Atomic scale analysis of fracture in 3C-SiC
Date
2021
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
Ceramics are a promising candidate for application in different engineering fields ranging from dentistry to the spacecraft industry. In recent years, Silicon Carbide (SiC) has become the cornerstone of material research because of its potential to resist high-temperature, impact load, chemical reaction, thermal shock, etc. Instead of prominent tensile and compressive strength, the fracture toughness of SiC is significantly low due to the brittle nature of the crack progression. In this thesis, we applied classical molecular dynamics simulation to exploit the atomistic origin of the failure mechanisms in bulk 3C-SiC, porous 3C-SiC, and the SiC/SiC composite. Using a set of well-defined atomic interactions, we investigated the fracture properties and crack propagation path. Considering accuracy and the computational expense, we applied Stillinger-Weber interatomic potential for large-scale simulations containing millions of atoms. In a bulk 3C-SiC, we studied the effect of crystal structure on the ideal tensile strength and toughness. We reported a strong anisotropy in mechanical behavior governed by the disparity in bond force distribution for different crystallography of the particles. The non-uniform applied forces across the cross-section influence the crack propagation and fracture toughness. When the material is discontinuous, the effect of the anisotropy rules the overall mechanical behavior. In the investigation of porous SiC, we demonstrated a toughening mechanism infused by crack-pore interaction. We delved into the effect of atomic configuration, crack length, pore size, and the distance of pore from the crack tip to understand the factors that control the counter-intuitive strengthening event. We reported a six-times tougher SiC when a crack encounters a pore in its path. Finally, we modeled a carbide composite with 3C-SiC [111] as a matrix and 3C-SiC [100] nanowire as the reinforcing inclusion. We intend to explore the impression of a second material on the fracture properties. Numerical optimization is applied to design a naturalistic fiber-matrix interface. We studied the effect of inclusion size and the interfacial atomic density in the debonding and fracture process. To illustrate our findings, we presented power-law equations for quantitative predictions of the strength and toughness of the composite.
Description
Keywords
Anisotropy, Crystallography, Fracture, Molecular Dynamics, Renucleation, Toughness