. An anisotropic hyperelastic constitutive model enhanced with different damage parameters is applied in finite element program, and the effects of damage parameters on the mechanical responses of fibrous soft tissues are investigated. The numerical results indicate that the fiber waviness plays a significant role in determining the stiffness of the tissues and that the microstructure controlled by the fiber crimp amplitude H, waviness chi and number of inflection points omega, mainly determines the fluctuation of the nominal stress-strain curves of these tissues with damaged fibers. In addition, a damage parameter analysis indicates that the attenuation of the strength and amplitude of the stress strongly depend on the strain energy limiter, and the parameter m mainly determines the rate of damage accumulation by the fibers with smaller strain energy limiters. The results of this study deepen the understanding of the mechanical behaviors of such fibrous soft tissues and provides a template for the optimization of structural and material designs for bioinspired composites.