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2 Acta of Bioengineering and Biomechanics

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Mechanical properties variation and constitutive modelling of biomedical polymers after sterilization

Zanelli L., Todros S., Carniel E. L., Pavan P. G., Natali A. N.

Acta of Bioengineering and Biomechanics

2017

Vol. 19, no. 3

3--9

Purpose: In this work, the mechanical behavior of two block copolymers for biomedical applications is studied with particular regard to the effects induced by a steam sterilization treatment that biomedical devices usually undergo in healthcare facilities. This investigation is aimed at describing the elasto-plastic behavior of the stress-strain response, determining a functional dependence between material constitutive parameters, to obtain an optimal constitutive model. Methods: The mechanical properties of these polymers are analyzed through uniaxial tensile tests, before and after the sterilization process. The effect of sterilization on the mechanical behavior is evaluated. The Ramberg-Osgood model is used to describe the elasto-plastic behavior of the stress-strain response. Results: Data from uniaxial tensile tests are discussed in the light of previous data on the same polymeric materials, in order to highlight the correlation between physicochemical and mechanical properties variation. The material constitutive parameters are determined and the functional dependence between them is found, thus enabling an optimal constitutive model to be obtained. Conclusions: The effect of sterilization on the material constitutive parameters is studied, to evaluate the suitability of the model in describing the mechanical response of biomedical polymer before and after sterilization treatment. The same approach can be applied to other biomaterials, under various tensile tests, and for several processes that induce variation in mechanical properties.

Investigation of the biomechanical behaviour of articular cartilage in hindfoot joints

Venturanto C., Pavan P. G., Forestiero A., Carniel E. L., Natali A. N.

Acta of Bioengineering and Biomechanics

2014

Vol. 16, no. 2

57--65

Numerical models represent a powerful tool for investigating the biomechanical behavior of articular cartilages, in particular in the case of complex conformation of anatomical site. In the literature, there are complex non-linear-multiphase models for investigating the mechanical response of articular cartilages, but seldom implemented for the analysis of high organized structure such as the foot. In the present work, the biomechanical behavior of foot cartilage is investigated by means of a fiber-reinforced hyperelastic constitutive model. The constitutive parameters are obtained through the comparison between in vitro experimental indentation tests on cartilage and numerical analysis data interpreting the specific experimental conditions. A finite element model of the hindfoot region is developed. Particular attention is paid to model cartilage in order to respect its morphometric configuration, including also the synovial capsule. The reliability of the procedure adopted is evaluated by comparing the numerical response of tibio-talar joint model with in vivo experimental tests mimicking the foot response in stance configuration.