Surface structural relaxation of silica glass: a possible mechanism of mechanical fatigue

Effect of Stress Gradient at the Vicinity of A Crack Tip on Ionic Diffusion in Silicate Glasses: An Afm Study

“…These authors showed indeed that the uptake of water in the structure of the studied silica glass causes a structural relaxation occurring in the near-surface region leading to an initial rapid decrease in the sodium diffusivity followed by a slow increase with the water content. Our results strengthen the theoretical concept of a near-surface structural relaxation [43]. We believe that the stress-gradient present at the vicinity of the crack tip is of major importance to enable the glass network to undergo a structural relaxation causing long-range structural changes, leading to modifications of bonding angles and distances and consequently enhancing mobility of alkali cations.…”

“…Furthermore these studies reveal that surface crystallization of oxide glasses [18] or observation of nm-scale structures on air-exposed fractured surfaces of soda-lime silica [46] stems very likely from the ionic migration due to residual stress gradient and the related process of interdiffusion with H + /H 3 O + ions. Our results strengthen the theoretical concept of a near-surface structural relaxation [43]. We believe that the stress-gradient present at the vicinity of the crack tip is of major importance to enable the glass network to undergo a structural relaxation causing long-range structural changes, leading to modifications of bonding angles and distances and consequently enhancing mobility of alkali cations.…”

Anomalous Enthalpy Relaxation in Vitreous Silica

“…The size effect was also found for the tensile strength of glass fibers (Lund and Yue, 2010). The surface structural relaxation of vitreous silica may be the mechanism of the mechanical fatigue (Tomozawa and Hepburn, 2004). However, the enthalpy relaxation of HQ glasses during annealing is a bulk effect, not a surface effect and this is confirmed by the matching between experimental observations and physical modeling of the bulk relaxation (Hornbøll et al, 2010).…”

Determining the mechanism controlling glass fibre strength loss during thermal recycling of waste composites

“…The mechanisms responsible for the loss in fibre strength have been much-debated and fully a satisfactory conclusion has yet to be drawn. Two main mechanisms have been investigated over the years: (1) thermally-activated changes to the anisotropic silica network structure initially induced by the high drawing stress during fibre manufacture [16][17][18][19], and (2) thermally-induced diffusion of water into the fibre surface leading to increased surface area and larger micropores as indicated through surface area measurements and fractography [15,[20][21][22]. Additionally, in a reverse study it was shown recently that glass fibres can be strengthened beyond their as-received strength via generation of additional surface compressive residual stresses during exposure to elevated temperatures [23].…”