Research Of Microscopic Network Model Of PVA Hydrogel Based On Uniaxial Tension

In recent years,hydrogel has attracted extensive attention due to its excellent biocompatibility,high water content and high flexibility.It has been proved to be a potential soft material in biomedical,tissue engineering,drug delivery and other frontier areas.The micro fiber network structure determines its macroscopic mechanical behavior.so the research of hydrogel micro structure has great value.In this paper,we use polyvinyl alcohol(PVA)hydrogel,which is widely used in cartilage replacement,as the research object.Firstly,it's uniaxial quasi-static tensile behavior was studied.Based on this,a microscopic network model of random distribution of fibers was proposed.The model can be consistent with the tensile test curve of PVA hydrogel with different fiber content,which confirms the reliability of this model Furthermore,we analyzed the microscopic fiber network model,and reveal the microscopic mechanism of a series of macroscopic mechanical behaviors of hydrogel materials.The main contents of this paper are as follows(1)In view of the defects of uniaxial tensile tests of soft hydrated materials,we proposed a new hydrogel uniaxial tensile test technique without clipping.The rationality of the technique is verified with the finite element method.We measured the uniaxial tensile stress-strain curves and tensile strength of PVA hydrogels with different fiber contents by this method.And we used the constitutive equations of polymer elastomers proposed by Wall and Flory to preliminarily study the tensile behavior of PVA hydrogel(2)A micro network model of fiber random distribution is proposed.The parameters of the model are determined by means of instrument observation,calculation and analysis.The results calculated by the finite element method show that the model can be consistent with the tensile test results of PVA hydrogels with different fiber contents when the parameters remain unchanged.Then we got a important parameter of PVA hydrogel,which is difficult to be experimentally measured,that the density of crosslinks varying with the fiber content(3)A series studies of microscopic mechanism have been carried out through our micro fiber network model.It confirmed that the chain effect caused by stress redistribution of hydrogel fibers is the reason for the instantaneous breakage of hydrogels.We also analyzed the influence of orientation degree(Alignment)on the macroscopic tensile modulus of hydrogels,and the change of pore size of PVA hydrogels during tensile process.