Effects of Canine Paw Pad Morphology on Nonlinear Mechanical Behavior and Cushioning Performance

The paw pad is an outstanding cushioning structure, which demonstrates nonlinear mechanical characteristics when subjected to pressure. Nonlinear mechanical characteristics are generally considered to be related to the viscoelastic properties of the material. However, the relationship between its nonlinear mechanical properties and the morphological characteristics of the paw pad remains unknown. In this study, morphological data, mechanical data, and finite element simulation methods were integrated to explore how the unique shape of the paw pads enables them to exhibit excellent cushioning performance. The research findings indicate that the paw pad exhibits an irregular morphology. Nevertheless, its cross-sectional area increases in proportion to the increase in the paw pad height, presenting a linear gradient relationship (R2 = 0.99). Two comparison models with the same volume and height but different morphologies as the paw pad model, were designed for finite element simulation. The finite element static analysis shows that the influence of morphology is mainly reflected in the early deformation process, while the influence of viscoelastic material properties is reflected in the later load-bearing capacity. The finite element dynamic analysis shows that compared with the comparison models, the paw pad model has a more stable force during the impact process, without an instantaneous impact force at the initial contact moment. Moreover, the peak normal ground reaction force (GRF) component under different impact speeds is lower than that of the comparison models, demonstrating better buffering effects. The research results can provide inspiration and a biomechanical basis for the morphological design of buffering units.