University home > Advanced Composites Centre for Innovation and Science > Research > Multifunctional composites and novel microstructures
Advanced composites provide unique opportunities to create structural materials with added functionality e.g. for sensing, or self-repair, and new material architectures incorporating novel fibres and nanomaterials. Select from the options below for an overview of work undertaken in ACCIS under this theme.
The properties of composite materials can be tailored through microstructural design at different length scales such as the micro- and nano-structural level. At the micro-structural level, our novel approach creates microstructures with controlled inhomogeneous reinforcement distributions. These microstructures effectively contain more than one structural hierarchy. This has the potential to create whole new classes of composite materials with superior single properties and property combinations. Research also involves tailoring the nano-structures of micro-wires/ribbons for macro-composites. A network distribution of TiB whisker within Ti matrix is shown right.
With recent advances in nanotechnology, various nano-scaled materials are becoming increasingly available. Motivated by their unique properties, researches into the development of nanomaterials and their composites (so-called nanocomposites) with specific engineering applications are being actively pursued, these include: Carbon nanotube fibres and their nanocomposites (Dr. Rahatekar); Nanocomposites Coatings for CFRP Composites (Dr. H-X Peng); Nanofibres and nanocomposites for biomedical applications (Drs. Rahatekar and Su); Modelling and design of nanoinclusions (Prof. Scarpa); Clay nanocomposites (Dr. van Duijneveldt); Dispersion and macro-scale properties of nanocomposites (Prof. Geoff Allen).
Auxetic solids expand in all directions when pulled in only one, therefore exhibiting a negative Poisson’s ratio. We are developing new concepts for composite materials, foams and elastomers with auxetic characteristics for aerospace, maritime and ergonomics applications. The use of smart material technologies and negative Poisson’s ratio solids has also led to the development of smart auxetics for active sound management, vibroacoustics and structural health monitoring.
Mechanical and electromagnetic design Increasing importance is currently placed on developing cellular structures and honeycombs to design microwave absorbers for electromagnetic compatibility applications. Usually the electromagnetic design of the materials is kept separate from the mechanical one. We develop, model and prototype honeycomb topologies for sandwich panels, Salisbury screens and general microwave absorbers in a multidomain optimisation framework. Design and modelling is performed using analytical, finite element and finite difference time domain simulations using optimisation methods, like differential evolution. We also design honeycomb topologies with embedded sensing and actuation to provide cores for novel sandwich panels, structural health monitoring and active microwave applications.
Researchers in the CVD Diamond Film Lab based in the School of Chemistry are investigating ways to make diamond fibre reinforced composites. The diamond fibres are made by coating thin (100 mm diameter) tungsten wires with a uniform coating of polycrystalline diamond using hot filament chemical vapour deposition. The diamond-coated wires are extremely stiff and rigid, and can be embedded into a matrix material (such as a metal or plastic) to make a stiff but lightweight composite material with anisotropic properties. Such materials may have applications in the aerospace industry.
Further information: Bristol University CVD diamond group
We are a multi-disciplinary materials chemistry research group, exploring the design principles and applications of novel functional materials. There is a strong focus on ionic self-assembly and the design, synthesis and application of electroactive aniline-based oligomers and related porous conjugated materials in the group. Active research connections exist with the BCFN, ACCIS (Weaver/Bond/Rossiter), as well as with the Farscope Robotics CDT (Rossiter), with current projects spanning soft actuators and 3D printing of functional materials.
Progress in new types of materials will fuel the inventive revolution in the next 20 years. Technology is driven not only by applications but advances in technology itself which opens new possibilities for application. It is important to step away from the mindset which separates actuators, sensors, controllers and power generators. It would be better to consider a continuum where at one end these elements are quite separate (the current state of the art) and at the other extreme one can imagine the fusion of these capabilities embodied in a new ‘composite’smart material (the goal). Much of today’s engineering employs the use of rigid structures. However, the advent of smart materials (such as artificial muscles, undulating swimming fins and smart surfaces) which are soft or semi-rigid offers the prospect for a step-change in the way we use and make the material world around us. New smart materials will insinuate themselves into every aspect of technology as is the case of electronics today. At the Bristol Robotics Laboratory (BRL) we want to exploit such novel ideas in a new generation of robots and although the technology is in its infancy we are keen to build devices which are pliant and will require different approaches to their control; robots can be much more than 19th century mechanical engineering with 21st century electronics ‘stuck on the top’.
Further information: Bristol Robotics Laboratory
Composite materials have been increasingly used in biomedical applications. In orthopaedics, current implants utilising polymers (PE); metals (CoCr) and ceramics (Al2O3 or ZrO2) are not without problems. Growing concerns regarding the wear particles of polymers, increased ion release of metals and fracture of ceramics call for tough, strong and lubricating composite materials that combine the advantages of individual components. In dentistry, aesthetic ceramic/polymer composite materials with superior performance have become increasingly attractive. We have been exploring the fabrication and application of ceramic/metal, metal/polymer and ceramic/polymer composites with aligned, graded and co-continuous phase structure for load-bearing orthopaedic and dental prosthesis and implants. Different fabrication processes, including freeze casting, rapid prototyping, and direct foaming, have been investigated to produce ceramic or metal preforms with controlled hierarchical structures, followed by infiltration of second phase e.g. polymers or metals to produce biomimetic composites that possess bone, teeth or cartilage-like microstructure and properties.
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