Crack fronts and damage in glass at the nanometre scale

Abstract

Abstract. We have studied the low speed fracture regime for different glassy materials with variable but controlled length scales of heterogeneity in a carefully mastered surrounding atmosphere. By using optical and atomic force microscopy (AFM) techniques we tracked in real-time the crack tip propagation at the nanometer scale on a wide velocity range (10 −3 − 10 −12 m/s and below). The influence of the heterogeneities on this velocity is presented and discussed. Our experiments reveal also -for the first time -that the crack progresses through nucleation, growth and coalescence of nanometric damage cavities within the amorphous phase. This may explain the large fluctuations observed in the crack tip velocities for the smallest values. This behaviour is very similar to what is involved, at the micrometric scale, in ductile fracture. The only difference is very likely due to the related length scales (nanometric instead of micrometric). Consequences of such a nano-ductile fracture mode observed at a temperature far below the glass transition temperature, T g , in glass is finally discussed.

Nanoscale damage during fracture in silica glass

“…In other words, crack growth is intermittent and dominated by the accelerating phases corresponding to the cavity coalescence with the main CT. (iii) The nanocavitation process provides the dominant mechanism responsible for damage spreading within the process zone. Observations of damage cavities in amorphous Silica under stress corrosion are consistent to what was observed experimentally in Aluminosilicate glasses under stress corrosion (Célarié et al, 2003a, b;Marlière et al, 2003), and numerically during dynamic failure of amorphous Silica Rountree et al, 2002;Kalia et al, 2003). This indicates that the existence of this nanoductile mode is inherent to the amorphous structure and does not depend on the precise glass composition.…”

“…Observations of damage cavities in amorphous silica under stress corrosion are consistent with what was observed experimentally in aluminosilicate vitroceramics under stress corrosion by Célarié et al (2003a,b) and Marlière et al (2003), and numerically during dynamic failure of amorphous silica by Van Brutzel et al (2002), Rountree et al (2002) and Kalia et al (2003). This indicates that the origin of such a nanoscale damage mode is inherent to the amorphous structure and does not depend on the precise glass composition.…”

“…In other words, the crack front does not propagate regularly as commonly stated (Kelly et al, 1967;Lawn et al, 1980;Guin and Wiederhorn, 2004), but progresses through the growth and coalescence of cavities. This scenario is fully consistent with what was observed both experimentally in aluminosilicate vitroceramic under stress corrosion by Célarié et al (2003a,b) and Marlière et al (2003) (Figure 4(bottom)) and numerically in dynamic fracture of amorphous silica by Van Brutzel et al (2002), Rountree et al (2002) and Kalia et al (2003) (Figure 4(top)).…”

“…aluminosilicate vitroceramics (Célarié et al, 2003a, b;Marlière et al, 2003), nanophase materials Kalia et al, 2003), metallic alloys (Paun and Bouchaud, 2003), PMMA (Ravi-chandar and Yang, 1997) and polymers (Lapique et al, 2002). We argue that such mechanism is generic to crack propagation -the main difference resides in the typical lengthscales over which cavities are observed.…”

Thermal accumulation effect in three-dimensional recording by picosecond pulses

“…Recently, it was demonstrated that brittle materials can also demonstrate a ductile response before onset of crack formation at a specific crossover length of order 10 nm in glass. 5 Control of the local temperature and its distribution inside transparent materials at the focus allows one to tune a thermal stress for a desired application, e.g., a 3D dicing (a controlled cleaving) would require a controlled crack propagation, while the optical memory and waveguide recording would benefit from prevention of the crack formation by material softening/ melting.The aim of this work was to investigate the effect of thermal accumulation on 3D laser recording by 12 ps duration, 355 nm wavelength pulses at a high (80 MHz) repetition rate inside glass. The experimental results are compared with those of theoretical modeling.…”