Strong and Multifunctional Geopolymer Composites: A Multi-Scale Study

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This award supports fundamental research to provide new knowledge that paves the way for a systematic design of advanced geopolymer composites. Geopolymer composites are a new class of amorphous polymeric hybrids with attractive attributes that have the potential to drastically change the way composites materials are synthesized. Geopolymer-based hybrids are relevant to a vast array of fields such as civil, aerospace, mechanical, and biomedical engineering. However, established relationships between performance, chemistry, and composition are lacking. As a consequence, the widespread application of geopolymer-based materials has been impeded, despite their high potential. The integration of cutting-edge experiments with advanced computational modeling will accelerate the discovery of high-performance multifunctional structural composites. Geopolymer composites have been theorized for many interdisciplinary applications including enhanced-performance construction materials, passive cooling systems for buildings, biomaterials for bone repair, membranes for clean energy generation, and sound insulation systems. Therefore, results from this research will benefit the U. S. economy and society, and spur materials discovery. This research involves the collaboration between three institutions and across disciplines including nanoscience, solid mechanics, and materials science. Comprehensive outreach activities will be implemented in collaboration with local high schools to contribute to raising the next generation of materials scientists. Therefore, the multi-disciplinary approach will help broaden participation of underrepresented groups in research and positively impact engineering education.Geopolymers are amorphous inorganic polymers that result from the reaction between an aluminosilicate source and an alkali metal hydroxide or silicate solution. Despite a wealth of studies, the origin of the strength of geopolymer composites is not fully understood. This research is to fill the knowledge gap by connecting the effective response to the micro- and nano- constituents based on continuum and computational micromechanics integrated with nanoscale mechanical characterization methods. The research team will formulate a theoretical micromechanics model to predict the macroscopic constitutive behavior, articulate new variational solutions using the modified secant approach within nonlinear homogenization theory, build a periodic microfield finite element model that accounts for multiaxial loading cases as well as morphological features, test the hypothesis that nano-porosity is the driving factor controlling the macroscopic mechanical response, validate the theoretical models by carrying out nano- and macro-scale mechanical tests on microsphere-reinforced potassium-based geopolymer composites, and establish correlations between nano- and micro-scale characteristics and the macroscopic behavior.