Experimental study on the dynamic behaviour of glass fitted with safety window film with a small-scale drop weight set-up

• A widely instrumented small-scale drop weight set-up has been designed.
• Compared with current standardized test methods it provides much more information.
• Glass specimens fitted with window safety film are subjected to hard & soft impact.
• Elastic response is very reproducible.
• Film thickness has a negligible influence in case of a hard impact.

Retrofitting existing windows with a safety window film, to improve impact resistance, has been increasing along with the awareness of potential attacks on strategic buildings. However, current classification of glass panels is based solely on discrete outcomes of standardised tests without any instrumentation. In this paper, a versatile small-scale drop weight test set-up is conceived which is widely instrumented (accelerometer, force sensor, displacement sensor, high-speed visual observation) in order to gain more insight in the mechanical impact response of glass fitted with a safety window film. The elastic response, determined by the much higher stiffness of the glass, was very reproducible. The impacted surface (glass vs. film side) had a large influence, whereas the tensioned surface and laminated surface (air vs. tin side), do not. The film thickness only had an influence when the film was tested separately (without glass substrate) or in case of a soft impact of glass.