With prolific advances in science and technology, there is a constant need for state-of-the-art materials that are strong, tough, light weight, yet thermally and chemically stable. In the recent past, geopolymer has attained much consideration due to numerous benefits over common matrix materials. Geopolymer is an inorganic polymeric material with good adhesive, thermal and chemical properties. It has manifold applications like - fire resistant materials, binders, composites for infrastructure repair/strengthening, radioactive waste containment, furnace molds etc. It can also be used as an alternative to traditional Ordinary Portland Cement (OPC) because of higher sustainability as compared to OPC. Fillers such as carbon fibers, alumina, chamotte, granite, organic/biological fibers are commonly added to geopolymers for enhanced mechanical properties. Due to this wide range of possibility, many experimental studies have been conducted. Although, these studies have brought significant breakthroughs into the science and technology of geopolymer composites, the determinants of strength and toughness are still not fully understood. Consequently, lack of a fundamental understanding has slowed the discovery of advanced geopolymer-based composites. Thus, the research objective is to shed light on the elasto-plastic behavior of geopolymer composites using theoretical and computational nonlinear micro-mechanics. We focus on particulate metakaolin based composites with granite or chamotte fillers. An analytical upscaling model was developed to predict the homogenized elastic response and the uniaxial yield strength of the two phase composite as a function of volume fraction of reinforcement. The filler was modeled as a Von Mises material whereas the geopolymer matrix was considered to be a cohesive frictional material, to account for its high strength in compression over tension. To represent the exact geometry of the composite, finite element mesh was generated using an object oriented FEM software, OOF2D. Essentially, a uniaxial tensile test was simulated in ABAQUS with the OOF2D mesh as input whilst the same material definitions as that of the analytical model were used. The stress-strain curves obtained from the simulations reflected the elasto-plastic response of the geopolymer composite. From both the analytical and computational model, it was found that 50% fillers by volume increased the yield strength by almost 2 times. These results conform to existing literature and thus accurately represent the homogenized response of geopolymer composites. Hence, this study opens new avenues in geopolymer research by substantially reducing the experimental time and cost, meanwhile enabling us to study a wider range of filler materials.
|Published - Jun 7 2017