Gangwar, Tarun2021-10-132021-10-132021-08https://hdl.handle.net/11299/224925University of Minnesota Ph.D. dissertation. 2021. Major: Civil Engineering. Advisor: Dominik Schillinger. 1 computer file (PDF); xvii, 224 pages.Hierarchical multiphase systems such as plant structures apply the concept of microheterogeneity repetitively across a hierarchy of well-separated length scales: composite microstructures at a smaller scale form the base materials for new microstructures at the next larger scale. Their complex multiphase hierarchical organization in conjunction with physiological, reproductive, and phylogenetic constraints pose significant challenges for understanding their mechanical behavior. A rational understanding of microstructure interdependencies across hierarchical scales is, therefore, essential to pave the way towards more efficient and sustained tailoring with improved properties, for instance in the context of the targeted breeding of agricultural crops. This thesis aims to develop computationally feasible and accurate multiscale analysis and optimization methods that rationally predict the mechanical behavior and self-adapting mechanisms of multiphase hierarchical systems across multiple scales. We focus on three objectives to accomplish the outlined goal. First, we develop a multiscale modeling approach within the continuum micromechanics framework to predict the macroscale stiffness and strength of multiphase hierarchical materials focusing on a broad class of plant materials. Our approach is supported by microimages and chemical analysis data and extensively validated with the reported experiments in the literature and performed experiments by ourselves in the lab. Second, we integrate results from the continuum micromechanics and topology optimization frontiers to establish rigorous theoretical foundations for an efficient concurrent material and structure optimization framework for multiphase hierarchical systems. The framework accounts for the elastoplastic limit behavior across hierarchical scales, while its computational cost does not explode exponentially with the number of hierarchical scales. Finally, working with plant geneticists, we transfer these concepts to rationalize the biotailoring of cereals for improved lodging resistance. This thesis presents a unique opportunity and foundation concepts for the collaborative research efforts of computational mechanics and plant science in a broader context of the biomechanical tailoring of plants.enMultiscale material modellingConcurrent designContinuum micromechanicsGenetic biotailoringHomogenizationTopology optimizationThesis or Dissertation