Challenges in measuring fracture toughness of dental ceramics: SEPB method

Jodha, K.S.; Marocho, S.M. Salazar; Griggs, Jason A.

doi:10.1016/j.dental.2018.08.130

Cited by 1 publication

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“…Three methods for creating sharp cracks in beam specimens for determination of fracture toughness of advanced ceramics are introduced in ASTM C 1421 (ASTM, 2018), including the single‐edge pre‐cracked beam (SEPB) and the surface crack in flexure (SCF) methods. Using a bridge‐loading technique, the SEPB method extends precracks from either a shallow sawed notch or indentations (Jodha, Marocho, & Griggs, 2018; Quinn, Kübler, & Gettings, 1994). The geometry and residual deformation at the tip of the precrack influence the measurement, which should be treated with caution when calculating the fracture toughness value (Suresh, Ewart, Maden, Slaughter, & Nguyen, 1987).…”

Section: Introductionmentioning

confidence: 99%

Fracture toughness of zirconia with a nanometer size notch fabricated using focused ion beam milling

et al. 2020

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Objectives: Zirconia with 3 mol% yttria (3Y-TZP) has been used for dental crowns and bridges due to its excellent mechanical behavior. Performing fracture toughness testing on this nanograin material, however, can be a challenge. For reliable results, fracture toughness testing requires an extremely sharp notch in the test specimen that closely approximates a very sharp crack. This study was to investigate an alternative method to produce nanometer-sized notches, which are less than the average grain size of 3Y-TZP, during the preparation of single-edge V-notched beam specimens and report the resulting fracture toughness value. Methods: We present a method using focused ion beam (FIB) milling to fabricate nanometer-sized notches in 3Y-TZP. The notch tip is <100 nm wide, which is smaller than the grain size, and is consistent throughout the thickness of the specimen. Results: The FIB-notched specimens show a much reduced average fracture toughness of 5.64 ± 1.14 MPa√m compared to 8.90 ± 0.23 MPa√m for the specimens without FIB-notches. The FIB-milling did not appear to create any monoclinic phase prior to fracture toughness testing. Fractures originated at the FIB-notches, and the notch size can be readily identified post-mortem using a microscope. A considerable amount of tetragonal-to-monoclinic phase transformation was observed throughout the fracture surfaces. Significance: FIB milling provides an alternative method to fabricate nanometer-sized notches that are smaller than the grain size of tetragonal zirconia polycrystal. The fracture toughness determined using FIB-notches was $5.64 MPa√m, smaller than the specimens with V-notches fabricated using saw blades.

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Section: Introductionmentioning

confidence: 99%