Nanoscale Toughening Mechanisms Of Ultra High Temperature Novel Hfb2 Based Multiphase Ceramics

Abstract

During return of spacecraft they endure very high temperatures (3000°F), few materials can withstand temperatures this high along with additional loads of the spacecraft. Reinforced carbon-carbon (RCC) material system is used as Thermal Protection System (TPS) which is made of laminated graphite rayon-phenolic epoxy, which need to sustain extreme heat. However, these materials are very prone to premature degradation due to oxidation. Silicon Carbide (SiC) and Hafnium Diboride (HfB2) are candidate materials for TPS but, they inherently lack the required toughness for such applications. This research is carried out in two stages, first is to study the individual properties of SiC and HfB2 at high temperatures and different crack lengths at the center, second is to combine the two materials in a layered structure and evaluate the properties thus changed due to their composite form. The study is carried out using Molecular Dynamics Simulation (MDS) techniques and a considerable improvement in the tensile strength of the Nano-composite is found. This study investigates Silicon Carbide (SiC) and Hafnium Diboride (HfB2) Nano-composites layers as an alternative to RCC. Behavior of these materials have been studied using Molecular Dynamics Simulation (MDS). As individual materials they are susceptible to low toughness, but study shows that their Nano-composite form in suggested configurations can improve their toughness characteristics and retain it at high temperatures making them suitable for TPS.