Flexural strength testing has long been a staple technique for measuring
the uniaxial tensile strength of brittle materials such as ceramics
and glasses. Direct tension tests are less commonly used due
to the large test piece size, the high costs of specimen fabrication
and testing, and the difficulties of gripping without misalignments.
Both three- and four-point flexure configurations are used as shown
in Fig. 1. Four-point is preferred for most applications and it is
often qualified by an additional descriptor relating the fractional
size of the moment arm, a, to the outer span length, Lo.