The use of laminated safety glass enables residual load-bearing capacity after fracture of the glass panes. The acting load is carried by the glass fragments (adhering to the interlayer) and the interlayer itself. The interlayer locally delaminates from the glass and experiences large strains. Hence, to numerically describe the post-fracture behaviour of laminated safety glass, nonlinear (strain dependent) viscoelastic material behaviour has to be taken into account for the interlayer. The most used laminated glass interlayer is polyvinylbutyral (PVB). For this, the viscoelastic material behaviour in the linear range (Prony parameters of the generalized Maxwell model and Time-Temperature Superposition Principle TTSP) and the linearity limits, which characterize the transition from linear viscoelastic to nonlinear viscoelastic material behaviour, are well described in literature. This paper investigates the viscoelastic Consideration of the nonlinear viscoelasticity of PVB through a Time-Strain Superposition behaviour at strain magnitudes exceeding the linearity limits. For this purpose, relaxation tests in uniaxial tensile mode are carried out on the interlayer material. During the tests a high deviation from linear viscoelastic behaviour is observed. The Schapery model, which extends the linear viscoelastic constitutive law with straindependent nonlinearity factors, is often used in literature to describe nonlinear viscoelastic material behaviour. The nonlinearity factors, which include a Time-Strain Superposition Principle (TSSP), were investigated to create a mastercurve.
Consideration of the nonlinear viscoelasticity of PVB through a Time-Strain Superposition
Company: Institute of Structural Mechanics and Design, TU Darmstadt
About the speaker:
Jens Schneider is a full professor for structural engineering at the Institute of Structural Mechanics and Design, TU Darmstadt, Germany. After his studies in civil engineering in Darmstadt and Coimbra, Portugal, Jens received his PhD from TU Darmstadt in 2001 in a topic about structural glass design and impact loading. From 2001-2005, Jens worked at the engineering office Schlaich, Bergermann and Partner where he was involved in the structural design of complex steel, glass and concrete structures. In 2006, Jens was appointed as an authorized sworn expert on glass structures, in 2007 to the position of a professor for structural engineering in Frankfurt. and in 2009 to his current position at TU Darmstadt, where Jens is currently Vice President for Transfer and International Affairs. Since 2011, Jens is also partner in his engineering office SGS GmbH in Heusenstamm in Frankfurt, Germany. Since 2015, Jens leads the European project group for the preparation of the new Eurocode 11 „Structural Glass“. From October 2023, he will serve as the new rector of TU Wien in Vienna, Austria.Jens is specialized in structural mechanics of glass & polymers, façade structures, structural design and synergetic, energy-efficient design of façades and buildings.