Study On Surface Buckling And Interface Adhesion Mechanics Of Typical Soft Material Structures

Soft material is a very important material in nature and industrial production.Its various structures are widely used in flexible electronics,soft robots,biomedicine and other emerging fields.The mechanical properties of surface interface of soft material structure directly affect the realization of touch control,sensing and other functions,which is of great importance.However,compared with hard materials,the surface instability and interface adhesion mechanics of soft material structures with broad application prospects are not fully studied,which seriously hinders the application development of soft material structures.In this thesis,experimental testing,finite element simulation and theoretical analysis are combined to study the surface interface mechanical behavior of typical soft material structures,focusing on the pressing instability of finite size thin-film substrate system,surface instability of spherical shell containing surface microstructure,and interface mechanics of structures containing soft material bonding layer.The research content is divided into the following three parts:(1)A finite size thin-film substrate system was prepared,and the buckling morphology of the system was obtained by designing experiments.The effects of different geometric factors,material factors and loading factors on the buckling behavior of the system were investigated by finite element simulation.The results show that when the elastic modulus of the base increases,the fold of the system becomes smaller until there is no obvious buckling morphology.When the thickness of the base increases,the morphologic change of the system buckling is not obvious,but the deformation degree of the base decreases obviously.When the radius of the indenter increases,the morphology changes of the system buckling are more obvious.When the radius of the indenter is small,there will be no fold at the boundary of the system.In the presence of a certain loading Angle,the film produces a relatively obvious large fold in the boundary region behind the indenter,and the part near the front edge of the indenter produces a slight circumferential uplift.(2)The buckling mechanism of the spherical shell containing surface microstructure was studied by combining experimental test,finite element simulation and theoretical analysis.The results show that the larger the thickness of the spherical shell,the more stable the structure of the spherical shell,the more stable the mechanical response to compression,and the more stable the second type of buckling morphology.The larger the outer radius of the shell,the smaller the mechanical response of the shell.The spherical shell with protrusion is analyzed,and it is found that the existence of multiple loops of protrusion leads to multiple snap-throughs.The first snap-through of the spherical shell with protrusion is caused by the configuration change and the local buckling caused by the first loops of protrusion.The larger the radius of the protrusion,the more obvious the mechanical effect at the snap-through.The Angle of the protrusion results in a different contact area between the protrusion and the spherical shell,which affects the mechanical reaction of the spherical shell.The number of protrusions has little effect on the mechanical response of the spherical shell,but has great effect on the morphology evolution of the spherical shell.At the same time,the mechanical response and buckling mechanism of spherical shells containing continuous surface microstructure such as fringes are similar to those of spherical shells.(3)Based on the bonding region model,the strength analysis of the butt structure of the hydrogel bonding layer was carried out,focusing on the influence of geometric factors and material factors of the hydrogel bonding layer on the strength of the bonding structure.The results show that the proposed butt model can well study the mechanical behavior of the butt structure with the hydrogel bonding layer at different fracture angles.In order to improve the strength of the adhesive structure,the appropriate thickness and weight ratio of the hydrogel adhesive layer were designed in clinical application.In engineering practice,the butt structure will inevitably offset,so it is necessary to consider and select a reasonable bonding layer in advance.Due to the Mullins effect of the hydrogel bonding layer,the structural strength of the bond will be significantly reduced.