1.1 该试验方法确定了聚合物基复合材料在拉伸循环载荷下的疲劳行为。复合材料形式仅限于连续纤维或不连续纤维增强复合材料，其弹性性能相对于测试方向特别是正交异性的。该试验方法仅限于承受恒定振幅单轴平面内载荷的无切口试样，其中载荷是根据试验控制参数定义的。 1.2 该测试方法提供了两个程序，每个程序定义了不同的测试控制参数。 1.2.1 程序A-- 一种系统，其中测试控制参数为载荷（应力），并控制机器，使试样经受重复的恒定振幅载荷循环。在该程序中，可以使用工程应力或施加的载荷作为恒定振幅疲劳变量来描述测试控制参数。 1.2.2 程序B-- 一种系统，其中测试控制参数是加载方向上的应变，并控制机器，使试样经受重复的恒定振幅应变循环。 在该程序中，可以使用加载方向上的工程应变作为恒定振幅疲劳变量来描述测试控制参数。 1.3 以国际单位制或英寸磅单位表示的数值应单独视为标准。每个系统中规定的值不一定是完全相等的；因此，为了确保符合标准，每个系统应独立使用，并且两个系统的值不得组合。 1.3.1 文本中的英寸- 括号中显示了磅单位。 1.4 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.5 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ===意义和用途====== 5.1 该测试方法旨在为材料规范、研发、质量保证以及结构设计和分析提供拉伸疲劳数据。主要测试结果是试样在特定载荷和环境条件下的疲劳寿命。重复试验可用于获得特定材料类型、层压板堆叠顺序、环境和载荷条件下的疲劳寿命分布。疲劳寿命数据统计分析指南，如线性应力寿命的确定（S- N） 或应变寿命（ε-N）曲线，可在实践中找到 E739 。 5.2 该试验方法可用于研究聚合物基复合材料的疲劳损伤，如微观裂纹、纤维断裂或分层的发生。 3. 试样的残余强度或刚度，或两者都可能因这些损伤机制而发生变化。刚度损失可以通过在选定的循环间隔中断循环载荷来量化，以使用试验方法中的模量确定程序获得准静态轴向应力-应变曲线 D3039/D3039米 与疲劳损伤相关的强度损失可以通过使用试验方法中断循环载荷以获得静态强度来确定 D3039/D3039米 。 注1: 该试验方法可作为进行张力-张力变幅加载的指导。这些信息有助于理解复合材料结构在谱载荷条件下的疲劳行为，但本试验方法未涵盖这些信息。

1.1 This test method determines the fatigue behavior of polymer matrix composite materials subjected to tensile cyclic loading. The composite material forms are limited to continuous-fiber or discontinuous-fiber reinforced composites for which the elastic properties are specially orthotropic with respect to the test direction. This test method is limited to unnotched test specimens subjected to constant amplitude uniaxial in-plane loading where the loading is defined in terms of a test control parameter. 1.2 This test method presents two procedures where each defines a different test control parameter. 1.2.1 Procedure A— A system in which the test control parameter is the load (stress) and the machine is controlled so that the test specimen is subjected to repetitive constant amplitude load cycles. In this procedure, the test control parameter may be described using either engineering stress or applied load as a constant amplitude fatigue variable. 1.2.2 Procedure B— A system in which the test control parameter is the strain in the loading direction and the machine is controlled so that the test specimen is subjected to repetitive constant amplitude strain cycles. In this procedure, the test control parameter may be described using engineering strain in the loading direction as a constant amplitude fatigue variable. 1.3 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. 1.3.1 Within the text the inch-pound units are shown in brackets. 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.5 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. ====== Significance And Use ====== 5.1 This test method is designed to yield tensile fatigue data for material specifications, research and development, quality assurance, and structural design and analysis. The primary test result is the fatigue life of the test specimen under a specific loading and environmental condition. Replicate tests may be used to obtain a distribution of fatigue life for specific material types, laminate stacking sequences, environments, and loading conditions. Guidance in statistical analysis of fatigue life data, such as determination of linearized stress life (S-N) or strain-life (ε-N) curves, can be found in Practice E739 . 5.2 This test method can be utilized in the study of fatigue damage in a polymer matrix composite such as the occurrence of microscopic cracks, fiber fractures, or delaminations. 3 The specimen's residual strength or stiffness, or both, may change due to these damage mechanisms. The loss in stiffness may be quantified by discontinuing cyclic loading at selected cycle intervals to obtain the quasi-static axial stress-strain curve using modulus determination procedures found in Test Method D3039/D3039M . The loss in strength associated with fatigue damage may be determined by discontinuing cyclic loading to obtain the static strength using Test Method D3039/D3039M . Note 1: This test method may be used as a guide to conduct tension-tension variable amplitude loading. This information can be useful in the understanding of fatigue behavior of composite structures under spectrum loading conditions, but is not covered in this test method.