Fracture Toughness And Fractal Analysis Of Ceramic Benchmark Material

Objectives: To determine the relationship between fracture toughness (K_Ic) and the fractal dimensional increment (D*) of the fracture surface calculated using a new and unbiased technique on a benchmark material (silica glass).
Methods: The K_Ic of rectangular beams of pure silica glass (Viosil SX, n=6) was evaluated by the surface crack in flexure (SCF) method according to the ASTM C1421 with a Knoop indentation followed by four-point flexure in deionized water. Fracture surfaces were also analyzed using fractal analysis. The critical flaw sizes were measured using a scanning electron microscope (Supra 40, Zeiss, USA). Epoxy replicas of the mirror region of the fracture surfaces were prepared. The replicas were analyzed using the traditional Slit-Island Richardson technique to calculate D*.
Results: The mean ± standard deviation K_Ic and D* silica glass were 0.93 ± 0.20 MPa●m^1/2 and 0.10 ± 0.04, respectively.
Conclusions: The calculated K_Ic value silica glass agrees closely with previously reported values for that material (Wiederhorn). Linear models relating K_Ic and the square-root of D* for previously investigated materials fit well to the data for silica glass (R²=0.96). This validated method may now be used to estimate the fracture toughness of dental prostheses and implants that have failed clinically.