5.1 The parameter K_TL determined by this test method is a measure of the resistance of a polymer matrix composite laminate to notch-tip damage and effective translaminar crack growth under opening mode loading. The result is valid only for conditions in which the damage zone at the notch tip is small compared with the notch length and the in-plane specimen dimensions. Alternately, for materials exhibiting distributed damage in a larger volume, observed force-displacement and discrete damage events are still valid structural responses for certain specific engineering applications.

5.2 This test method can serve the following purposes. In research and development, (a) K_TL data can quantitatively establish the effects of fiber and matrix variables and stacking sequence of the laminate on the translaminar fracture resistance of composite laminates; and (b) quantified distributed damage measurements can be used to validate progressive composite damage models. In structural design, K_TL data can, within the constraints of the specimen geometry and loading, be used to assess composite laminate resistance to damage growth from edge flaws and notches.

5.3 The translaminar fracture toughness, K_TL, as well as distributed damage observations, determined by this test method may be a function of the testing speed and temperature. This test method is intended for room temperature and quasi-static conditions, but it can apply to other test conditions provided that the requirements of 13.2 and 13.3 are met. Application of K_TL in the design of service components should be made with awareness that the test parameters specified by this test may differ from service conditions, possibly resulting in a different material response than that seen in service. Distributed damage observations are also limited to the material and geometry tested, but may be more generally applied to a variety of structural analysis validation applications.

5.4 Not all types of laminated polymer matrix composite materials experience the contained notch-tip damage and effective translaminar crack growth of concern in this test method. In such circumstances, the force-displacement and discrete damage observations – not K_TL – shall be used.

5.5 The reporting section requires items that tend to influence translaminar fracture toughness and discrete damage progression to be reported; these include the following: material, methods of material fabrication, accuracy of lay-up orientation, laminate stacking sequence and overall thickness, specimen geometry, specimen preparation, specimen conditioning, environment of testing, void content, volume percent reinforcement, size and method of notch preparation, specimen/fixture alignment, and speed of testing.

1.1 This test method covers the determination of translaminar fracture toughness, K_TL, for laminated, molded, or pultruded polymer matrix composite materials of various fiber orientations using test results from monotonically loaded notched specimens. If the material response is such that the K_TL calculation is not valid, alternate reporting methods are provided.

1.2 This test method is applicable to room temperature laboratory air environments.

1.3 Composite materials that can be tested by this test method are not limited by thickness or by type of polymer matrix or fiber, provided that the specimen sizes and the test results meet the requirements of this test method. This test method was developed primarily from test results of various carbon fiber – epoxy matrix laminates and from additional results of glass fiber – epoxy matrix, glass fiber-polyester matrix pultrusions and carbon fiber – bismaleimide matrix laminates (1-4, 5, 6).2

1.4 A range of eccentrically loaded, single-edge-notch tension, ESE(T), specimen sizes with proportional planar dimensions is provided, but planar size may be variable and adjusted, with associated changes in the applied test load. Specimen thickness is a variable, independent of planar size.

1.5 Specimen configurations other than those contained in this test method may be used. It is particularly important that the requirements discussed in 5.1 and 5.4 regarding contained notch-tip damage be met when using alternative specimen configurations in conjunction with the K_TL calculation.

1.6 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.

1.6.1 Within the text, the inch-pound units are shown in brackets.

1.7 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.