Can i use a specimen with dimension of 3x3x25 mm3 (thicknessxWidthxLength) for three point bending test for flexural strength. The material of specimen is ceramic (YBCO superconductor).
Regarding the length, usually 30 or 40mm between supports in a three-point bending, therefore the total length should be >35mm or >45mm respectively. Keep in mind the tolerances and also that a four-point flexure is usually preferred, since a large amount of material is exposed to the maximum stress . Anyways, the cross section of the samples for 3-pont or 4-point bending, according to ISO 14704 test standard, 3mm (thickness) X 4mm (width). The cross-sectional tolerances shall be ± 0,2 mm. An additional consideration is the temperature. Are you testing at room temperature?