Research On Large Coupled Deformation Behavior Of Smart Hydrogel

Smart responsive hydrogel is a typical smart soft material.It can be considered as a stable system of hydrophilic polymer three-dimensional network structure combined with water molecules in a water-rich environment.When the smart responsive hydrogel is stimulated by electrochemical environment,the chemical field and temperature field can induce the large deformation behavior of the material.On the other hand,the mechanical load will also affect the physical field inside the gel.The large deformation behavior of smart hydrogels in the thermo-chemo-mechanical coupling field is studied and the hybrid multi-fields coupling free energy is derived.The phase transition and buckling of hydrogel devices during large deformation are studied and smart responsive hydrogel metamaterials are designed and prepared.The main contents of this dissertation are as follows:(1)A static equilibrium model considering the network structure of hydrogel and the evolution of the statistical mechanical properties of the chain segment was established.For the polyelectrolyte hydrogel,the effects of the three-dimensional polymer network and entanglement effect of slipping chains on the macrochemomechanical coupling properties and the gauss transition when the hydrogel deformed are considered.A new free energy density function is constructed and a static equilibrium model is established.The computational results show that the microstructure parameters of the network segment have an important effect on the mechanical behavior by analytical method.(2)A numerical method for the analysis of chemo-mechanical coupling nonuniform large deformation of smart hydrogel materials and devices is developed.Based on free energy of the hydrogel and the ABAQUS finite element software platform,the user subroutine was used to develop the corresponding numerical calculation method of chemo-mechanical coupling super-large deformation.The non-uniform large deformation of structures and devices of several intelligent hydrogel in a chemomechanical coupling field is simulated by the developed numerical method.(3)The analytical solution of the phase change temperature range of the thermosensitive hydrogel is derived and a program is developed to get the exact phase change temperature.For the specific thermo-sensitive hydrogel,the correctness of solution is verified by contrasting the phase temperature measured by the traditional experiments.By establishing the relationship between the steady state and the free energy,the accurate phase transition temperature was calculated by means of programming,and the influence of the microstructural parameters on the phase transition temperature was discussed.The bistable phenomenon during phase transition is simulated by FEM.(4)The buckling and instability of smart hydrogel films are investigated.Firstlly,the analytical solution of the critical condition for the delamentless surface buckling of hydrogel/elastic matrix structure in the chemo-mechanical coupling field is got,and the influence of the microstructure on the buckling is discussed.Then the buckling modalities are simulated by numerical method,and the effects of structure and material parameters on the buckling are discussed.Finally,the bifurcation phenomenon of the porous hydrogel film is simulated by finite element method.(5)A metamaterial with negative swelling effect driven by chemical potential energy is designed and prepared through combining the smart responsiveness of hydrogels with the deformation mechanism of chiral metamaterials.The deformation property of 4D printed composite structure is used to transform the swelling deformation of hydrogel into the bending deformation of flexible ligament,and the volume of the metamaterial reduces.By the excitation of chemical field of external solution,large and adjustable effective negative expansion behavior can be obtained,as well as ideal isotropic characteristics.Based on the experimental data and the finite element model,by adjusting the material parameters and structural parameters,the customized metamaterial can be realized to produce the ideal negative expansion deformation.The work in this dissertation is helpful to understand and explain the mechanism of large deformation of smart responsive hydrogels in coupled multi-physical fields,predict the coupling deformation behavior of hydrogels,and guide the preparation and application of hydrogels.The developed numerical simulation platform also has important application value for the design and optimization of intelligent soft devices and devices with complex structures.