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 D6272, 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