This project proposes to investigate the way the polymeric powders of different shapes and sizes flow, interact and sinter in the Laser Sintering process, through modelling and experimental validation. Laser sintering is part of the additive manufacturing technology, known for its benefits in industries where custom made products, lightweight and complex designs are required. In laser sintering a polymer powder bed is heated to just below its melt temperature. A laser is then focused onto the bed which scans a raster pattern of a single layer of the final part. The bed lowers slightly and a new layer of powder is applied. The process is then repeated until the component is made and the additive layer process is complete. The spreading and compaction of the powder is an important part of the LS process, a non-uniform layer of powder leads to high porosity and weaker bonding between layers and therefore a structure with poor mechanical performance. Similarly, the size and shape of particles can change the sintering process. Larger contact areas between particles lead to a good sintering profile and ultimately to a high density part and good mechanical properties. Surface area of particles, polymer viscosity and surface tension are characteristics which will be considered when modelling the flow and sintering process.

Organic synthesis allows humans to develop molecules that treat disease, efficiently grow crops, power our homes with innovative fuels and lubricants, and develop materials and plastics that are essential for modern life. Redox reactions are an important class of organic transformation where electrons are added or removed from molecules to engender a chemical reaction. This reaction is typically driven by the addition of a reactive redox reagent, which creates large quantities of waste that are often toxic and expensive to dispose of. Electrochemistry is an enabling technology for organic synthesis, as it replaces these reagents by directly transferring electrons at the surface of electrodes submerged in the reaction solution. There are two main advantages to this technique. The first is that lower amounts of waste, or no waste at all, is produced and less energy is needed, providing a more efficient and environmentally sustainable way to conduct redox reactions. The second is that the applied potential, or driving force, can be readily tuned, which provides greater selectivity, new reactivity, higher functional group tolerance and less undesired side-products. While providing efficiency, selectivity and environmental benefits, there are practical challenges associated with electrochemical reactions when compared to standard synthetic organic reactions. The greatest challenge with using the technique is often associated with the set-ups, which can be complex, expensive, are not well suited for parallelisation/reaction development and often lead to poor reproducibility. Thus, there is an urgent need to tackle these problems in order to advance the field. In this project, we will develop new reactor systems to aid each stage of reaction development, namely; discovery, optimisation, dissemination and replication. We will focus on additive manufacturing (3D printing) as an inexpensive, rapid and flexible prototyping tool to generate systems that are accessible, inexpensive and, importantly, highly reproducible for organic synthesis. We will develop new materials, innovative designs, print procedures and optimisation tools for reactors, which will be used in the development of a number of synthetic transformations, for which we have preliminary data, but require new reactor-systems to advance further. We will also conduct fundamental studies to further understand the reproducibility issues that currently plague the use of electrochemistry in synthesis. Specifically, the high-level objectives are to a) invent a screening system for organic electrochemistry, b) solve the reproducibility problem, c) create Super-Cells: the next generation of reactors of organic electrochemistry. This 3D printed approach to organic electrochemistry will increase the speed and ease with which novel organic transformations are developed and reproduced, ensuring electrochemistry can deliver on its potential of highly efficient and sustainable chemical reactions. This project will facilitate wide-spread adoption of the technique in organic synthesis, and deliver fundamental understanding, environmental and economic benefits to industry, academia and society as a whole.

Composites based on continuous fibre prepreg sheet laminates are a mature technology - widely used in the aviation industry for key structural components, However, the future horizon for composite development now lies in providing lightweight thick-section composite parts aimed at replacing metal components predominantly within the automotive sector. High thermal tolerance, thick section composites that are tough and durable could now offer a viable metal replacement technology for an expanding range of sub-chassis applications, particularly wheels, suspension, braking systems gear casings, rotor shrouds and components within the engine compartment. Historically, monolith-type, thick-section parts have typically been made from aluminium or steel, and exceptionally with thermoset composites - but these have fundamental drawbacks when used for thick-section moulding. Thermoplastic discontinuous fibre tapes offer a tantalising alternative to traditional thermosets. Thermoplastic composites (TPC) based on e.g. PEEK and high-performance Nylons have the potential to offer a viable lightweight aluminium replacement option, with superior toughness and fatigue performance - both critical considerations for both automotive and aviation applications. The excellent formability and high flow characteristics mean parts can be produced quickly and cheaply with part counts into the 100,000's, making this class of composites uniquely suited to the volume demanded by the automotive industry, whilst also being capable of being used in thick section mouldings . The recent development of Polyether ether ketone (PEEK) carbon fibre moulding compounds at Exeter showed that this material achieves a bulk modulus of ~40GPa when hot-pressed, which, whilst short of the ~70GPa offered by aluminium, is a marked improvement over previous offerings. Recent advances in manufacturing approach pioneered by the University of Exeter have seen the achievable modulus reliably pushed above 70GPa - directly on par with Aluminium, and, most excitingly, a technique by which controlled, localised orientation might be achieved through the use of pre-consolidated charges, exploiting the high viscosity of the material during manufacture. This technique could revolutionise the TPC sector, allowing the simple manufacture of thick-section components with the optimised design properties previously found only in multiaxial ATL processes. The new "pre-charges" route being proposed, will simplify manufacture, and remove the barriers to rapid volume production, similar to the advent of prepregs and SMC in the 1970's, that made possible the controlled, mass-manufacture of high performance composites in the aviation and automotive industries. A base line improvement in properties together with the removal of manufacturing barriers, could change the current emphasis on thermosets to thermoplastics, which is highly important environmentally. Recycling of most types of thermosets is not commercially viable, despite extensive research into the area. Thermoplastic based systems have the potential to solve the recycling issue, with the ability to melt and re-press components without performance implications greatly improving the recyclability of the material - a characteristic that has long eluded thermoset CFRP's. Moreover, this trait lends itself exceptionally well to in-situ repair and damage healing. The viability of remanufacture and remoulding of composites needs to be established for all of the most common TPC's available. The study will both consider the remanufacture of components (closed loop recycling), and also the viability of 'shape change' with TPC's, i.e. the extent to which materials can be reprocessed like metals through re-melting and reforming multiple times. The future vision is for manufacturers to include recycling/remanufacture instructions as part of standard materials datasheets.

The aim of this proposal is to develop novel high performance, nanocomposite feed materials for Additive Manufacturing (AM). The field of AM, also known also as 3D Printing, has expanded significantly over the last couple of decades across virtually all-industrial sectors due a number of key advantages that traditional manufacturing just cannot offer. These include mass customisation, geometrical complexity, tool-less manufacture and sustainable manufacturing. Among the companies using AM are GE (medical devices, and home appliance parts), Lockheed Martin and Boeing (aerospace and defense), Invisalign (dental devices) and LUXeXcel (lenses for light-emitting diodes, or LEDs). The worldwide revenue from 3D printing is expected to grow from $3.07 billion in 2013 to $12.8 billion by 2018, and exceed $21 billion by 2020, and has a potential of generating an economic impact of $230 billion to $550 billion per year by 2025. While the forecast for AM products is huge this will only be achieved if we can actually manufacture parts with the desired properties. The majority of polymeric AM research is however focused on low glass transition temperature (Tg) polymers such as Polyamide 11, 12 , Polycarbonate and Poly Lactic acid (PLA), due to their good processing characteristics (rheological, thermal and crystallization). For advanced, high value applications in aerospace, telecommunication and defense where harsh environmental conditions often exist (and in some key biomedical application) these low Tg polymers for AM are not acceptable so there is a real need to develop materials for these applications. Whilst a sufficiently high Tg polymer could offer the required high performance, nanocomposites with increased functionalities and potential combinations of properties such as high stiffness, strength, wear and specific thermal, electrical and microwave response can really transform the performance of AM components. The ability to manipulate other properties, such as rheological and thermal performance, by the addition of nanoparticles offers further potential advantages in terms of processing characteristics. This proposal will examine the potential of inorganic fullerene-like (IF) tungsten disulfide (WS2) or IF-WS2 as nanofillers for high value, PAEK (Poly Aryl Ether Ketone) based products made via the AM processes of Selective Laser Sintering (SLS) and Fused Deposition Modelling (FDM). The incorporation of IF particles has been shown to be efficient for improving thermal, mechanical and tribological properties of various thermoplastic polymers, such as polypropylene, nylon-6, poly(phenylene sulfide), poly(ether ether ketone). These nanocomposites were fabricated by simple melt-processing routes without the need for modifiers or surfactants . IF-WS2 have been proven to exhibit extremely high tribological performance in composites to reduce wear and coefficient of friction .These characteristics will also have important processability benefits for AM processes as will their dispersion characteristics which are superior to 1D and 2D nanoparticles. They are also the best shock absorbing cage structures known to mankind. Importantly, they are non-toxic, and thermally stable. We will examine the two main AM processes for producing parts with engineering properties, Selective Laser Sintering (SLS) in which a laser is used to melt and sinter powdered polymer into the final part and Fused Deposition Modelling (FDM) in which a polymer filament is melted in a heated nozzle and deposited in the required pattern to form the part.

High performance fibre-reinforced polymer composites are the current state-of-the-art for lightweight structures and their use is rising exponentially in a wide range of applications from aerospace to sporting goods. They offer outstanding mechanical properties: high strength and stiffness, low weight, and low susceptibility to fatigue and corrosion. The use of high strength, high stiffness materials in fibre form mitigates the tendency for premature brittle failure, enables components to be formed at low or moderate temperatures, and enables anisotropic designs to target the primary load-carrying demands. Fibres are particularly efficient in uniaxial tension but, under compression, composites suffer a range of failures typically associated with fibre micro-buckling or kinking, linked to matrix or interfacial issues; these mechanisms couple in a complicated way at a variety of physical lengthscales. Often, these types of failure determine the practical usage of composites and set design limits well below the expected intrinsic performance of the constituent fibres. On the other hand, new constituents and processes are becoming available that enable the directed assembly of composite structures, controlled across a much wider range of lengthscales than previously possible. In principle, then, composite materials should be redesigned to take advantage of these opportunities to supress or redirect the failure process in compression. Natural materials, such as wood and bone, are fully hierarchical, with precise structural features resolved at every possible magnification. Artificial composites lack this dexterity but can exploit intrinsically superior constituents. The increasing ability to visualise, calculate, and control structures, including with quantitative precision, will allow a new generation of composite materials to be developed. The ambition is to realise the full intrinsic potential of the fibres by designing such hierarchical systems for compression, from first principles, exploiting the latest developments in materials, processing, characterisation, and modelling of mechanistic processes. This programme focusses on the challenge of improving the absolute performance of composites in compression, both to address practical limitations of current materials, and as a demonstration of the value of quantitative hierarchical materials design. Tools and materials developed during this programme will be useful in a range of other contexts. The work will develop and embed structure at every lengthscale from the molecules of the matrix, to the lay-up of final components, using new constituents and new architectures, designed with a new analytical framework. The programme will benefit from a highly creative and interdisciplinary approach amongst the core project term, amplified by contributions from leading international advisors and collaborators. An extensive group of industrial partners will contribute to the project, and help to develop the outputs, building on concept demonstrators designed during the programme. The scientific and technical results will be widely disseminated nationally and internationally, helping to ensure UK leadership in this key field.