> Investigating the strength of cast glass
Cast glass, glass strength, fractography, structural glass, glass properties.
2018 - ongoing
T. Bristogianni, Dr. F. Oikonomopoulou
T. Bristogianni, Dr. F. Oikonomopoulou, Dr. F. Veer, Prof. Dr. M. Overend
Cast glass has great potential for diverse load-bearing, architectural applications; through casting, volumetric glass components can be made that take full advantage of glass’s stated compressive strength. However, the lack of engineering, production and quality control standards for cast glass and the intertwined ambiguities over its mechanical properties -particularly due to the variety in chemical compositions and the lack of understanding of the influence of flaws occurring in the glass bulk- act as an impediment to its wide-spread application. Addressing the above uncertainties, TU Delft has initiated the research on the mechanical properties of cast glass, investigating how these properties are interrelated to the chemical composition and the inherited -during the casting process- defects at the surface and glass mesostructure. Of particular interest is the understanding of the amount of defects a cast glass component can tolerate in its bulk, while retaining reliable mechanical properties that allow its structural use in building applications. In that direction, the recycling of contaminated waste glasses can be enabled, providing a solution to currently non-recycled glass from the discarding of e.g. coated/enamelled soda-lime float, borosilicate and aluminosilicate glass products.
Various methods are employed in order to determine the material properties of cast glass. These include chemical composition analyses of the glass source and contaminants by X-Ray Fluorescence spectrometry (XRF), prototype casting at the TU Glasslab facilities, glass defect identification with digital microscopy and qualitative stress analysis using cross polarized light. The Impulse Excitation Technique (IET) is employed to measure the Young’s modulus and internal friction of the different glasses. Differential Scanning Calorimetry (DSC) is applied to study the glass transition and crystallization range of the various tested glasses. Four-point bending experiments accompanied by Digital Image Correlation (DIC), and splitting experiments are conducted, to define the flexural strength, Young’s modulus and fracture resistance of the specimens. Fractographic analysis with the help of digital microscopy pinpoints the most critical defects per glass category. The results highlight the versatile role of defects in determining the glass strength, advise on the correct engineering and application of the different cast glass qualities, and inform the quality control process.
T. Bristogianni, F. Oikonomopoulou, F. Veer, R. Nijsse, 2021. Evaluation of the fracture resistance of cast glass. International Journal of Structural Glass and Advanced Materials Research.
T. Bristogianni, F. Oikonomopoulou, F. Veer, 2021. On the flexural strength and stiffness of cast glass. Journal of Glass Structures & Engineering.
T. Bristogianni, F. Oikonomopoulou, R. Yu, F. Veer, R. Nijsse, 2020. Investigating the flexural strength of recycled cast glass. Journal of Glass Structures & Engineering
Best paper 2020 Award by the Editors-in-Chief of Glass Structure & Engineering Journal