CAREER: In-Situ Characterization of Materials

9985264 ustundag该基金提出了详细的CAREER计划，该计划将采用中子和x射线衍射仪器的最新改进来表征复合材料中单个相对施加载荷的响应。模型标本的制备基本上是纤维复合材料，从单一纤维到纤维阵列，最后到接近“真实”复合材料几何形状的纤维的三维堆叠。试样在x射线或中子束下加载，以测量各相的应变响应。通过改变外加应力和温度，可以确定一些关键现象，如原位屈服应力、基体或纤维开裂、界面剥离、由于一相蠕变而导致的载荷分担演化、相邻纤维之间的相互作用以及损伤区域的演化。复合材料的整体宏观响应是通过附着在其表面的应变计或延伸计来测量的。主要目标是提供可靠的力学行为数据，这将导致本构方程的发展，考虑到每个相的原位行为。教育活动包括本科生在加州理工学院和国家实验室的研究经验；新课程开发，使加州理工学院的材料科学课程更加平衡；以及在教学中采用先进的计算工具，特别是在研究和教育中使用互联网。具有复杂微观结构或多相结构的材料（复合材料）正变得越来越普遍，特别是在航空航天结构和发动机部件等关键应用中。这些复杂材料的成功应用需要了解每个相的原位共变形。然而，这种变形尚未被系统地研究过。为了开发更复杂的微观力学模型并最终改进复合材料的设计，需要包含复合材料的每个相的多尺度变形行为的详细信息

9985264UstundagThis grant presents a detailed CAREER plan that will employ the latest improvements in neutron and X-ray diffraction instruments to characterize the response of individual phases in a composite to applied loading. Model specimens are prepared that are essentially fibrous composites, and progress from a single fiber to an array of fibers and finally to a three-dimensional stacking of fibers approaching the geometry of "real" composites. The specimens are loaded under an X-ray or neutron beam to measure the strain response of each phase. By varying applied stress and temperature, crucial phenomena is determined, such as in-situ yield stress, matrix or fiber cracking, interface debonding, evolution of load sharing due to creep in one phase, interactions between neighboring fibers, and evolution of damage zones. The overall macroscopic response of the composite is measured via strain gauges or extensometers attached to its surface. The main goal is to provide reliable mechanical behavior data that will lead to development of constitutive equations that take into account the in-situ behavior of each phase. The education activities include research experience for undergraduate students at Caltech and in national laboratories; new course development that leads to a more balanced Materials Science curriculum at Caltech; and adaptation of advanced computational tools in teaching, especially the use of the Internet in research and education. %%%Materials with complicated microstructures or multiple phases (composites) are becoming increasingly prevalent, especially in critical applications such as aerospace structures and engine components. The successful application of these complex materials requires knowledge about the in-situ, co-deformation of each phase. This deformation, however, has not been investigated systematically. In order to develop more sophisticated micromechanics models and to eventually improve the design of composites, detailed information on multiscale deformation behavior of each phase comprising a composite is needed.***