1.1 本试验方法( 注1 )用于确定在标准单搭接接头试样上以及在规定的制备和测试条件下测试时，大面积接头中粘合剂的对比剪切强度。粘合剂在小面积接缝和大面积接缝中的反应不同( 注2 ). 注1: 虽然本试验方法旨在用于金属对金属的应用，但如果考虑到塑料被粘物的厚度和硬度，则可用于测量使用塑料被粘体的粘合剂的剪切性能。塑料被粘物可能需要倍增器或粘结片，以防止被粘物中的轴承失效。 注2: 这种变化可能受到粘合剂密度、流动特性、固化速率、凝胶时间、载体组成、截留的挥发物、固化过程中释放的挥发物等的影响。 以及固化循环变量，包括:温度、时间、压力、升温速率、冷却速率等。除了加工变量外，接头尺寸还会改变对粘合剂的约束程度，以及在机械或热载荷期间接头边缘处感应拉伸载荷的影响。 1.2 以国际单位制表示的数值应视为标准。括号中给出的值仅供参考。 1.3 本标准并不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建立适当的安全、健康和环境实践，并确定监管限制的适用性。 1.4 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《国际标准、指南和建议制定原则决定》中确立的国际公认标准化原则制定的。 =====意义和用途====== 4.1 该测试方法非常有用，因为接头配置紧密模拟了许多粘结组件的实际接头配置。被粘物的表面处理可以影响粘合剂的表观剪切强度，并且可以是正在研究的变量之一。 4.2 该试验方法也可用作层压组件的过程中质量控制试验。在实践中，层压组件要么制作得过大，并从中取出试样，要么对一定比例的组件进行破坏性测试。 4.3 误用本试验方法获得的强度值作为结构接头的设计容许应力值可能导致产品失效、财产损失和人身伤害。从给定的小单搭接试样获得的粘合剂的表观剪切强度可能不同于从由不同的被粘物或通过不同的粘结工艺制成的接头获得的粘合剂。使用环境中温度和湿度的正常变化会导致被粘物和粘合剂膨胀和收缩。被粘物和粘合剂可能具有不同的热膨胀系数和湿膨胀系数。 4.3.1 即使在小样本中，短期环境变化也会在粘合剂中引起内应力或化学变化，从而永久影响粘合剂的表观强度和其他机械性能。 如果在较大的结构接头中使用不同类型的被粘物，则预测变化环境中的接头行为的问题甚至更困难。 4.4 使用单搭接试样测量的表观剪切强度不适用于确定设计结构接头的设计许用应力，该结构接头在任何方面都不同于未对接头和粘合性能进行彻底分析和了解的试验接头。 4.5 单搭接试验可用于比较和选择粘合剂或粘合工艺对疲劳和环境变化的敏感性，但此类比较必须非常谨慎，因为不同的粘合剂在不同的接头中可能会有不同的反应。 审查指南 D4896型 以进一步讨论用于解释粘结单搭接接头数据的概念。

1.1 This test method ( Note 1 ) is intended for determining the comparative shear strengths of adhesives in large area joints when tested on a standard single-lap-joint specimen and under specified conditions of preparation and testing. Adhesives respond differently in small versus large area joints ( Note 2 ). Note 1: While this test method is intended for use in metal-to-metal applications, it may be used for measuring the shear properties of adhesives using plastic adherends, provided consideration is given to the thickness and rigidity of the plastic adherends. Doublers or bonded tabs may be required for plastic adherends to prevent bearing failure in the adherends. Note 2: This variation can be influenced by adhesive density, flow characteristics, cure rate, gel time, carrier composition, entrapped volatiles, volatiles released during cure, etc. and also by cure cycle variables including: temperature, time, pressure, rise rate to temperature, cool-down rate, etc. In addition to the processing variables joint size changes the level of constraint on the adhesive as well as the influence of induced tensile loads at the edge of the joint during mechanical or thermal loading. 1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. 1.3 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. 1.4 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 ====== 4.1 This test method is useful in that the joint configuration closely simulates the actual joint configuration of many bonded assemblies. Surface preparation of the adherends can affect the apparent shear strength of the adhesive and can be one of the variables under study. 4.2 This test method is also useful as an in-process quality control test for laminated assemblies. In practice the laminated assembly is either made over size and test specimens removed from it or a percentage of the assemblies are destructively tested. 4.3 The misuse of strength values obtained from this test method as design allowable stress values for structural joints could lead to product failure, property damage, and human injury. The apparent shear strength of an adhesive obtained from a given small single-lap specimen may differ from that obtained from a joint made with different adherends or by a different bonding process. The normal variation of temperature and moisture in the service environment causes the adherends and the adhesive to swell and shrink. The adherends and adhesive are likely to have different thermal and moisture coefficients of expansion. 4.3.1 Even in small specimens, short-term environmental changes can induce internal stresses or chemical changes in the adhesive that permanently affect the apparent strength and other mechanical properties of the adhesive. The problem of predicting joint behavior in a changing environment is even more difficult if a different type of adherend is used in a larger structural joint than was used in the small specimen. 4.4 The apparent shear strength measured with a single-lap specimen is not suitable for determining design allowable stresses for designing structural joints that differ in any manner from the joints tested without thorough analysis and understanding of the joint and adhesive behaviors. 4.5 Single-lap tests may be used for comparing and selecting adhesives or bonding processes for susceptibility to fatigue and environmental changes, but such comparisons must be made with great caution since different adhesives may respond differently in different joints. Review Guide D4896 for further discussion of concepts for interpretation of adhesive-bonded single-lap joint data.