In situ observation and analysis of multiple cracking phenomena in thin glass layers deposited on polymer films

The multiple cracking phenomena in thin SiOx films deposited on 12 mu m-thi ck polyethylene terephthalate (PET) substrates during the tensile test are investigated. Thicknesses of SiOx films ranged from 43 to 320 nm. The multi ple cracking progress is observed in situ by optical microscopy and from wh ich the crack density in SiOx films is measured. The predicted crack densit y by the shear lag analysis including residual strains, explains reasonably well the experimental results. The critical energy release rate, G(c), for the first film cracking is also evaluated from simple energy balance argum ents. Although it depends on the analytical model, G(c) is estimated to be a constant value of about 1.0 J/m(2) regardless of the thickness.