This test method determines the flexural properties (including strength, stiffness, and load/deflection behavior) of polymer matrix composite materials under the conditions defined. Procedure A is used for three-point loading and Procedure B is used for four-point loading. This test method was developed for optimum use with continuous-fiber-reinforced polymer matrix composites and differs in several respects from other flexure methods, including the use of a standard span-to-thickness ratio of 32:1 versus the 16:1 ratio used by Test Methods D 790 (a plastics-focused method covering three-point flexure) and D 6272 (a plastics-focused method covering four-point flexure).

This test method is intended to interrogate long-beam strength in contrast to the short-beam strength evaluated by Test Method D 2344/D 2344M.

Flexural properties determined by these procedures can be used for quality control and specification purposes, and may find design applications.

These procedures can be useful in the evaluation of multiple environmental conditions to determine which are design drivers and may require further testing.

These procedures may also be used to determine flexural properties of structures.

1.1 This test method determines the flexural stiffness and strength properties of polymer matrix composites.

1.1.1 Procedure A—A three-point loading system utilizing center loading on a simply supported beam.

1.1.2 Procedure B—A four-point loading system utilizing two load points equally spaced from their adjacent support points, with a distance between load points of one-half of the support span.

Note 1—Unlike Test Method D 6272, which allows loading at both one-third and one-half of the support span, in order to standardize geometry and simplify calculations this standard permits loading at only one-half the support span.

1.2 For comparison purposes, tests may be conducted according to either test procedure, provided that the same procedure is used for all tests, since the two procedures generally give slightly different property values.

1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the inch-pound units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.