The effect of PVD coatings on the ring-on-ring flexural strength of soda lime silica float glass was studied. A 70% increase from 280±8 to 478±10 MPa was observed on the air-side of the glass after applying a multilayer low emissivity coating of 100 nm total thickness. A similar, but less pronounced effect could be obtained with a TiO2 single layer of 50nm. At the same time, for both coatings, the Weibull modulus was found to approximately double. Results are interpreted on the basis of two assumptions: initial defects on the glass surface are covered by the coating, and their growth is prevented due to the protective function of the coating, especially as a humidity barrier. Both assumptions were confirmed by atomic force microscopy and micro-mechanical analyses. This barrier function leads to significantly improved resistance to long term fatigue and stress corrosion, respectively.
