Experimental study of Interfacial and Sub-Interfacial Quasistatic Crack Growth

研究 的 失效机制 双材料 和多相材料系统的发展是由多相部件的工业重要性所推动的， 金属、陶瓷和聚合物复合材料。 了解 失败 这些系统中的模式是 相关 应用中 从先进的复合材料 飞机结构到电子器件的封装。 这种系统的失效可能是由于多种机制造成的：脆性基体的宏观和微观开裂、沿不同材料之间的界面沿着开裂、分层等，这取决于材料系统的具体情况。 在美国国家科学基金会先前的研究资助下，PI的研究小组开发了一种紧凑的偏光镜/剪切干涉仪（PSI）， 作为 要么 偏振镜或剪切干涉仪。 这个单一的设备允许人们从光学各向异性材料（如Homolite和环氧树脂）以及基本上光学各向同性材料（如PMMA和玻璃）获得应力状态。 材料失配参数的范围可以 通过组合光学各向同性和各向异性的模型材料提供的材料基本上跨越了 通常 获得 在 技术 重要的双材料系统，因此，结果从模型材料 组合具有广泛的适用性。 直接 光学 裂纹萌生数据 从静态加载的双材料系统获得。 在 这 工作，全场光学干涉信息将获得准静态扩展界面和亚界面裂纹周围的应力状态。 本研究中将使用先前开发的用于监测裂纹萌生的光学干涉仪，并结合相对高速的视频记录仪（6000 帧/参见）来监控准静态传播。 与光学数据的视频记录同时，还将使用安装在加载装置上的测力传感器和线性变化位移传感器记录载荷和载荷点位移数据，并且将使用这些数据。 在数值模拟中， 使用 来解释实验数据。 将对双材料和多层夹层试样进行一系列实验。 特别感兴趣的现象是：* 界面裂纹扩展状态，其中裂纹 传播 完全在界面上 之间 两 不同的材料; * 裂纹扭结制度，其中裂纹开始从 接口 但在材料中扭结， 低 韧性; 裂纹从界面扭结，并继续在 韧性较低的材料; * 夹层中的裂纹隧穿机制。 收集的数据和进行的分析应该为我们提供更多的信息，以便更好地了解 的 裂纹扭结和 裂纹 隧道现象，除了证实目前的知识状态的问题，界面裂纹萌生和裂纹平行。

Study of failure mechanisms in bimaterial and multiphase material systems is motivated by the industrial importance of multiphase components made from metals, ceramics and polymer composite materials. An understanding of failure modes in these systems is relevant in applications ranging from advanced composite aircraft structures to packaging of electronic devices. Failure in such systems can be due to a variety of mechanisms: macro- and microcracking of a brittle matrix, cracking along interfaces between dissimilar materials, delaminations and so on depending on the specifics of the material system. Under a prior research grant from the NSF, the PI's research group has developed a compact Polariscope/Shearing Interferometer (PSI) that can be used as either a polariscope or a shearing interferometer. This single device allows one to obtain stress states from optically anisotropic materials (such as Homolite and epoxy) as well as essentially optically isotropic materials (such as PMMA and glass). The range of material mismatch parameters that can be provided by combining optically isotropic and anisotropic model materials essentially spans the range that is typically obtained in technologically important bimaterial systems, consequently results from the model material combinations have wide ranging applicability. Direct optical data regarding crack initiation from statically-loaded bimaterial systems have been obtained. In this work, full-field optical interferometric information will be obtained about the stress state around quasi-statically propagating interfacial and sub-interfacial cracks. The optical interferometers previously developed for monitoring crack initiation will be used in this study in conjunction with a relatively high-speed video recorder (6000 frames/see) to monitor quasi-static propagation. Simultaneous with the video recording of the optical data, load and load-point displacement data will also be recorded using a load cell and a linearly-varying displacement transducer mounted on the loading device, and these will be used in numerical modeling that can be of use in interpreting the experimental data. A series of experiments on bimaterial and multilayer sandwich specimens will be conducted. Phenomena of particular interest are: * the interfacial crack propagation regime where the crack propagates entirely on the interface between two dissimilar materials; * the crack kinking regime where the crack starts from the interface but kinks into the material with lower toughness; * the sub-interfacial crack propagation regime after the crack kinks from the interface and continues in the material with lower toughness; * the crack tunneling mechanisms in sandwiched layers. The data gathered, and the analysis performed, should provide us with additional information to gain a better understanding of crack kinking and crack tunneling phenomena, in addition to substantiating the current state of knowledge of issues of interfacial crack initiation and crack paralleling.