ELASTIC AND HYPERELASTIC PROPERTIES OF THE HUMAN NAIL PLATE

Abstract

Introduction. As is known, changes in the nail, as an appendage of the skin, can be genetically determined, caused by injuries, diseases, medications or exposure to harmful substances. Installation of partial or complete dentures may be required for any form of growth disorder of the nail plate (onychodystrophy). Prosthetics can act as a means of masking nail abnormalities. In all these cases, knowledge of the mechanical properties of both the replacement materials and the nail plate itself is necessary. However, the latter have not been fully studied; there is no detailed knowledge about the elastic and hyperelastic characteristics of the biomaterial. The aim of the study. The mechanical properties of the human nail plate are compared with elastic and hyperelastic models of continuum mechanics (large deformations). Methods. Experimental σ-ε curves obtained from literature data were used. The computer algebra system Mathcad 15.0 and the multifunctional finite element analysis package ANSYS 2022 R2 were used. Results. The parameters of the linear and 6-hyperelastic models were calculated and their correspondence to the initial data was determined. Among hyperelastic models, the 5-parameter Mooney–Rivlin model and the 2nd order polynomial model are best suited to describe the mechanical properties of the nail plate. These models have the highest correlation coefficient R=0.98 and the following statistical indicators SD=0.005 GPa, δmax=0.011 GPa, δ=12.93%. The greatest discrepancies between the experimental and model data were demonstrated by the Ogden model of the 1st order nail plate (R=0.84) and the simplest hyperelastic neohookean model (R=0.86). The stability of the models (dσ/dε sign) at small deformations was studied. Conclusion. The results obtained can be useful for podiatrists involved in the development of methods for restoring nail plates using artificial replacement materials and are recommended for use in nail tissue engineering.