Mr Joe Morgan
Postgraduate Researcher (Metamaterials CDT 2015)
Joe graduated from the University of Exeter in 2015 with a class I master’s degree in mechanical engineering (MEng). During his undergraduate Joe wrote two dissertations; one for his third year and one for his fourth year. His third year dissertation looked at the addition of fullerenes to polymers using electrospinning as a manufacturing method. This project took interest in the mechanical properties of the resulting composites. Joe's final year disseratation was an investigation into the effects of wind induced vibrations on long span bridges. The project used the Humber Bridge in Hull as a case study. The project largely involved using large eddy modelling and detached eddy modelling in the program OpenFOAM to model instantaneous turbulent structures across a bridge deck section.
Currently Joe is working with Prof. Monica Craciun, Prof. Steve Eichhorn (Univerisity of Bristol) and Prof. Yanqiu Zhu on his PhD project; Lightweight, Transparent, and Sustainable Metamaterials. The project looks at combining cellulose nanocrystals and graphene to produce composites and devices.
Cellulose nanocrystals (CNCs) and graphene both have desirable properties as nanomaterials. The nano-sized, rod shaped crystallites of cellulose offer high aspect ratios, high mechanical strength, a simple manufacturing process and evidence of self-assembly in certain applications. Graphene has been demonstrated to have the highest recorded Young’s modulus, high aspect ratios, and unusual and novel electronic properties. These materials have found a wide array of applications, both individually and combined, including: material coatings, films, electronic components and reinforcement agents in composites. Despite the usefulness and prevalence of these two materials in modern research, little work has investigated the interaction and interfacial properties of these two materials at the nanoscale.
In this work, we aim to characterize the interfacial strength of the two materials and determine how this interaction changes when a tensile load is applied. It is hoped that this work can be used to explain failure mechanisms and limits of the aforementioned applications.
Four sample types are investigated: a monolayer film of CNCs, a monolayer of graphene, a bilayer of graphene covered with a CNC film, and a bilayer of CNCs covered with graphene. Each of the samples, loaded on the surface of an epoxy resin beam, is subjected to a four-point bending test. At set intervals of strain a Raman spectrum of the samples is taken with a focus on the characteristic 1095 cm-1 band for cellulose and the 2D band for graphene. As strain is applied, these characteristic bands shift in position at a given rate. It has been shown in previous research that this rate of band shift per strain (cm-1/%) can be correlated to the stress in a material. By comparing the rates of band shift in the monolayers against the rates of shift in the bilayers, one can determine how combining the two materials affects the stress at the nanoscale. This information can be used to determine stress transfer properties and hence interfacial bonding strength.