An Integrated Computational-Experimental Approach to Three-dimensional Fracture in Polymer-Ceramic Composites

复合材料因其具有高强度和刚度重量比的独特性能而被用于航天器、飞机、汽车和海军舰艇。它们也用于生物工程和电子设备;混凝土是一种复合材料，是当今使用最广泛的材料之一。了解它们的行为对于推进这些材料的设计非常重要，因为为进一步加强或消除它们而采取的措施有时会产生违反直觉甚至适得其反的结果。该奖项支持通过检查三维力学和微观结构水平上的失效演化来理解复合材料材料性能的基础研究。实验和模拟的综合结合将用于研究它们的行为，重点是聚合物陶瓷复合材料。该项目将回答有关微观尺度上的竞争机制的基本问题，这些竞争机制导致微观结构和所得复合材料性能之间的反直觉关系。新的知识和工具将导致复合材料设计的进步，并显著影响这些材料的广泛应用，从而影响国家健康，繁荣和福利;并确保国防。该项目中的外联和教育活动将通过在PI实验室进行研究，扩大本科生和研究生，特别是妇女和其他代表性不足的群体对STEM科目的参与。提出了一种新的计算方法--连续-不连续粒子法（CDPM），该方法结合了传统连续方法在基础力学和数学基础上的优势，以及离散方法在模拟任意复杂三维断裂问题上的优势。该方法允许过渡故障下的无网格颗粒离散的连续介质力学的基础上，一个离散的裂缝网络类似于离散颗粒的方法。提出了一种使用微X射线计算机断层扫描（micro-CT）和原位力学测试仪的方法，该方法产生3D全场力学测量。其他材料表征方法，如拉伸测试，纳米压痕，扫描电子显微镜也将被用来补充原位实验。实验和模拟将紧密结合，以制定和验证数值模型，用于预测具有不同填料形态的聚合物-陶瓷复合材料的复合刚度、强度和韧性，并阐明该结构的根本原因-该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准。

Composite materials are used in spacecrafts, aircrafts, automobiles, and naval vessels for their unique property to provide high strength- and stiffness-to-weight ratios. They are also used in bioengineering and electronic devices; and concrete is a composite that is one of the most widely used materials today. Understanding their behavior is important to advance the design of these materials, as measures taken to further strengthen or stiffen them can sometimes yield counterintuitive or even counterproductive results. This award supports fundamental research on understanding the material properties of composites by examining the three-dimensional mechanics and failure evolution on the microstructural level. An integrated combination of experiments and simulations will be used to study their behavior, with a focus on polymer-ceramic composites. This project will answer fundamental questions about the competing mechanisms on the microscale that lead to the counterintuitive relations between microstructure and resulting composite properties. The new knowledge and tools will lead to advances in the design of composites, and significantly impact the broad range of applications in which these materials are used, thereby impacting national health, prosperity, and welfare; and securing the national defense. The outreach and educational activities in this project will broaden the participation of undergraduate and graduate students, particularly women and from other underrepresented groups, in STEM subjects through research in the PIs' labs. The outreach activities with visiting students from Africa also intends to inspire interest of African-American students in STEM subjects.A new computational approach called the continua-discontinua particle method (CDPM) is proposed which combines the strengths of traditional continuum-based methods in fundamental mechanics and mathematically grounded principles, with the strengths of discrete methods in simulating arbitrary complex three-dimensional fracture. The method allows the transition under failure from a meshfree particle discretization based on continuum mechanics, to that of a discrete fracture network similar to discrete particle methods. An approach using micro X-ray computed tomography (micro-CT) and an in-situ mechanical tester is proposed, which yields 3D full-field mechanical measurements. Other material characterization methods, such as tensile testing, nanoindentation, and scanning electron microscopy will also be employed to compliment the in-situ experiments. The experiments and simulations will be closely integrated to both formulate and validate the numerical models for prediction of composite stiffness, strength, and toughness of polymer-ceramic composites with varying filler morphology, as well as illuminate the underlying causes of the structure-property relationships in these materials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.