Regulation Of Four-point Buckling Composite Sandwich Plates Morphology Of SMP Film/Substrate

Shape Memory polymer(SMP)is a new kind of smart material.This material can be restored to the initial shape in the end through a series of internal changes by external stimuli(such as heating,lighting,electricity,magnetism and so on)after the deformation.Due to its excellent properties such as low density,low price and good biocompatibility,SMP materials are widely used in biological medicine,clothing manufacturing,electronic instruments,aerospace and other fields.But the inherent defects of SMP material also limit its development and application in other fields.In order to improve the mechanical properties of SMP materials,domestic and foreign researchers have paid more attention to the research on the composites and composite structures of shape memory polymers in recent years.The hard film-soft base system is a kind of composite structure of soft materials which is widely used.The physical mechanism and geometrical morphology of the instability are complex in many aspects,such as 3d surface morphology,large deformation,geometrical and material nonlinearity.However,the buckling process of the general hard film-soft base system is unidirectional.It means that it is difficult for the structure to recover to the stable state before buckling after buckling under external load.In this paper,a sandwich plate of SMP hard film-soft base composite structure was designed based on the memory performance of SMP and the buckling characteristics of the hard film-soft base system,in order to accurately control the buckling behavior of the hard film-soft base system and realize its bidirectional deformation function.The structure was composed of three kind of epoxy resin-base shape memory polymer materials with different glass transition temperatures.By means of thermodynamic experiments and numerical simulation,the buckling morphology of SMP hard film-soft base sandwich plate under four-point bending load is studied in this paper.The main research contents are as follows:(1)Several SMP samples with different material parameters were prepared by using epoxy resin and curing agent as raw materials in the laboratory,and the SMP hard film/soft base composite structure sandwich plate specimens were made by using these samples;(2)Through previous literature reading,it was found that the factors affecting the surface buckling morphology of SMP film/substrate structure contained the thickness of films and substrates,temperature and preloading size,etc;(3)Based on this,then the thermodynamic experiments were carried out to test the four-point bending loading and recovery of these specimens at high temperatures.The complete shape memory process from bending buckling to shape recovery and the two-way transition from instability to recovery of the hard film-soft base system were successfully realized;(4)Then,the thermodynamic constitutive model and viscoelastic theory of SMP are introduced.On this basis,the finite element model was established by ABAQUS to simulate the whole experimental processes;(5)Finally,by comparing the simulation results with the experimental results,the eftects of temperature,load,thickness of film and substrate on the buckling norphology and the bending curvature of the substrate was obtained.The results provide a basis for the further study of the film/base structure buckling morphologies under quantitative control.The results show that the buckling norphology of the hard film/soft base can be accurately controlled by adjusting the temperature,load,thickness ot film and base.