Study On Flexibility Characterization And Fracture Influencing Factors Of Ultrathin Glass

With the increasing popularity of LCD,smart phone and tablet computer,display products are gradually becoming lighter and thinner.The electronic glass matching with them also needs to be lighter and thinner.Therefore,a kind of ultra-thin glass is developed.Ultrathin glass exhibits flexibility mechanics with thinning thickness,which has potential application value in flexible display,flexible battery and so on.Traditional mechanical testing methods of glass materials(such as three-point and four-point bending method,double-ring method,etc.)are based on the small deflection deformation of brittle glass materials,but these methods are not suitable for the characterization of mechanical properties of ultra-thin glass,especially the characterization methods of flexibility measurement of ultra-thin glass need to be solved urgently.In this paper,the method of measuring the critical curvature radius of ultra-thin glass based on the two-point bending method is proposed to characterize the flexibility of ultra-thin glass.The experimental device is designed and constructed.The bending image of ultra-thin glass is fitted.The influence of software fitting accuracy,loading rate and sample size on the flexibility test is analyzed.The fracture process and fragment morphology of ultra-thin glass were analyzed by means of high-speed camera.The influencing factors of fracture were explored from the aspects of glass variety,glass thickness,environmental humidity and cutting surface defects.(1)Based on the principle of two-point bending method,a method of measuring the flexibility of ultra-thin glass by critical curvature radius is proposed.A set of experimental equipment is designed and built.The critical curvature radius of ultra-thin glass is measured by fitting software,and the deformation of the middle part is the largest in the process of bending deformation,which is close to the circle.The measurement of critical curvature radius depends on the change of sample size and length.The optimum test parameters are as follows: loading rate is 5 mm/s,sample width is 50 mm,sample length is close to half of the bending circumference of specific thickness.(2)It is found that there are many kinds of fracture modes such as primary fracture,secondary fracture,multiple fracture and collision fracture in the process of bending fracture of ultra-thin glass.The origin point of fracture will affect the fracture morphology and the number of fragments.The larger the defect,the larger the fragmentation,and the smaller the defect,the smashing the fracture.(3)There are obvious differences in fracture toughness and impact resistance between ultra-thin low-alumina glass and ultra-thin high-alumina glass.The difference of curvature radius is only a few millimeters due to glass defects.The influence of glass defects conceals the difference of glass varieties.The thickness of ultra-thin low-alumina glass samples increases from 0.33 mm to 0.70 mm,the critical curvature radius increases linearly,and the relative standard deviation rate increases gradually.The critical curvature radius of ultra-thin low-aluminium glass samples with the same thickness is 1.2 times to 1.9 times of that of non-cutting bending samples,and the relative humidity is less than 50%,which has little influence on the measurement of the critical curvature radius.When the relative humidity is more than 90%,the critical curvature radius of ultra-thin glass increases by 1.4 times and the conductivity increases by 1.4 times.The brittleness of ultrathin glass is increased.