双层薄膜与弹性梯度基底三层结构表面失稳分析

Surface instability of hard films adhered on soft substrate has always been a difficult problem for flexible electronic devices.Considering the shear stress between the bi-layer film and the elastic graded substrate,an analytical model of bi-layer film/elastic graded substrate is established.By using the displacement continuity of the interface,the analytical expressions of the critical strain and wavelength of the bi-layer film/elastic graded substrate are obtained.Then,through several examples,the validities of the proposed expressions are verified which are compared with those results obtained by the finite element analysis.At the same time,the influences of the geometric parameters of the bi-layer film and physical parameters of the elastic graded substrate on the buckling behavior are analyzed.The results in this paper show that decreasing the thickness of device layer or increasing the thickness of encapsulation layer can improve the stability of bilayer film/elastic graded substrate structure; if the substrate is relatively "soft" or the device layer is "hard",the shear force of the interface between the device layer and the substrate will be taken into account,which can prevent the resistance of the three-layer film/substrate structure from undergoing interface failure.Above all,the research will provide theoretical support for the fabrication of flexible electronic devices with hard film/elastic graded substrate structure.