Cracking and residual stress in hybrid coatings on float glass

Observations with respect to the cracking of hybrid organic–inorganic coatings applied on float glass are reported. The coatings were deposited using a spin coating technique. The films showed cracks above a critical thickness and delaminated largely from the substrate. A relationship between the crack spacing and the film thickness is reported, and described by a model relating multiple cracking and crack spacing to the coating thickness for elastic relaxation. Thicker films had a higher initial stress associated with a higher number of cracks. The residual stress was calculated using the bending of the delaminated coating fragments and was proportional to the squared coating thickness. The results on the residual stress and the critical thickness allowed the fracture toughness of the coatings to be determined