The Thermodynamic Model Of SMP Substrate/Film Self-Assembled Plates And Instability Morphology Regulation

The film-substrate composite structure is a kind of material with special function which is covered by one or more layers.However,there are some main problems in the research:the self-assembly function of film-substrate structure is often one-way,that is,the structure can be developed from the smooth surface to the formation of complex surface buckling pattern by external stimuli.However,it is difficult to achieve the spontaneous change from the complex surface buckling morphology to smooth surface structure,which largely limits the potential application of the system.Firstly,the research status of shape memory polymers and the theoretical basis and research status of film-substrate composite structures are introduced.Then the buckling deformation SMP plates with different transition temperatures are analyzed theoretically by using the viscoelastic polymer theory.Finally,the reversible transition from smooth surface to structural buckling and then to smooth surface is simulated by computer numerical analysis.Then,a large number of numerical simulations are carried out to study the effects of substrate thickness,film thickness and elastic modulus ratio on the buckling behavior.Meanwhile the control factors of buckling morphology are analyzed qualitatively.The research results are of great significance to the realization of shape memory polymer and its application in the field of surface engineering science and technology.The results show that:(1)When the thickness of the substrate is greater than a certain value,the critical strain and wave length of the buckling wave are not affected,so the shape of the buckling wave is independent of the thickness of the substrate.(2)The thickness of the film has no influence on the critical strain of the buckling,which is consistent with the result of the film thickness in the theoretical formula,that is to say,the rationality of the theoretical critical strain formula is verified.(3)The critical wavelength of the membrane structure is approximately linearly related to the film thickness,and the error between the simulated results and the theoretical solutions is small.According to the theoretical formula,the wavelength can be changed by adjusting the thickness of the film,and then the wave number is changed in a certain length so as to control the shape of the buckling.(4)According to the formula of critical strain theory,the critical strain of buckling can be predicted by the elastic modulus ratio of membrane based material.(5)The wavelength of the buckling wave can be controlled by adjusting the elastic modulus,and then the wave number in a certain length can be controlled.(6)Although the two-way reversible transformation has been realized by shape memory polymer substrate-film structure,some progress has been made in the control of the buckling morphology,but further experimental and numerical studies are still needed.