Study On Buckling Behaviours Of The Flexible Film Substrate Structure

The flexible film substrate structure has the advantages of light weight,large deformation,portability,etc.,and has broad application prospects in various frontier fields such as flexible thermal protection systems,flexible electronics,and biomedical engineering.Compared with the traditional rigid structure,the flexible film substrate structure is more likely to lose its stability under the action of external loads,and then generate a large range of buckling waves,thereby changing the structure of the structure and affecting the mechanical or physical properties.In this paper,a combination of theory,experiment and simulation is used to focus on the buckling behavior of flexible film substrate structure.It has important theoretical and engineering significance for design and application.Firstly,the critical prediction formulas for buckling and delamination of the flexible film substrate structure are obtained by energy method,and parametric analysis and comparison were carried out by experimental and numerical analysis methods.In the experiment,a uniaxial compression experiment is conducted by preparing a flexible film substrate structure with high interfacial bonding strength.With VIC-3D non-contact digital photogrammetry,the morphology and instability characteristic parameters of surface wrinkles and delaminations are accurately obtained.By establishing a "pre-stretch-compression" model,the effects of material parameters such as elastic modulus and Poisson’s ratio of thin film and substrate on the overall instability are obtained.The length of prefabricating local delaminations influences the deformation evolution law from buckling to delamination,which provides a basis for controlling buckling and deformation of the structure.Secondly,taking the flexible thermal protection system(TPS)as the research object,the lateral deformation of the flat flexible TPS under the surface pressure is is only 0.01%.It is difficult to break through the bottleneck of fracture strength by modifying the design of materials.According to the "over-shrinkage" feature of wrinkles,a structural design proposal for flexible TPS incorporating corrugated surface design is proposed,aiming to achieve an efficient internal wall that resists intense heat,achieves high efficiency normal carrying and large lateral deformation.Through simulation analysis,it is verified that the flexible TPS with corrugated surface design can enhance the lateral deformation ability on the basis of ensuring normal load by increasing the waviness amplitude and decreasing the wavelength.Finally,three-dimensional heat transfer models are built for the flexible TPS with different configurations.Through the complete thermal-mechanical coupling simulation analysis,it is proved that the thermal protection effect of the corrugated flexible TPS is better than that of the flat TPS.The average thermal conductivity is tested to evaluate the thermal protection effect of the laminated structure relative to a single thermal insulation material.By preparing a flat flexible TPS and TPS with a curvature of the overall structure,a high-temperature heat flow experiment is conducted to compare the temperature rise of the cold face after the same time.It proves that the corrugated flexible TPS can prevent heat better than flat TPS,which is consistent with simulation results.