IMR: Development/Acquisition of a Mixed-Mode Fracture Testing Instrument for Research and Education in Adhesion Science

在汽车、航空航天、民用基础设施、生物医学和微电子领域等广泛应用中，粘合剂粘合已成为连接部件的重要手段。这些粘接的令人满意的性能要求在使用寿命期间保持结构的完整性，因为它们经常受到恒载、冲击和/或疲劳的影响，同时暴露在温度和湿度等环境挑战下。目前迫切需要提高对粘结接头抗断裂性能的理解，以及如何将这些性能纳入有意义且可靠的粘结结构设计程序中。在I型（开口）、II型（正向剪切）和III型（撕裂）载荷的组合作用下，节理往往会因断裂扩展而失效。由于断裂能取决于模态混合，因此通过进行纯模态和混合模态试验，可以生成一系列模态混合的综合破坏包络。该提案寻求资金来开发一种独特的仪器，能够轻松地改变粘接梁试件断裂测试的模式组合。目前，通过使用不同的测试配置来实现不同的模式混合，增加了复杂性并模糊了有意义的比较。已经开发了几种固定装置来改变给定试样几何形状在有限范围内的模式混合，但是这些技术使用起来很麻烦，并且在适用性上受到限制。这些并发症是发展更好地理解模式混合对断裂特性和破坏轨迹影响的主要障碍。这些限制将在很大程度上被本文提出的单元所克服，它通过使用与许多领域相关的方便和有效的测试方法，为获得新的科学见解提供了巨大的潜力。拟议的仪器将围绕一个定制的负载框架构建，包括双致动器、负载传感器、位移传感器、控制器和数据采集系统。通过独立调整促动器的大小和相位，任何期望的断裂能和模态混合都可以应用于常用的ASTM标准双悬臂梁试件。由于模态混合可以在测试过程中很容易地改变，因此可以研究模态混合的影响，即使是在单个试样内扩展剥离。该仪器将具有独特的科学和工程能力，用于表征混合模式断裂，开发断裂包层，研究应力状态和空间变化的材料特性之间的复杂相互作用以及它们如何影响破坏轨迹。该装置有望在粘合剂应用的许多领域发挥作用，也可以很容易地扩展到其他学科，例如复合材料或其他层压材料的层间性能研究，这对许多航空航天，汽车和基础设施应用都很重要。除了科学上的优点，许多工业领域生产或使用粘合剂和复合材料的公司都有望从这个简单的装置中获得方便的见解。由于样品已经符合ASTM标准并且易于制作，因此将减少使用和广泛采用该技术的障碍。从本质上讲，我们将能够获得大量额外的信息，关于材料的性能使用样本，已经在普遍使用。一名研究生和一名本科生将参与开发工作，获得仪器设计、构造和校准方面的重要经验，以及计算机接口和编程技能。该单元将由与我们跨学科的粘合剂和密封剂科学中心相关的不同群体的学生和教师使用。这种独特的研究能力将很好地补充我们现有的用于表征粘附性和复合材料特性的各种设备，并有望吸引当前赞助商以及未来潜在资金来源的极大兴趣，包括工业和政府实验室。该装置将提供一个非常灵活的仪器，以加强胶粘剂的机械性能的研究，也提供有用的新见解相关的聚合物和表面科学在这个跨学科领域的粘附。粘合剂粘合已成为广泛应用中连接部件的重要手段，包括汽车，航空航天，民用基础设施，生物医学和微电子领域。这些粘接的令人满意的性能要求在使用寿命期间保持结构的完整性，因为它们经常受到恒载、冲击和/或疲劳的影响，同时暴露在温度和湿度等环境挑战下。目前迫切需要提高对粘结接头抗断裂性能的理解，以及如何将这些性能纳入有意义且可靠的粘结结构设计程序中。节理在拉伸和剪切双重载荷作用下，常因断裂扩展而失效。由于断裂能取决于模态组合，因此通过进行纯模态和混合模态试验，可以生成一系列模态组合的综合破坏包络。这些提供了对失效过程的重要理解，并避免了非保守的设计空间。该提案寻求资金来开发一种独特的仪器，能够轻松地改变粘接梁试件断裂测试的模式组合。目前，不同的模式组合是通过使用不同的测试配置来实现的，这增加了复杂性，并模糊了有意义的比较。已经开发了几种固定装置来改变给定试样几何形状在有限范围内的模式组合，但是这些技术使用起来很麻烦，并且在适用性上受到限制。这些限制将在很大程度上被本文提出的单元所克服，它通过使用与许多领域相关的方便和有效的测试方法，为获得新的科学见解提供了巨大的潜力。拟议的仪器将围绕一个定制的负载框架构建，包括双致动器、负载传感器、位移传感器、控制器和数据采集系统。通过独立调整执行器的大小和相位，任何期望的断裂能和模态组合都可以应用于常用的双悬臂梁试件。该仪器将具有独特的科学和工程能力，用于设计和科学应用中表征混合模式断裂。该装置有望在粘合剂应用的许多领域发挥作用，也可以很容易地扩展到其他学科，例如复合材料或其他层压材料的层间性能研究，这对许多航空航天，汽车和基础设施应用都很重要。除了科学上的优点，许多工业领域生产或使用粘合剂和复合材料的公司都有望从这个简单的装置中获得方便的见解。由于这些样品已经是美国测试和材料协会的标准，并且易于制作，因此将减少使用和广泛采用该技术的障碍。从本质上讲，我们将能够获得大量额外的信息，关于材料的性能使用样本，已经在普遍使用。该设备的开发将促进粘附科学、科学仪器设计和编程方面的培训和研究工作，为我们跨学科的粘合剂和密封剂科学中心的本科生和研究生提供服务。

Adhesive bonding has become an essential means for joining components in a wide range of applications, including automotive, aerospace, civil infrastructure, biomedical, and microelectronic fields. Satisfactory performance of these bonds requires retaining structural integrity over the service life where they are often subjected to dead loads, impact, and/or fatigue, while exposed to environmental challenges such as temperature and humidity. A significant need exists for improved understanding of the fracture resistance of bonded joints, and how these properties can be incorporated into meaningful and robust design procedures for bonded structures. Joints often fail by fracture propagating under some combination of mode I (opening), mode II (forward shear), and mode III (tearing) loading. Because fracture energies depend on mode mixity, comprehensive failure envelopes for a range of mode mixities are generated by conducting pure and mixed mode tests. This proposal seeks funding to develop a unique instrument capable of easily varying the mode mix for fracture testing of adhesively bonded beam specimens. Currently, different mode mixities are achieved by using different test configurations, increasing complexity and obscuring meaningful comparisons. Several fixtures have been developed to vary the mode mixity over a limited range for a given specimen geometry, but these techniques are cumbersome to use and limited in their applicability. These complications are a major hindrance to developing an improved understanding of the effects of mode mixity on fracture properties and locus of failure. These limitations will be largely overcome by the unit proposed herein, which offers significant potential for new scientific insights gained through use of a convenient and efficient test method relevant to many fields. The proposed instrument will be built around a customized load frame complete with dual actuators, load cells, displacement transducers, controllers, and data acquisition system. By independently adjusting the magnitude and phase of the actuators, any desired fracture energy and mode mixity may be applied to commonly used, ASTM standard, double cantilever beam specimens. Because the mode mixity can be easily changed during a test, one can investigate the effects of mode mix, even as a debond propagates within a single specimen. The instrument will have unique scientific and engineering capabilities for characterizing mixed mode fracture, developing fracture envelopes, and investigating the complex interactions between stress state and spatially varying material properties and how they affect locus of failure. The unit is expected to be useful in many areas of adhesive utilization and can also be readily extended to other disciplines, such as the study of interlaminar properties of composites or other laminated materials, important for many aerospace, automotive, and infrastructure applications. In addition to the scientific merits, companies producing or using adhesives and composite materials for many industrial fields are expected to gain from the insights that can conveniently be obtained with this simple unit. Because the specimens are already an ASTM standard and are easily fabricated, barriers will be reduced for the use and broader adoption of this technology. In essence, we will be able to gain a great deal of additional information about the material performance using specimens that are already in common use. A graduate student and an undergraduate student will participate in the development effort, obtaining significant experience in instrument design, construction, and calibration, along with computer interfacing and programming skills. The unit will be used by a diverse group of students and faculty associated with our interdisciplinary Center for Adhesive and Sealant Science. This unique research capability will nicely complement the wide array of equipment we have available for characterizing adhesion and composite properties, and is expected to attract significant interest from current sponsors as well as potential sources of future funding, including industry and government laboratories. The unit will offer a very flexible instrument to enhance the research of mechanical properties of adhesives, and also provide useful new insights related to polymer and surface science in this interdisciplinary field of adhesion.%%% Adhesive bonding has become an essential means for joining components in a wide range of applications, including automotive, aerospace, civil infrastructure, biomedical, and microelectronic fields. Satisfactory performance of these bonds requires retaining structural integrity over the service life where they are often subjected to dead loads, impact, and/or fatigue, while exposed to environmental challenges such as temperature and humidity. A significant need exists for improved understanding of the fracture resistance of bonded joints, and how these properties can be incorporated into meaningful and robust design procedures for bonded structures. Joints often fail by fracture propagating under some combination of tensile and shear mode loadings. Because fracture energies depend on mode combinations, comprehensive failure envelopes for a range of mode combinations are generated by conducting pure and mixed mode tests. These provide important understanding of the failure process, and avoid non-conservative design space. This proposal seeks funding to develop a unique instrument capable of easily varying the mode mix for fracture testing of adhesively bonded beam specimens. Currently, different mode combinations are achieved by using different test configurations, increasing complexity and obscuring meaningful comparisons. Several fixtures have been developed to vary the mode combination over a limited range for a given specimen geometry, but these techniques are cumbersome to use and limited in their applicability. These limitations will be largely overcome by the unit proposed herein, which offers significant potential for new scientific insights gained through use of a convenient and efficient test method relevant to many fields. The proposed instrument will be built around a customized load frame complete with dual actuators, load cells, displacement transducers, controllers, and a data acquisition system. By independently adjusting the magnitude and phase of the actuators, any desired fracture energy and mode mix may be applied to commonly used, double cantilever beam specimens. The instrument will have unique scientific and engineering capabilities for characterizing mixed mode fracture for design and scientific applications. The unit is expected to be useful in many areas of adhesive utilization and can also be readily extended to other disciplines, such as the study of interlaminar properties of composites or other laminated materials, important for many aerospace, automotive, and infrastructure applications. In addition to the scientific merits, companies producing or using adhesives and composite materials for many industrial fields are expected to gain from the insights that can conveniently be obtained with this simple unit. Because the specimens are already an American Society for Testing and Materials standard and are easily fabricated, barriers will be reduced for the use and broader adoption of this technology. In essence, we will be able to gain a great deal of additional information about the material performance using specimens that are already in common use. The development of the device will promote the training and research effort in adhesion science, scientific instrument design and programming for a diverse group of undergraduate and graduate students associated with faculty in our interdisciplinary Center for Adhesive and Sealant Science.