SHPB experimental method for ultra-soft materials in solution environment

Abstract

Biological soft tissues usually perform physiological functions in solutions, and the mechanical properties of the bio-soft matters in air and solution may differ from that in solution, but the measurement technique of the dynamic mechanical properties of ultra-soft materials in solution is still an unexplored realm. In order to develop a feasible method to test ultra-soft materials in solution by the split Hopkinson pressure bar (SHPB) technique, this paper uses the liquid silicone rubber (LSR) whose property is seldom affected by water and the purified water as a testing material and a solution, respectively. The double-striker electromagnetic driving SHPB system, which has been designed for ultra-soft materials, is adopted to carry out dynamic test for LSR in solution, meanwhile the testing process was recorded by a high-speed digital camera. The tests include three cases named as: Specimen in air, No specimen in water, Specimen in water. Specimen in air was set as a reference; No specimen in water was used to learn the mechanism of load transferring of the water and to set the correction of the effect of the water; Specimen in water was the standard test in water whose results must be modified for the characterization of materials. The high-speed images show that the water may be regarded as a steady flow until the constant strain rate loading ended. Based on such phenomenon and the unchanged volume of specimen and by simplifying the description of the flow field, a data correcting method was set up on the basis of the deduction of both the specimen deformation and fluid flow field to modify the experimental result tested in water. According to the comparison, experimental result in air shows good agreement with corrected result in solution, indicating the feasibility of our recommended method for the SHPB tests in solution. In this way, our research is of great significance in laying an important foundation in the new academic field of the dynamic mechanical behaviors of bio-soft matters in solution.