Effect of liquid environment on dynamic constitutive response of reinforced gels

Abstract

Quasi-static and dynamic compressive behavior of three different types of hydrogels used for soft tissue applications are tested using a modified split Hopkinson pressure bar. Three kinds of hydrogels: (a) Epoxy hydrogels, (b) Epoxy hydrogels reinforced with definite orientation of three-dimensional polyurethane fibers and (c) fumed silica nano particles reinforced hydrogels with different weight fractions are considered in this study. Swellability of the all the hydrogels considered are studied and controlled by mixing different ratios of jeffamines and epoxides. The three dimensional pattern of the fibers are generated by a rapid robo-casting technique. Split Hopkinson pressure bar (SHPB) was used for dynamic loading and a pulse shaping technique was used to increase the rising time of the incident pulse to obtain dynamic stress equilibrium. A novel liquid environment technique was implemented to observe the dynamic behavior of hydrogels when immersed in water. Experiments were carried out at dynamic loading conditions for different strain rates with and without water environment. Results show that the hydrogels are rate sensitive. Also the yield strength of hydrogels decreased and elongation percent increased when they were immersed in water.