Bioinspired Layered Geopolymer Composites (Ph.D. Defense)
Anass Harmal will be presenting his Ph.D. Defense on May 23rd at 9:00am. Please join in KH 111A or via Zoom (https://wpi.zoom.us/j/95256665763
Defense topic: Bioinspired Layered Geopolymer Composites
Geopolymer has been at the forefront of climate conscious construction materials' research. This is a result of the material's ability to develop similar strength to Ordinary Portland Cement with lower levels of emissions. Geopolymer is, however, limited by several factors: The complexity of the geopolymerization reaction, no effective control over the flow and setting/curing time, and very low toughness.
The presented work focuses on augmenting geopolymer toughness by orders of magnitude without compromising strength. To achieve this objective, biological layered composites, such as nacre and bone, are used as inspiration for the proposed design. Specifically, a brick-and-mortar structure is considered where geopolymer is the brick phase while various polymers are the mortar phase. First, this work focuses on exploring the synthesis of bioinspired layered geopolymer composites, reporting the effect of the soft phase stiffness on the performance of the composites, and uncovering underlying toughening mechanisms at the macro and micro scales. Second, important morphological parameters, identified in biological layered composites, are utilized to showcase their effect on the mechanical behavior and toughening mechanisms of bioinspired layered geopolymer composites. Third, given the vast design space of the synthesized composites, simulation is considered to explore this design space effectively. A simulation based on Lattice Spring Modeling (LSM) is formulated and used to explore the effect of the stiffness and strength of the soft phase and interface on the fracture of bioinspired layered geopolymer composites.
Results from this design approach three orders of magnitude in toughness augmentation while preserving or increasing strength. The present design approach also presents composites with strength and toughness levels higher than both their constituents.