Glass Creep of Unsupported Lites in Laminated Glass

Laminated glass is being used in applications because of its many value add characteristics. As the use of laminate glass increases, architects, designers and installers push the envelope on how it is used. One structurally glazed application may not always have the full laminate glass thickness supported along its bottom edge. If this installation style is required, the question of how much vertical slip or “creep” the unsupported glass layer (ply) would exhibit is frequently asked. A test method to assess creep performance in laminates has been created since no international standard exists and in-situ data is difficult to obtain. Laminated glass specimens having a size which is safe and easy to handle are subjected to a test method which allows the front glass layer (ply) to remain supported only by the interlayer. The interlayer creep test method, and results of subsequent testing of various laminated architectural glass products are presented in this report. Laminated specimens were subjected to high temperatures over an extended period of time and the resulting change in glass alignment is reported, thus providing a measure of creep which has occurred under test conditions. The test method development, creation of test fixtures, evaluation of various interlayers having common thicknesses and the effect of glass thickness on creep was examined. Test results demonstrated that conventional interlayers have some amount of creep over the test duration while stiff PVB interlayers do not exhibit creep under the conditions tested.

Julia Schimmelpenningh

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