Not so heavy metal
In Dr Thomas Fiedler's office in the Faculty of Engineering and Built Environment sits a series of neatly arranged blocks. Some look like cubes of silver sponge, others are slim bricks that appear to be made of tiny ball bearings, and the most stunning are pieces of interwoven aluminium threads that form coral-like structures and could easily be converted into contemporary jewellery.
These blocks are lightweight cellular metals and they are the focus of Fiedler's research in the University's Centre for Mass and Thermal Transport in Engineering Materials into the thermal properties of materials.
The Centre, which is directed by Professor Irina Belova, focuses on the development of new models and innovative computational methods for predicting the mass and thermal diffusion behaviour of metals, ceramics, geological materials and composites. It is arguably the leading research group of its kind in Australia, and has gained substantial recognition both nationally and internationally in the area of mass and thermal transport in engineering materials.
Fiedler, a mechanical engineer and member of the team, received the Vice-Chancellor's Award for Research Excellence in 2009 for his investigation of metallic hollow sphere structures (MHSS). These are a new group of cellular metals characterised by easily reproduced geometry, and have consistent mechanic and physical properties.
"Hollow sphere structures have very interesting properties. When you join them together, you have more control over the structure and it is easier to guarantee stability," says Fiedler.
Fiedler has spent the past five years investigating the mechanical and thermal properties of MHSS as a core material in sandwich panels, comparing them to the traditional honeycomb structures used in lightweight construction such as aviation, high-speed trains and boats, where strength is required at minimum weight.
A sandwich structure is a composite where a core material is enclosed in two strong layers that bear most of the applied loads.
The core material acts as a spacer that keeps the outer layers in position by carrying shear stress.
The small sample Fiedler picks up looks like a grey ice cream sandwich, the lightweight porous aluminium enclosed by two thick "biscuit" layers, which are fibre-reinforced polymer.
Sandwich construction has been recognised as a promising concept for the structural design of lightweight transportation. "With MHSS you can have more control over the structure in comparison to other 'random' cellular materials such as metallic sponges and foams," says Fiedler.
Fiedler has concluded that MHSS in sandwich structures shows potential for novel multi-functional applications such as car bodywork, combining energy absorption, comfort and lower weight to create a better driving performance and less fuel consumption.
Cellular metals are effective in damping, acoustic and thermal insulation, as well as being strong. "Honeycombs are great for stiffness and strength, but do not exhibit the other characteristics," Fiedler says.
Being recognised for his research by the Vice-Chancellor was a welcome surprise for Fiedler, who initially considered studying architecture before opting for the more "hands-on" mechanical engineering.
He acknowledges the support of the Centre and its experienced, internationally connected researchers. "Being able to collaborate with researchers around the world means we can do more complex research. The Centre is very well respected."
Find out more about the Centre for Mass and Thermal Transport in Engineering Materials