Fracture of glasses

We noted in passing that when the tensile stress applied on a glass 

Griffith flaws which have very low depths. They are characterized using decoration techniques. Griffith s equation can be written alternatively as. 

It may be of interest to note here that the failure of glass exhibits a dependence on time. For example when a constant stress of the order of magnitude of K/c is applied, the time-to-failure varies inversely as the applied stress. On the contrary if the applied stress is continuously increased such as to keep a constant strain rate, stress-to-failure varies directly as strain rate. These are manifestations of delayed failure which is due to the phenomenon of fatigue. Observations made under constant stress measures the static fatigue while the observations under constant strain rate conditions measure dynamic fatigue. The difference in 

Hilling and Charles (1965) analysed sub-critical crack velocity, v under general conditions including the effect of chemical environment which can give rise to surface flaws. The velocity, v, of crack propagation is given by. 

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Bailey, J. E., Ellis, B., Howarth, L. G. Oldfield, C. W. B. (1991). The fracture of glass-ionomer cements. Conference on the Fractography of Glasses and Ceramics II, New York State College of Ceramics, Alfred University, New York, July 1990. American Ceramic Society. 

Freiman SW, Wiederhom SM, Mecholsky Jr. JJ. Environmentally enhanced fracture of glass a historical perspective. Journal of the American Ceramic Society 2009 92(7) 1371-1382. 

Zha Zhang, K., Berglund, A. Deformation and fracture of glass bead/CTBN-rubber/epoxy composites. Polym. Eng. Sci. 33 (1993) 100-107. 

OOLee Lee, J., Yee, A. F. Fracture of glass bead/epoxy composites on micro-mechanical deformations. Polymer 41 (2000) 8363-8373. 

S. J. Bennison, A. Jagota and C. A. Smith, Fracture of Glass/Poly(vinyl butyral) (Butacite ) Laminates in Biaxial Flexure, 7. Am. Ceram. Soc. 82, 1761-1770(1999). 

Kinloch AJ, Masania K, Taylor AC, Sprenger S, Egan D (2007) The fracture of glass-fibre-reinforced epoxy composites using nanoparticle-modified matrices. J Mater Sci 43(3) 1151-1154... 

B. R. Lawn and T. R. Wilshaw, Fracture of Brittle Solids, 168-172, Cambridge University Press, Cambridge, England, 1972. www.ceramics.org/lJAGS The Fracture of Glass 103... 

One peculiar feature associated with the fracture of glasses is that it always originates on the surface. This means that the near-surface layers have the most favorable conditions for the formation and development of defects resulting in microcracks. Numerous studies indicated that the ranoval of the near-surface layers leads to a significant increase in the strength of glass. 

The above theory implies that if the surface energy term y is reduced, then 9pr will also be reduced. This led Orwan [80] to suggest that delayed fracture of glass occurs by adsorption of environmental species which lowers the surface energy, and hence the stress required to cause fracture. The same principles were later adopted to account for the SCC of metals. If environmental... 

Menclk, J. Strength and Fracture of Glass and Ceramics Elsevier Amsterdam, The Netherlands, 1992 pp 17-180. 

Lee, J. and A. F. Yee, Inorganic particle tonghening I Micro-mechanical deformations in the fracture of glass bead filled epoxies. Polymer, 2001a. 42(2) 577—588. 

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