Analysis on the Mechanical Behavior of Flexible Screens

Abstract

Recently, flexible organic light-emitting devices (OLEDs) have become more and more popular. However, the force distribution and deformation are very complex during the bending process, and it is difficult to analyze the stress and strain by theoretical analysis and direct experiment. In this paper, finite element analysis of the bending model for the flexible screen was performed. For common U-shaped bending, it was shown that the maximum Mises stress increases rapidly as the bending radius decreases, and the redistribution of the tensile zone and the compression zone should be the key to the layer material selection. The results were verified by an imaging experiment. Further, a water-drop-shaped bending mode was analyzed to reduce the risk of structure failure.

Experimental study on the constitutive model of optically clear adhesive films under rapid loading

“…Similar to the FEM results based on the isotropy method shown in Figure 17, there are significant deviations from the test data, and the built-in hyperelastic one cannot represent the correct out-plane shear mechanical properties. Although a hyperelastic constitutive model of OCA can be directly established only by uniaxial tensile tests, 14,16 certain accuracy may be lost in analyzing the bending process dominated by shear deformation. 7,10,45 Before bending stress analysis, pure shear or simple shear stress simulation should be carefully carried out to verify the constitutive model.…”

“…However, in fact, OCA is a viscoelastic material whose mechanical behaviors are time-dependent and loading rate-dependent. 1,2,[14][15][16] Due to the viscoelasticity, the comprehensive constitutive relationships of OCA can be distinguished into three parts: (i) the stress-strain relationship under rapid loading; (ii) the creep constitutive relationship under constant loading; and (iii) the stress-strain relationship under rapid unloading, as illustrated in Figure 1. This study focuses on the constitutive relationship under rapid loading.…”

“…In terms of the viscoelastic constitutive model of OCA, the generalized Maxwell models represented by the Prony series are often adopted. 11,[13][14][15][16] In recent work, Hsu et al 14 carried out uniaxial stress relaxation tests of OCA at different strain levels, and they determined a four-pair Prony series model to characterize the rate dependence of uniaxial tension, which lacked the verification of anisotropic viscoelasticity. Wang et al 15 and Niu et al 16 adopted simple shear stress relaxation tests to characterize the viscoelasticity of OCA, without demonstrating the loading rate-dependent behavior.…”

“…11,[13][14][15][16] In recent work, Hsu et al 14 carried out uniaxial stress relaxation tests of OCA at different strain levels, and they determined a four-pair Prony series model to characterize the rate dependence of uniaxial tension, which lacked the verification of anisotropic viscoelasticity. Wang et al 15 and Niu et al 16 adopted simple shear stress relaxation tests to characterize the viscoelasticity of OCA, without demonstrating the loading rate-dependent behavior. In these existing studies, the effect of viscoelasticity on loading characteristics was simplified by only one deformation mode, and the anisotropic viscoelasticity in the material's principal axes has been not investigated.…”

Research of aging test on high Tg colorless polyimide

“…We designed a series of aging test experiments to investigate the influence of high temperature and atmosphere on the Tr% of CPI films with structure of Glass/SiO 2 /CPI/SiO 2 , as shown in Figure 1a. Samples 10, 12, and 14 underwent aging at temperatures of 430, 450, and 470°C for 120 min in an N 2 atmosphere, respectively 8–11 . Sample 8 did not undergo aging, while sample 11 was aged at 450°C for 120 min in an air atmosphere.…”