Contact Damage on Glass Surfaces Caused by Impact and Abrasion

James R. Varner, William C. La Course, Jacqueline Rolf, and Ufuk Senturk

Contact damage on glass surfaces is responsible for
loss of strength and loss of optical quality of flat glass
in service. Impact, even with small particles, can
produce cracks that cause significant drops in
strength and noticeable light scattering. Abrasion
leaves visible scratches and may leave strength-limiting
cracks as well. Producers and processors of
glass need to understand how contact damage is
produced, what effects it has on strength and optical
quality, and what can be done to prevent or minimize
such damage. This paper presents an introduction
to the topic of contact damage on glass surfaces.
The different crack systems produced by impact with
blunt and sharp objects are discussed and illustrated
with examples. Abrasion damage is related to impact
damage, but it has its own unique features, which
are also discussed. The role of indentation testing
in investigating contact damage is presented. Finally,
the influence of factors that influence contact
damage, including surface compressive stresses,
removal of alkali ions from the surface, and glass
structure, are discussed.

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