CAREER: In-Situ Characterization of Materials

Iowa State University, Ames IA

Investigators

Abstract

9985264 Ustundag This 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. ***