1.1 These test methods cover the determination of flexural
properties of unreinforced and reinforced plastics, including
high-modulus composites and electrical insulating materials in
the form of rectangular bars molded directly or cut from sheets,
plates, or molded shapes. These test methods are generally
applicable to both rigid and semigid materials. However
flexural strength cannot be determined for those materials that
do not break or that do not fail in the outer surface of the test
specimen within the 5.0 % strain limit of these test methods.
These test methods utilize a thee-point loading system applied
to a simply supported beam. A four-point loading system
method can be found in Test Method D 6272. .
1.1.1 Procedure A designed principally for materials that
break at comparatively small deflections.
1.1.2 Procedure B, designed paricularly for those materials
that undergo large deflections during testing.
3 Procedure A shall be used for measurement of flexural
properties, paricularly flexural modulus, unless the material
specification states otherwise. Procedure B may be used for
measurement of flexural strength only. Tangent modulus data
obtained by Procedure A tends to exhibit lower standard
deviations than comparable data obtained by means of Procedure
B.