Eudora Yeo

Functionalization and Dispersion of Carbon Nanomaterials Using an Environmentally Friendly Ultrasonicated Ozonolysis Process

Functionalization of carbon nanomaterials is often a critical step that facilitates their integration into larger material systems and devices. In the as-received form, carbon nanomaterials, such as carbon nanotubes (CNTs) or graphene nanoplatelets (GNPs), may contain large agglomerates. Both agglomerates and impurities will diminish the benefits of the unique electrical and mechanical properties offered when CNTs or GNPs are incorporated into polymers or composite material systems. Whilst a variety of methods exist to functionalize carbon nanomaterials and to create stable dispersions, many the processes use harsh chemicals, organic solvents, or surfactants, which are environmentally unfriendly and may increase the processing burden when isolating the nanomaterials for subsequent use. The current research details the use of an alternative, environmentally friendly technique for functionalizing CNTs and GNPs. It produces stable, aqueous dispersions free of harmful chemicals. Both CNTs and GNPs can be added to water at concentrations up to 5 g/L and can be recirculated through a high-powered ultrasonic cell. The simultaneous injection of ozone into the cell progressively oxidizes the carbon nanomaterials, and the combined ultrasonication breaks down agglomerates and immediately exposes fresh material for functionalization. The prepared dispersions are ideally suited for the deposition of thin films onto solid substrates using electrophoretic deposition (EPD). CNTs and GNPs from the aqueous dispersions can be readily used to coat carbon- and glass-reinforcing fibers using EPD for the preparation of hierarchical composite materials.

Effect of Humidity and Thermal Cycling on Carbon-Epoxy Skin/Aramid Honeycomb Structure

Many modern military aircraft are constructed from composite and bonded structure, such as thin carbon-epoxy laminate bonded to Kevlar® and Nomex® honeycomb. Operation of these platforms in Australian and global conditions will subject the structure to potentially high levels of humidity, extremes in temperature, and for maritime operations, exposure to salt spray conditions. The thin composite laminate is likely to rapidly absorb moisture in a humid environment and enable permeation of moisture into the adhesive and core. In addition to the chemical influence of moisture on the composite structure, the moisture trapped in the honeycomb structure may freeze and expand with changes in altitude during operations or simply due to daily temperature fluctuations at the resident airbase. The combination of moisture ingress in the honeycomb structure and thermal cycling may lead to deteriorated strength of the honeycomb panels over time that would not be observed for long term humid exposure alone. Long term salt water absorption may also have an adverse effect on composites structures. This study investigates the effects of humid environments and thermal cycling on the mechanical properties of composite and honeycomb structures.