Normas astm en plasticos

NOTICE: This standard has either been superseded and replaced by a new version or discontinued. Contact ASTM International (www.astm.org) for the latest information.
Designation: D 790 – 00
An American National Standard

Standard Test Methods for

Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials1
This standard is issued under the fixeddesignation D 790; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense.1. Scope * 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 semirigid materials. However, flexural strength cannotbe 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 three-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 atcomparatively small deflections. 1.1.2 Procedure B, designed particularly for those materials that undergo large deflections during testing. 1.1.3 Procedure A shall be used for measurement of flexural properties, particularly 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 Atends to exhibit lower standard deviations than comparable data obtained by means of Procedure B. 1.2 Comparative tests may be run in accordance with either procedure, provided that the procedure is found satisfactory for the material being tested. 1.3 The values stated in SI units are to be regarded as the standard. The values provided in parentheses are for information only. 1.4 This standarddoes 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.
NOTE 1—These test methods are not technically equivalent to ISO 178.
1 These test methods are under the jurisdiction of ASTMCommittee D20 on Plastics and are the direct responsibility of Subcommittee D20.10 on Mechanical Properties. Current edition approved Nov. 10, 2000. Published January 2001. Originally published as D 790 – 70. Last previous edition D 790 – 99.

2. Referenced Documents 2.1 ASTM Standards: D 618 Practice for Conditioning Plastics and Electrical Insulating Materials for Testing2 D 638 Test Method forTensile Properties of Plastics2 D 883 Terminology Relating to Plastics2 D 4000 Classification System for Specifying Plastic Materials3 D 5947 Test Methods for Physical Dimensions of Solid Plastic Specimens4 D 6272 Test Method for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials by Four-Point Bending4 E 4 Practices for Load Verification of Testing Machines5 E691 Practice for Conducting an Interlaboratory Test Program to Determine the Precision of Test Methods6 3. Terminology 3.1 Definitions—Definitions of terms applying to these test methods appear in Terminology D 883 and Annex A1 of Test Method D 638. 4. Summary of Test Method 4.1 A bar of rectangular cross section rests on two supports and is loaded by means of a loading nose midway between the...