Experimental Investigation of Tear Strength, Stress Relaxation, and Anisotropy of Polypropylene Surgical Meshes

In this study, the mechanical behavior of polypropylene surgical meshes was investigated with a focus on tear strength, stress relaxation, and anisotropy. Four commercially available meshes with different structural architectures and grammages were tested. Mechanical characterization was performed by means of trouser tear tests and stress relaxation tests conducted for 1 h at a constant strain of 20%. Tear strength, secant stiffness, apparent Young’s modulus, initial and residual stresses, and normalized relaxation response were determined, and the anisotropic behavior of the meshes was evaluated in two orthogonal directions. Significant differences were observed among the investigated meshes. Materials with higher grammage and more compact structures exhibited greater tear strength, whereas lighter meshes showed lower strength and increased susceptibility to tear propagation. All meshes demonstrated pronounced viscoelastic behavior, characterized by an initial rapid stress decay followed by slower relaxation processes and gradual stabilization. The absolute stress response and stiffness were strongly dependent on mesh structure and loading direction, whereas normalized stress relaxation parameters were largely independent of orientation. The combined evaluation of tear resistance and time-dependent mechanical response highlights the importance of structural parameters and anisotropy in determining the performance of surgical meshes. These findings contribute to a better understanding of mesh mechanical behavior and may support the optimization of mesh design and the development of implants with improved durability and mechanical reliability under physiological loading conditions.