Yousef Heider

Assessment of the viscoelastic mechanical properties of polycarbonate urethane for medical devices

The underlying research work introduces a study of the mechanical properties of polycarbonate urethane (PCU), used in the construction of various medical devices. This comprises the discussion of a suitable material model, the application of elemental experiments to identify the related parameters and the numerical simulation of the applied experiments in order to calibrate and validate the mathematical model. In particular, the model of choice for the simulation of PCU response is the non-linear viscoelastic Bergström-Boyce material model, applied in the finite-element (FE) package Abaqus®. For the parameter identification, uniaxial tension and unconfined compression tests under in-laboratory physiological conditions were carried out. The geometry of the samples together with the applied loadings were simulated in Abaqus®, to insure the suitability of the modelling approach. The obtained parameters show a very good agreement between the numerical and the experimental results.

A NANO-MACRO BOTTOM-UP APPROACH TOWARDS BRITTLE FRACTURE

A novel combined method for highly brittle materials, which provides an efficient and accurate insight into multi-scale fracture modeling, is proposed. In particular, physicallymotivated molecular dynamics simulations are performed to predict crack propagation, in the nanoscale, and therewith determine material and other parameters required for the macroscale modeling under a phase-field continuum approach. The proposed computational approach, which does not require any empirical parameters, contributes towards an improved understanding of mechanics at all length-scale levels.