2.2. Test specimens
Rectangular beams (3 mm4 mm cross-section) Vnotched in two stages were used as test specimens [7].
The package of 2–6 specimens were glued onto a ceramic plate and then V-notched.
Two additional specimens were fixed on both sides of the package for its protection from the edge effects due to notching.
A preliminary notch 0.8 mm deep (specimens for fourpoint flexure) or 1.6 mm deep (specimens for three-point flexure) was cut in the package by a 150–300 mm thick diamond disk.
At the next stage, the V-notch was manually (convenient for comparatively ‘‘soft’’ ceramics) or mechanically (necessary for ‘‘hard’’ ceramics) polished-out after filling the preliminary notch with a diamond paste of grain sizes ranging from 2 to 7 mm and a razor blade 150–300 mm thick.
In the case of manual polishing-out, the walls of the preliminary notch (1.6 mm deep) served as the razor blade guides.