WINDOW SECURITY FILM INVESTIGATION BY OPTICAL TECHNIQUES

Knowing exact behaviour of the existing window security films when subjected to mechanical stresses is important for their further improvement and development. Security films are laminated to the glass windows by means of special adhesives and when breaking, the film keeps glass fragments together. In this paper we present an experimental study of standard glass samples retrofitted with security film. To reveal their properties two different tests were made. First, round specimens were impacted with dropping weights. The dynamic out-of-plane deformations were measured by fringe projection (moiré) technique. To extract the phase from the obtained fringe patterns, numerical algorithms based on Windowed Fourier Transform were used. Next, to learn more about unsticking resistance of the composite, the security film behaviour was studied via stretching parallel samples across a linear crack in the glass pad. To measure the 2D in-plane deformations a digital speckle-photography was applied. The local displacement fields were calculated by digital image correlation technique with sub-pixel resolution routine.