Experimental investigations on the creep behaviour of PVB under different temperatures and humidity conditions

摘要

The use of structural glass applications with requirements on post-fracture performance has so far only been possible under consideration of large-scale tests. The development of a design concept for fractured laminated glass is the subject of current research in structural glass engineering. This requires material models for the respected components (glass and polymer interlayer). Since moisture can reach the polymer interlayer in the fractured state via the cracks in the glass, investigations on the mechanical behaviour of the interlayer at different air humidity levels are necessary. In order to obtain the first systematically recorded parameters for the material behaviour of the most common polymeric interlayer used in laminated glass, standard Polyvinylbutyral (PVB), a test set up was developed for carrying out creep tests at different levels of load, humidity and temperatures. Subsequently, tests were conducted which were evaluated with the help of Digital Image Correlation. The results show that the stiffness of the interlayer decreases significantly with increasing relative humidity and temperature. Based on the data obtained, material models can be developed which take into account the influence of the interlayer moisture on the post fracture performance of laminated glass. Analogously to the time temperature superposition principle it can be shown, that the application of a time humidity superposition principle is possible and standard PVB is approximately a moisture rheological simple material.