1.1 该试验方法测定了具有规定直径的单个通孔的连续纤维增强陶瓷基复合材料（CMC）试样的开孔（缺口）抗拉强度（6 mm或3 毫米）。开孔拉伸（OHT）试验方法确定了单个通孔在环境温度下对连续纤维增强CMC的拉伸强度和应力响应的影响。OHT强度可以与无缺口试样的抗拉强度进行比较，以确定所定义的开孔对CMC材料的抗拉强度和缺口敏感性的影响。如果材料是缺口敏感的，那么材料的OHT强度随着通孔的尺寸而变化。通常，较大的孔引入较大的应力集中并降低OHT强度。 1.2 该试验方法根据试验方法定义了两个基准OHT试样几何形状和一个试验程序 1927年 和 D5766/D5766米 具有确定的层压纤维结构的平坦、直边陶瓷复合材料试样包含单个通孔（6 mm或3 直径mm），在规定的量规截面中以长度和宽度为中心( 图1 )。在环境温度下，沿规定的试验钢筋轴线进行单轴单调拉伸试验，根据试验方法测量施加的力与时间/位移的关系 1927年 .标距长度延伸/应变的测量是可选的，使用伸长计/位移传感器。粘结应变片是可选的，用于测量应变片部分的局部应变和评估弯曲应变。 图1 OHT试样A和B 1.3 裸眼抗拉强度( S OHTx公司 )对于定义的孔径 x （mm）是根据常见航空航天惯例，基于最大作用力和总横截面积计算的极限抗拉强度，不考虑孔的存在（见 4.4 )。净截面抗拉强度( 秒 NSx公司 )也被计算为第二强度特性，考虑到孔对试样横截面积的影响。 1.4 该试验方法主要适用于在多个方向上具有连续纤维增强的陶瓷基复合材料。CMC材料通常是纤维增强的2D层压复合材料，其中层压材料相对于测试方向是平衡和对称的。 具有其他类型钢筋（1D、3D、编织、不平衡）的复合材料可以用这种方法进行测试，同时考虑不同的结构如何影响孔对OHT强度和拉伸应力-应变响应的缺口效应。该试验方法并不直接涉及不连续的纤维增强、晶须增强或颗粒增强陶瓷，尽管此处详述的试验方法可能同样适用于这些复合材料。 1.5 该测试方法可用于具有不同增强纤维和陶瓷基质的各种CMC材料（氧化物复合材料、SiC基质中的碳化硅（SiC）纤维、SiC基体中的碳纤维和碳-碳复合材料）以及具有不同增强结构的CMC。 它也适用于具有广泛孔隙率和密度的CMC。 1.6 附件A1 和 附录X1 说明如何制备和测试具有不同几何形状和孔径的试样，以确定这些变化将如何改变OHT强度特性、确定缺口敏感性以及影响应力-应变响应。 1.7 通过按照试验方法修改试验设备、试样和程序，试验方法可适用于高温OHT试验 C1359年 如中所述 附录X2 试验方法也可适用于环境试验（在中等（<300 °C）温度），根据 7.6 。 1.8 本试验方法中表示的数值符合国际单位制（SI）和 IEEE/ASTM SI 10标准 。 1.9 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。 1.10 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 复合材料的开孔试验用于复合材料工程应用的材料和设计开发 ( 5个- 11 ) 复合材料部件中开孔的存在减少了可用于承载施加的力的横截面面积，产生了应力集中，并产生了可能发生分层的新边缘。复合材料的标准化裸眼测试可以提供关于复合材料如何在裸眼应用中发挥作用以及如何为缺口和孔设计复合材料的有用信息。 5.2 该试验方法定义了两种基准试样几何形状和一种用于产生可比较、可重复的OHT试验数据的试验程序。该测试方法旨在为结构设计容许值、材料规范、材料开发和比较、材料表征和质量保证提供OHT强度数据。可通过该试验方法计算出的机械性能包括: 5.2.1 开孔（缺口）抗拉强度( S OHTx公司 )对于具有孔径的试样 x （毫米）。 5.2.2 净截面抗拉强度( S NSx公司 )对于具有孔径的试样 x （毫米）。 5.2.3 比例极限应力（σ 0 )对于具有给定孔径的OHT试样。 5.2.4 OHT试样的应力响应，如应力-时间或应力-位移图所示。 5.3 开孔拉伸试验提供了具有规定通孔的材料在单轴拉伸应力下的强度和变形信息。影响OHT复合材料强度的材料因素包括:材料成分、复合材料制造方法、钢筋结构（包括钢筋体积、丝束数量和端部- 计数、结构结构和层压板堆叠顺序）和孔隙率。试样的影响因素包括:试样几何形状（包括孔径、宽径比和径厚比）、试样制备（尤其是孔）和试样处理。影响试验的因素包括:试样对准和夹紧、试验速度和试验温度/环境。需要控制应力状态来有效评估任何非线性应力-应变行为，这些行为可能是累积损伤过程（例如，基体开裂、基体/纤维脱胶、分层、纤维拔出和断裂等）的结果，这些过程可能受到测试模式、测试速率、加工效果或环境影响的影响。 其中一些影响可能是应力腐蚀或缓慢（亚临界）裂纹扩展的结果。应力腐蚀和缓慢裂纹扩展因子可以通过以足够快的速率进行测试来最小化，如 12.1.7 。

1.1 This test method determines the open-hole (notched) tensile strength of continuous fiber-reinforced ceramic matrix composite (CMC) test specimens with a single through-hole of defined diameter (either 6 mm or 3 mm). The open-hole tensile (OHT) test method determines the effect of the single through-hole on the tensile strength and stress response of continuous fiber-reinforced CMCs at ambient temperature. The OHT strength can be compared to the tensile strength of an unnotched test specimen to determine the effect of the defined open hole on the tensile strength and the notch sensitivity of the CMC material. If a material is notch sensitive, then the OHT strength of a material varies with the size of the through-hole. Commonly, larger holes introduce larger stress concentrations and reduce the OHT strength. 1.2 This test method defines two baseline OHT test specimen geometries and a test procedure, based on Test Methods C1275 and D5766/D5766M . A flat, straight-sided ceramic composite test specimen with a defined laminate fiber architecture contains a single through-hole (either 6 mm or 3 mm in diameter), centered by length and width in the defined gage section ( Fig. 1 ). A uniaxial, monotonic tensile test is performed along the defined test reinforcement axis at ambient temperature, measuring the applied force versus time/displacement in accordance with Test Method C1275 . Measurement of the gage length extension/strain is optional, using extensometer/displacement transducers. Bonded strain gages are optional for measuring localized strains and assessing bending strains in the gage section. FIG. 1 OHT Test Specimens A and B 1.3 The open-hole tensile strength ( S OHTx ) for the defined hole diameter x (mm) is the calculated ultimate tensile strength based on the maximum applied force and the gross cross-sectional area, disregarding the presence of the hole, per common aerospace practice (see 4.4 ). The net section tensile strength ( S NSx ) is also calculated as a second strength property, accounting for the effect of the hole on the cross-sectional area of the test specimen. 1.4 This test method applies primarily to ceramic matrix composites with continuous fiber reinforcement in multiple directions. The CMC material is typically a fiber-reinforced, 2D, laminated composite in which the laminate is balanced and symmetric with respect to the test direction. Composites with other types of reinforcement (1D, 3D, braided, unbalanced) may be tested with this method, with consideration of how the different architectures may affect the notch effect of the hole on the OHT strength and the tensile stress-strain response. This test method does not directly address discontinuous fiber-reinforced, whisker-reinforced, or particulate-reinforced ceramics, although the test methods detailed here may be equally applicable to these composites. 1.5 This test method may be used for a wide range of CMC materials with different reinforcement fibers and ceramic matrices (oxide-oxide composites, silicon carbide (SiC) fibers in SiC matrices, carbon fibers in SiC matrices, and carbon-carbon composites) and CMCs with different reinforcement architectures. It is also applicable to CMCs with a wide range of porosities and densities. 1.6 Annex A1 and Appendix X1 address how test specimens with different geometries and hole diameters may be prepared and tested to determine how those changes will modify the OHT strength properties, determine the notch sensitivity, and affect the stress-strain response. 1.7 The test method may be adapted for elevated temperature OHT testing by modifying the test equipment, specimens, and procedures per Test Method C1359 and as described in Appendix X2 . The test method may also be adapted for environmental testing (controlled atmosphere/humidity at moderate (<300 °C) temperatures) of the OHT properties by the use of an environmental test chamber, per 7.6 . 1.8 Values expressed in this test method are in accordance with the International System of Units (SI) and IEEE/ASTM SI 10 . 1.9 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. 1.10 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 Open-hole tests of composites are used for material and design development for the engineering application of composite materials ( 5- 11 ) . The presence of an open hole in a composite component reduces the cross-sectional area available to carry an applied force, creates stress concentrations, and creates new edges where delamination may occur. Standardized open-hole tests for composite materials can provide useful information about how a composite material may perform in an open-hole application and how to design the composite for notches and holes. 5.2 The test method defines two baseline test specimen geometries and a test procedure for producing comparable, reproducible OHT test data. The test method is designed to produce OHT strength data for structural design allowables, material specifications, material development and comparison, material characterization, and quality assurance. The mechanical properties that may be calculated from this test method include: 5.2.1 The open-hole (notched) tensile strength ( S OHTx ) for test specimen with a hole diameter x (mm). 5.2.2 The net section tensile strength ( S NSx ) for a test specimen with a hole diameter x (mm). 5.2.3 The proportional limit stress (σ 0 ) for an OHT specimen with a given hole diameter. 5.2.4 The stress response of the OHT test specimen, as shown by the stress-time or stress-displacement plot. 5.3 Open-hole tensile tests provide information on the strength and deformation of materials with defined through-holes under uniaxial tensile stresses. Material factors that influence the OHT composite strength include the following: material composition, methods of composite fabrication, reinforcement architecture (including reinforcement volume, tow filament count and end-count, architecture structure, and laminate stacking sequence), and porosity content. Test specimen factors of influence are: specimen geometry (including hole diameter, width-to-diameter ratio, and diameter-to-thickness ratio), specimen preparation (especially of the hole), and specimen conditioning. Test factors of influence are: specimen alignment and gripping, speed of testing, and test temperature/environment. Controlled stress states are required to effectively evaluate any nonlinear stress-strain behavior which may develop as the result of cumulative damage processes (for example, matrix cracking, matrix/fiber debonding, delamination, fiber pull-out and fracture, etc.) which may be influenced by testing mode, testing rate, processing effects, or environmental influences. Some of these effects may be consequences of stress corrosion or slow (subcritical) crack growth. Stress corrosion and slow crack growth factors can be minimized by testing at sufficiently rapid rates as described in 12.1.7 .