Compression Testing

The parameters for compression tests include confine or unconfined compression and creep vs. failure tests, but once again there is no standard protocol [28-31]. The effect of fibre inclusion has been shown to increase in stiffness and the ability to bear high stresss. Inclusion of electrospun silk fibrin fibres in chitosan hydrogel using various test methods resulted in different compressive stiffness values being determined. The modulus calculated from the linear portion (i.e. elastic region) of a stress vs. strain profiles under static compressive loading for a homogeneously dispersed chopped silk fibrous within a chitosan hydrogel and a layer by layer assembled hydrogel-fibre composite were approximately 2 and 3 times stiffer when compared to the stiffness for pure chitosan hydrogel [28]. A biocomposite consisting of polyacrylamide gel and short chitosan nanofibres sustained seven times higher stress when compared to pure polyacrylamide at 95% compressive strain and recovered to its original height on load removal [32]. These observed improvements in mechanical properties were due to the fibres preventing crack growth within the microstructure and the smooth transfer of stress between the hydrogel matrix to the fibres.

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