///PhD Defense: Characterization of Laminated Safety Glass Interlayers – Thermorheology, Crystallinity and Viscoelasticity by Miriam Schuster
Laminated safety glass enables the safe construction of transparent structures. The mechanical behaviour depends on the polymeric interlayer both in the intact and in the post fracture state. In the present work, the mechanical behaviour of ethylene vinyl acetate based (EVA) and ionoplastic interlayers is investigated for the intact laminated safety glass condition. The mechanical behaviour of the interlayer in the fractured laminated safety glass is carried out on polyvinyl butyral- based (PVB) interlayers.
The interlayer creates a shear coupling between the glass plies in intact laminated safety glass, which varies, among other things, on the temperature- and load duration-dependent shear modulus of the interlayer and is considered by means of Prony series and time- temperature-superposition principles. Since Prony series and time-temperature shifts have so far predominantly been determined for PVB interlayers, the structure of EVA and ionoplastic interlayers is investigated in more detail in this work. Using X-ray diffraction, differential scanning calorimetry and Dynamic-Mechanical-Thermal-Analysis, a semicrystalline structure is detected and analyzed for different temperature rates and physical ages. The displacement factors required for mastercurve generation are divided into a purely temperature-dependent and a purely degree-of-crystallization-dependent part, so that the material behaviour can be predicted for any temperature and degree of crystallization combination.
In the fractured state, large deformations occur in the interlayer, so that the loading level is also taken into account in the mechanical characterization of the interlayer. First, the temperature and frequency (time) dependent linearity limits of two different PVB interlayers are determined in dynamic-mechanical-thermal-analyses. The nonlinear viscoelastic material behaviour is investigated with tensile relaxation tests at different temperatures and strain levels and the Schapery model is investigated to represent the nonlinear viscoelastic material behaviour.
Defense date: 21.01.2022