Vehicle windshields typically include a black decorative pattern around their periphery and other regions. Examination of field failed parts has shown that windshields often break from impacts in these decoration zones; often with the fracture initiating from the decoration material itself.
In this work, the effect of different glazing decoration materials on glass strength and laminate impact resistance was evaluated. The decoration materials investigated included traditional inorganic enamel frit, an organic ink, and a new enamel frit that is compatible with glass chemical strengthening.
Ring-on-Ring strength tests were conducted and showed that inorganic enamel frit reduces strength of glass by over 50% compared to undecorated glass, while organic inks do not adversely affect strength. Tests of a newly developed decoration frit material, compatible for chemical strengthening processes, showed strength levels that were on par with undecorated, unstrengthened glass.
Ball bearing impact tests were performed on conventional laminates (comprising two plies of annealed soda-lime glass (ASLG) bonded together with a resin inter-layer, typically of 0.8 mm poly-vinyl butyral (PVB)) incorporating the different decoration materials to quantify the effect of these materials and their relative location in the laminate stack on impact resistance. Results showed that laminates made with inorganic enamel decoration frit experienced a local decrease in impact performance when compared to undecorated laminates. Additionally, it was found that the surface on which the enamel frit was deposited, significantly affected impact durability. Laminates with enamel frit on Surface 3, significantly outperformed laminates that had enamel on Surfaces 2 or 4; with the Surface 2 location being the lowest performer with a degradation in impact resistance of ~50% relative to undecorated parts. Furthermore, it was found that laminates made with an organic ink decoration, do not suffer a reduction in impact performance relative to undecorated laminates.
Lastly, thin, light weight hybrid laminates (comprising of a standard annealed outer-ply with a thin, chemically strengthened inner-ply) that incorporate the newly developed decoration frit material, compatible with chemical strengthening processes, resulted in local impact resistance levels that exceeded the performance of the undecorated regions of standard laminates. Notably, these hybrid laminates exhibited local impact durability of more than double that of conventional laminates with inorganic enamel frits on surface 2.
