The School for Science and Math at Vanderbilt
Lesa Brown, Ph.D.
During the first few years of my graduate studies, I had the opportunity to mentor a number of undergraduate and high school research assistants. The mentoring and teaching relationships that I developed with these students in the lab were what sparked my interest in teaching in the STEM disciplines. The students often had many questions regarding the year I spent in industry before returning to graduate school, and I quickly realized there was a disconnect between what they were taught in the classroom versus what they thought they would be doing in industry or research. I saw first-hand how important hands-on research and engineering experiences were for high school students in order to better prepare them for what to expect during the path to an engineering career. These experiences encouraged the development of critical thinking and problem-solving skills and introduced the idea that real-word problems don’t always have a single, “right” solution. This embodies what I hope to bring to the School for Science and Math – interactive and hands-on engineering activities that help students link engineering theory with real world applications.
My graduate studies focused on investigating the effects of carbon nanofiber (CNF) clustering on the chemo-mechanical behavior of cement pastes subjected to aggressive environments. While CNFs have the potential to improve cement paste durability and long-term service life due to decreased crack propagation and increased cohesion of the paste, the fibers have proven difficult to effectively disperse at the nanoscale. My dissertation research utilized a multi-scale experimental approach to examine the attributes of the cement pastes with CNFs from the micro- to the macroscale during exposure to aggressive environments. The approach integrated microstructural and chemical studies with nano/micromechanical studies and traditional static and dynamic mechanical testing (i.e., three-point bending, uniaxial compression, and pulse velocity measurements). This provided a fundamental dataset that was used to develop a homogenization model which captured changes in the mechanical properties at the microscale due to CNF clustering and aggressive environments and upscaled those changes to the macroscale. It is hoped that a better understanding of the behavior of CNF clustering during exposure to aggressive environments may provide for improvements in dispersion methods and allow CNF reinforced cementitious materials to reach their full potential.
- Brown, L and Sanchez, F. Influence of carbon nanofiber clustering on the chemo-mechanical behavior of cement pastes. Cement and Concrete Composites. 2016; 65:101-9.
- Stephens, C, Brown, L and Sanchez, F. Quantification of the re-agglomeration of carbon nanofiber aqueous dispersion in cement pastes and effect on the early age flexural response. Carbon. 2016; 107: 482-500.
- Brown, L, Allison, P and Sanchez, F. A hybrid nanoindentation and homogenization method for the mechanical properties of heterogeneous decalcified cement pastes. (To be submitted, 2016).
- Brown, L, Allison, P and Sanchez, F. Micromechanical behavior and multiphase homogenization analysis of cement pastes with carbon nanofiber clustering. (To be submitted, 2016).
- Brown, L and Sanchez, F. A Nanoindentation Study of Portland Cement Pastes Exposed to a Decalcifying Environment. In: Sobolev, K. and Shah, S. (eds.). Nanotechnology in Construction: Proceedings of NICOM5. Cham: Springer International Publishing. 2015; p. 65-70.
- Brown, L, Sanchez, F, Kosson, D, Arnold, J. Performance of carbon nanofiber-cement composites subjected to accelerated decalcification. International RILEM Workshop on long-term performance of cementitious barriers and reinforced concrete in nuclear power plants and radioactive waste storage and disposal (NUCPERF), EPJ Web of Conferences, 56, 02005, 2013. doi: http://dx.doi.org/10.1051/epjconf/20135602005