Roughness of oxide glass sub-critical fracture surfaces. J. Am. Cer. Soc. 2018

Pallares G., Lechenault F., George M., Bouchaud E. Ottina C., Rountree C.L. and Ciccotti M., 2018.
Roughness of oxide glass sub-critical fracture surfaces. J. Am. Cer. Soc. 101:1279–1288.

An original setup combining a very stable loading stage, an atomic force microscope
and an environmental chamber, allows to obtain very stable subcritical fracture
propagation in oxide glasses under controlled environment, and subsequently
to finely characterize the nanometric roughness properties of the crack surfaces.
The analysis of the surface roughness is conducted both in terms of the classical
root mean square roughness to compare with the literature, and in terms of more
physically adequate indicators related to the self-affine nature of the fracture surfaces.
Due to the comparable nanometric scale of the surface roughness, the AFM
tip size and the instrumental noise, a special care is devoted to the statistical evaluation
of the metrologic properties. The roughness amplitude of several oxide
glasses was shown to decrease as a function of the stress intensity factor, to be
quite insensitive to the relative humidity and to increase with the degree of
heterogeneity of the glass. The results are discussed in terms of several modeling
arguments concerning the coupling between crack propagation, material’s heterogeneity,
crack tip plastic deformation and water diffusion at the crack tip. A synthetic
new model is presented combining the predictions of a model by
Wiederhorn et al (J Non-Cryst Solids, 353, 1582-1591, 2007) on the effect of the
material’s heterogeneity on the crack tip stresses with the self-affine nature of the
fracture surfaces.