CAREER: In-Situ Characterization of Materials

9985264 UstundagThis赠款提出了一个详细的职业生涯计划，将采用中子和X射线衍射仪器的最新改进，以表征复合材料中各个阶段对应用负载的响应。制备基本上是纤维复合材料的模型试样，并且从单个纤维进展到纤维阵列，最后进展到接近“真实的”复合材料的几何形状的纤维的三维堆叠。在X射线或中子束下加载试样以测量每个相的应变响应。通过改变施加的应力和温度，确定关键的现象，如原位屈服应力，基体或纤维开裂，界面脱粘，由于蠕变在一个阶段，相邻纤维之间的相互作用，和损伤区的演变的负载分配的演变。复合材料的整体宏观响应通过连接到其表面的应变计或引伸计测量。其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，考虑到每个阶段的原位行为。教育活动包括为加州理工学院和国家实验室的本科生提供研究经验;新课程开发，使加州理工学院的材料科学课程更加平衡;以及在教学中适应先进的计算工具，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（复合材料）的材料越来越普遍，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，这种变形还没有被系统地研究。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，需要关于组成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.***