|These test methods employ a three point loading system applied
to a simply supported beam. And can be used to determine the
flexural properties of reinforced and unreinforced plastics,
including high-modulus composites and electrical insulating
materials. The test specimens are in the form of rectangular
bars which may be molded in that shape specifically for testing
purposes, or be cut from molded shapes, plates, or sheets. The
ASTM D 790 specifications apply to both rigid and semi-rigid
materials. Flexural strength however, cannot be determined for
materials that do not break or do not fail in the outer surface
of the test specimen within the 5.0 % strain limit of these test
methods. In these test methods, both Procedures A and B, a
rectangular specimen rests upon two supports and is loaded
midway between the supports. The test specimen is deflected
until rupture occurs in the outer surface of the specimen or
until a maximum strain of 5.0% is reached, whichever happens
first. The standard support span-to-d