Scope:

The ASTM C1211 standard determines the flexural strength of advanced ceramic materials under increased temperatures and ambient environmental conditions at a minimal, fairly fast testing rate. Rectangular specimens of the defined cross-section are loaded either in four-point or three-point configuration at a high temperature in a prescribed specimen fixture combination as per ASTM C1211. This test method is intended to be used with ceramics whose flexural strength is at least 50 MPa or greater. This test method may also be used for material development, quality control, characterization, and design data generation purposes.  

Test Procedure:

In ASTM C1211, the specimens are tested on their respective fixtures in defined testing configurations as specified by the test. So specimen A is fixed on a four or three-point A fixture, specimen B on B fixtures, and specimen C on C fixtures. The specimen has an equal amount of overhang beyond the outer bearings and is centered beneath the axis of the applied load. The load is applied to the fixture at a straight angle. The standard specifies crosshead speeds for various test settings. To identify tensile and compression forces, the specimen is marked at the sites of load. These markers will assist in post-fracture investigation and interpretation. At the sample break, the test is stopped and the brake force is recorded. 

Specimen Size : 

As per ASTM C1211, cross-sectional dimensional tolerances are ± 0.05 for specimen A and ± 0.13 mm for specimens B and C. The four long edges of each specimen shall be chamfered uniformly at 45°, at a distance of 0.12  ± 0.03 mm. 

Data:

In ASTM C1211, the flexural strength of advanced ceramics is reported in the SI units and is considered standard.

• The standard formula for the strength of a beam in four-point flexure is as follows:

S=3 PL/4bd²

• The standard formula for the strength of a beam in three-point flexure is as follows:

S = 3 PL/2bd²

where,

P = break force.

L = outer (support) span

b = specimen width

D = specimen thickness

Conclusion:

The ASTM C1211 standard determines the flexural strength of advanced ceramic materials under increased temperatures and ambient environmental conditions at a minimal, fairly fast testing rate.