On the flexural strength and stiffness of cast glass

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Abstract

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, this
work studies a total of 64 silicate-based glass specimens,
prepared in 20 * 30 * 350mm beam size, either
by kiln-casting at relatively low forming temperatures
(970–1120 ◦C), or by modification of industrially produced
glass. For the kiln-casting of the specimens, pure
and contaminated recycled cullet are used, either individually
or in combination (composite glasses). The
defects introduced in the glass specimens during the
casting process are identified with digital microscopy
and qualitative stress analysis using cross polarized
light, and are categorized as stress-inducing, strength reducing
or harmless. The Impulse Excitation Technique
is employed to measure the Young’s modulus and internal friction of the different glasses. Differential
Scanning Calorimetry is used on a selection of
glasses, to investigate changes in the glass transition
range and fictive temperature of the kiln-cast glasses
due to the slower cooling and prolonged annealing.
The four-point bending experiments are shedding light
upon the flexural strength and stiffness of the different
glasses, while the fractographic analysis pinpoints
the most critical defects per glass category. The experiments
show the flexural strength of cast glass ranging
between 30–73MPa, according to the level of contamination
and the chemical composition. The measured E
moduli by both methods are in close agreement, ranging
between 60–79GPa. The comparison of the flexural
strength with prior testing of cast glass involving
shorter span fixtures showed a decreasing strength
with increasing size for the contaminated specimens,
but similar strengths for pure compositions. The results
highlight the versatile role of defects in determining the
glass strength and the complexity that arises in creating
statistical prediction models and performing quality
control.
Original languageEnglish
Pages (from-to)147-194
Number of pages48
JournalGlass Structures and Engineering
Volume6
Issue number2
DOIs
Publication statusPublished - 2021

Keywords

  • Cast glass
  • Glass contamination
  • Glass defects
  • Glass flexural strength
  • Mechanical properties of glass
  • Recycling of glass waste

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