MECHANICS OF QUASI-BRITTLE MATERIALS
RESEARCH TOPICS
Multiscale and Multiphysics Modeling
Even with the computational power currently available, the adoption of nano/micro/meso-scale (discrete) approaches become computationally intractable in the case of fine grained materials, such as nano-composites, ceramics, rocks, metallic powders, etc., or in the case of large structures, such as tall buildings, dams, bridges, etc. For this reason there is clearly a need for effective multiscale techniques suitable for upscaling discrete systems. My research group is currently exploring, evaluating the effectiveness, and further extending a variety of multiscale techniques recently developed to bridge atomistic and continuum scales.
The Lattice Discrete Particle Model
Multiscale and Multiphysics Modeling
Even with the computational power currently available, the adoption of nano/micro/meso-scale (discrete) approaches become computationally intractable in the case of fine grained materials, such as nano-composites, ceramics, rocks, metallic powders, etc., or in the case of large structures, such as tall buildings, dams, bridges, etc. For this reason there is clearly a need for effective multiscale techniques suitable for upscaling discrete systems. My research group is currently exploring, evaluating the effectiveness, and further extending a variety of multiscale techniques recently developed to bridge atomistic and continuum scales.
3D Printing of Infrastructure Materials
3D printing aka additive manufacturing is becoming mainstream in many industries. Currently available technologies allow printing engine parts, electronic devices, medical prosthetics, and even clothing, food, and human organs. With 3D printing, the fundamental change in the production processes of objects is associated with a paradigm shift in the way these objects are conceived. 3D printing allows for the design and production of complex shapes that liberate the imaginations of designers, architects, and engineers, opening unexplored possibilities for performance optimization to achieve stronger, tougher, more durable, more esthetically appealing, and more environmentally friendly products, while possibly even reducing costs. One of the many benefits of 3D printing technologies is their versatility and the possibility to adapt the design of the final structure as well as the design if the 3D printing process to local situations and particular needs. In our group, we conduct research focused on 3D printing of infrastructure materials, including concrete, cementitious composites, and sulfur concrete. In addition, we are formulating and validating computational models that simulate the behavior of these materials during the printing process.
Concrete 3D Printing Simulations
Infrastructure Durability
Deterioration induced by Alkali–Silica Reaction (ASR) is reported in many concrete structures all around the world, especially those built in high humidity and warm environments, like dams and offshore structures. The main effect of ASR is a progressive deterioration of concrete stiffness and strength that results from the long-term formation and expansion of ASR gel inducing expansive pressure on the internal structure of concrete. This pressure causes nonuniform deformations that eventually lead to cracking and damage. While the chemical description of the reaction was addressed intensively in the literature, the fracture mechanics associated with the progressive expansion has received little attention due to the lack of models describing concrete internal structure satisfactorily. We work on to fill that gap and to build a comprehensive computational model, considering not only the evolution of temperature, humidity, cement hydration, and ASR in both space and time, but also the physics-based formulations of cracking, creep and shrinkage.
Alkali Silica Reaction Simulation
Composite Materials
Development of energy efficient and environmentally friendly technologies is certainly at the forefront of Engineering of the twenty-first Century. Design of high-strength, light-weight, and corrosion-resistant materials is the key, for example, for the design of energy-saving transportation systems (cars, aircrafts, ships, etc.). We work on the formulation of general triaxial constitutive laws for the simulation of anisotropic elasticity, damage, and failure of quasi-brittle composites, such as carbon-epoxy and glass-epoxy composites. The adopted model (called the Spectral Stiffness Microplane Model) is formulated in the context of the microplane theory and exploits the spectral decomposition of the stiffness matrix to identify orthogonal strain modes at the microplane level. Future extensions of this work will take into account the visco-elastic, rate- and temperature-dependent character of these materials in order to be able to simulate the behavior of mechanical components under high impulsive loading conditions and in extreme environments.
Spectral Microplane Theory
Wood Mechanics and Structures
Rising global emission have led to a renewed popularity of timber in building design. However, there remains a gap in understanding the mechanical behavior of wood, particularly at the scale currently seen in mass timber structures (e.g. greater than six stories). Whilst wood presents a sustainable alternative to concrete and steel, further research is necessary to successfully utilize this material. Our work therefore focuses on novel simulation methods for wood mechanics. We are developing a lattice model to simulate the microstructure of timber using curved beam elements, which allows for representation of the cellular nature of this material without undue computational costs. We are also working on a robust prediction model for wood creep and its resulting effects in full-scale structures. Initial efforts saw the foundation of a database of long-term creep tests, necessary for the verification of such a prediction-based model. Current research is being done to expand this database to include transient moisture effects and orthotropic behavior. Future work has also been laid out to model creep in laminated timber, as seen in mass timber technologies such as glulam and cross-laminated timber (CLT).