Collaborative Research: Interactions between a Propagating Matrix Crack and Inclusions in Particulate Composites: Experiments and Modeling

目的与方法：聚合物基颗粒复合材料的宏观响应是由微观力学控制的。因此，连接宏观和微观尺度是设计下一代微米和亚微米尺寸填料材料的核心。最近对填充聚合物的研究得出了与直觉相反的断裂韧性结果，当填料的尺寸和填料与基体的粘合强度等特性发生变化时。这激发了关于在低和高加载速率下扩展裂纹如何与嵌入夹杂物相互作用的深入研究。本研究将采用实验和计算方法来研究相对柔顺的基体中的刚性夹杂物。实验工作将包括宏观（光学干涉测量、高速成像）和微观（显微镜、表面剖面仪）对断裂过程的测量。裂纹-夹杂相互作用问题的边界元分析将通过计算来解决。测量和计算将协同用于确定新的失效机制以及验证现有的失效机制。更广泛的社会影响：聚合物基颗粒复合材料被广泛应用于生物水泥、导电粘合剂、句法结构泡沫、防刮涂料、固体推进剂、纳米复合材料等领域。了解一般的机械特性，特别是失效特性，对于涉及这些材料的结构系统的安全性和可靠性至关重要。拟议的研究旨在通过奥本大学和南阿拉巴马大学的研究人员之间的合作来解决上述问题。在这个项目中，学生将接受材料加工、材料的机械和光学特性以及数值建模方面的培训。属于代表性不足群体的学生将被鼓励参与该项目。研究成果将通过档案期刊、专题讨论会和万维网传播。

Objectives and approaches: It is well known that macro scale responses of polymer-based particulate composites are controlled by micro scale mechanics. Hence bridging macro and micro scales is central to the design of next generation materials with micron and sub-micron size fillers. Recent investigations on filled polymers have produced counterintuitive fracture toughness results when filler characteristics such as the size and filler-matrix adhesion strengths are varied. This has motivated the proposed in depth study on how a propagating crack interacts with embedded inclusions under low and high rates of loading. Stiff inclusions in a relatively compliant matrix will be targeted in this research using experimental and computational methods. The experimental work will include aspects of macro (optical interferometry, high-speed imaging) and micro (microscopy, surface profilers) measurements of the fracture process. Boundary element analyses of crack-inclusion interaction problems will be addressed computationally. The measurements and computations will be utilized synergistically for identifying new failure mechanisms as well as validating the prevailing ones. Broader societal impact: Polymer-based particulate composites are found in a wide range of applications as biocements, electrically conducting adhesives, syntactic structural foams, scratch resistant coatings, solid propellants, nanocomposites, to name a few. Understanding the mechanical characteristics in general and failure properties in particular is central to the safety and reliability of structural systems involving these materials. The proposed research is aimed towards addressing the above mentioned issues through collaboration between researchers at Auburn University and Univ of S. Alabama. During this project, students will be trained in materials processing, mechanical and optical characterization of materials as well as numerical modeling. Students belonging to underrepresented groups will be encouraged to participate in the project. Research outcome will be disseminated through archival journals, presentations at focused symposia, and world-wide-web.