Dissertation

Multi-Field Modelling of Composite Batteries

Salgado, Rui Martim Lopes Busto

2021

Overview

The main purpose of this work is to develop a tool to aid the design of a next generation multifunctional material system commonly referred to as a structural battery or a composite battery. The main goal is to develop analysis models to study and predict their material, structural and system behavior involving coupled fields phenomena occurring at several length scales. A numerical finite element framework to study the multi-physics evolution at a component/macro scale is proposed and focused on the fracture and damage characterization at the engineering fracture mechanics length scale. A modeling technique of loosely coupling temperature, chemical, or other relevant fields with the displacement, (elastic) strain and stress fields is proposed. On the other hand, a strong coupling between the elasticity fields and macroscopic crack evolution is considered. To capture relevant cracking phenomena such as crack initiation, propagation, and deflection, a phase field model for brittle fracture was implemented.The numerical analyses presented were validated by studying state-of-the-art benchmark problems usually encountered in other works concerned with phase field models for brittle fracture. A good agreement with benchmark results taken from the literature is obtained. A comparison between different modeling techniques is presented focusing on their effect on maximum strength, structural stiffness, crack propagation and load drop during collapse. It was concluded that the model is able to capture crack phenomena such as initiation, propagation, and crack irreversibility and stiffness recovery due to tension-compression load reversal.A phase-field fracture model loosely coupled with simple diffusion problems obeying Laplace’s equation was also considered. A numerical analysis for a coupled fracture and transient heat conduction single-edge notched tension specimen with prescribed temperature and insulation showed that physically accurate results can be obtained by considering loose coupling of fracture problems with thermal fields. Moreover, it was also highlighted that the presence of temperature gradients significantly influences the structural response of a material.An experimental mechanical characterization of a new composite battery is also addressed in this thesis. A three point bending test was performed until the point of structural collapse. The material system tested has been recently patented by the MatER - Materials for Energy Research-Group - and has resulted from a joint effort by the Physics and Mechanical departments at FEUP, and researchers at INEGI. The design is based on a all-solid-state glass electrolyte-based sodium battery with auto and thermal charge capability as the electrochemical harvesting material, and a carbon fibre thin-ply quasi-isotropic laminate as the structural element. The multi-functional (structural and energy storage) beam battery showed very promis-ing results for system-level mass reduction. Furthermore, by introducing multifunctionality, the failure mode obtained for the beam changed from a progressive load and stiffness degradation to a pseudo-ductile structural behavior improving the post-peak bending response of traditional tubular beams.

• Publisher: ProQuest Dissertations & Theses
• Subject: Boundary conditions / Carbon / Composite materials / Crack propagation / Electric vehicles / Electrolytes / Energy storage / Fracture mechanics / Heat conductivity / Heat transfer / Industrial engineering / Lithic / Load / Manufacturing / Market shares / Materials science / Mathematics / Mechanics / Shear tests / Solids / Tension tests / Thermodynamics / Transportation
• ISBN: 9798381548501