Electrical Impedance Characterization of Discontinuous Conductive Fiber Composites

本工作的前提是，具有不连续的，高导电纤维的复合材料的电阻抗响应可以用来表征其微观结构（纤维粘合，取向，数密度等）。并监测加载时的重要变化，包括应变和永久损坏效应（例如，基体开裂和纤维脱粘、断裂和拔出）。 这种能力是需要控制制造和部署的“智能”，自我监测结构复合材料。 由于这样的阻抗响应的必要要求高导电纤维，适度的导电矩阵，和一个频率可切换的界面阻抗已经确定，本项目将研究水泥基体（钢或碳纤维水泥）和陶瓷基体（碳化硅在氮化硅）复合材料的阻抗响应。 实验室“物理”模拟的组合（例如，将进行单根导线/纤维在电介质中的测试（与NIST合作）、基于像素的计算机建模和实际复合材料研究（单根纤维拔出、体积压缩和切口梁拉伸测试），后者将适当配备仪器以进行同步阻抗测量。 本项目将使用阻抗谱法研究复合材料在加载过程中的微观结构和微观结构变化。 所获得的结果应适用于广泛的复合材料，包括水泥基，陶瓷基，甚至聚合物基系统（如果上述条件得到满足），是一个重要的第一步，在新的自我监控复合材料和方法的发展。 以及提高我们对这些复合材料的理解，阻抗谱技术将发展成为一个可靠的表征工具，微观结构分析。 除了对两名研究生和几名大学生进行材料科学和工程方面的培训外，该项目的材料和经验将纳入向非理科大学生讲授科学和工程原理的课程。

The premise of this work is that the electrical impedance response of composites with discontinuous, highly-conductive fibers can be employed to characterize their microstructure (fiber bonding, orientation, number density, etc.) and to monitor important changes upon loading, including strain and permanent damage effects (e.g., matrix cracking and fiber debonding, fracture and pullout). Such capabilities are needed for the controlled fabrication and deployment of 'smart', self-monitoring structural composites. Since the necessary requirements for such an impedance response-highly conductive fibers, a moderately conductive matrix, and a frequency-switchable interfacial impedance-have been identified, this project will study the impedance response of cementitious matrix (steel or carbon fibers in cement) and ceramic matrix (SiC in silicon nitride) composites. A combination of laboratory 'physical' simulations (e.g., single wire/fiber in a dielectric medium), pixel-based computer modeling (in collaboration with NIST), and actual composite studies (single fiber pullout, bulk compressive, and notched-beam tensile tests) will be carried out, with the latter appropriately instrumented for simultaneous impedance measurements. %%%This project will study the microstructure and microstructural changes during loading of composite materials using impedance spectroscopy. The results obtained should be applicable to a broad range of composites, including cement-matrix, ceramic-matrix, and even polymer-matrix systems (if the above-mentioned conditions are met) and are an important first step in the development of novel self-monitoring composite materials and methodology. As well as improving our understanding of these composites, the impedance spectroscopy technique will be developed into a reliable characterization tool for microstructural analysis. In addition to the training of two graduate students and several undergraduates in materials science and engineering, the materials and experiences from the project will be incorporated in a course teaching science and engineering principles to non-science undergraduates.***