A hybrid method to characterise the mechanical behaviour of biological hyper-elastic tissues

The characterisation of biological tissues has become high interest area in recent years, due to the grow uses and development of artificial soft tissues implants. These tissues present a nonlinear mechanical behaviour, which highly differs from typical engineering materials. This aspect brings us an enormous difficulty in characterisation of soft tissues and thus required the development of new experimental techniques associated with new numerical algorithms. This work presents the mechanical characterisation of human vaginal mucosa based on a hybrid technique that combines the experimental measurement of displacement field, acquired during a tensile test with numerical simulation, using material constitutive laws. The digital image correlation technique was used for high spatial resolution measurement of the displacements field on the hyper-elastic biological tissues. Several numerical simulations were carryout based on finite element commercial package, Ansys®, by combining the experimental displacements with different hyper-elastic models, which were developed from the experimental tensile test. Fluid release from specimen was observed during the tensile test, producing speckle decorrelation and, therefore, lack of information in displacement field. This problem was overcome by extrapolating data at the boundaries, through the application of special algorithm developed by the authors. The proposed hybrid method is shown to be more acquired then the numerical method based only on material constitutive models