Setting the standard

The University of Manchester’s National Composites Certification & Evaluation Facility, officially opened this summer, has been set-up to accelerate the standardisation of new material standards and aid the development of new processes. The centre is aiming to go far beyond this however, by establishing itself in a support role for the UK industry with an extensive state-of-the-art laboratory and business development capability.

While the march of new material and process technologies into the wider manufacturing market is anticipated to increase rapidly over the coming decade, the gap between prototype and product can still account for a large part of development. Add to this that many companies and institutions are striving to achieve similar goals as far as new materials, testing and certification are concerned, the NCCEF has been established to provide cohesion to the efforts being undertaken within the industry and serve as a knowledge and resource hub.

Formally opened last June, the NADCAP compliant laboratory has been operational since January 2010 and states its remit as working with companies to understand material performance and behaviour, make the transition from metals to composites, qualify parts for aerospace and other sectors, assess new materials and processes and evaluate 3D structures.

Of these various challenges, the central task is currently to develop a standard qualification for the certification of a range of specific carbon fibre and resin systems in order to remove one of the barriers to entry for companies new to the sector. Currently, the urgency of the environmental and cost issues surrounding the aerospace industry coupled with an anticipated dramatic increase in air travel and the large cost benefits of composite aircraft designs are the main drivers. While the OEMs have the financial muscle and the experience to certify materials themselves, the processes remain proprietary and exclusive only to themselves.

Developing standards for key grades of material saves not only on the huge expense of characterisation and establishing certification procedures, but also simplifies the approval process for suppliers and builds confidence in the markets, facilitating the drastic growth that is required to keep up with the world’s appetite for more efficient transport and power generation systems that drive the materials market.

Gearing up for growth

“The carbon fibre sector is growing at something like 25% a year,” explains NCCEF CEO Andrew Walker. “We believe it is at around 40,000 tonnes a year today and looking at demand we expect this to rise to between 240,000 - 330,000 tonnes in 10 years time, and between 1.5m - 1.8m tonnes by 2023. These figures can be difficult to comprehend but to put it into context, for every factory operational now, the world will need 30 more.

“The automotive sector is also beginning to wake up to mass production, but these companies will want different grades of carbon fibre to the aerospace industry. BMW’s recently announced carbon fibre plant in Washington State for example will produce 4,000 tonnes alone. Basically, after 2012, anything in the car that’s pressurised like hydraulic and brake systems, are all going to be carbon fibre so we’re at the beginning of a parabolic demand curve.

“Wind energy will also undergo a massive change as manufacturers move from glass fibre to carbon fibre blades as larger, more powerful designs enter the market. As with aerospace, most notably the ageing A320 design which needs a lower cost replacement, the improved efficiencies of advanced designs are fuelling new investments. The renewable sector is heading towards progressively larger windmills (up to 300m tall with 80m blades) which can yield up to four times the energy of six smaller turbines, causing people to knock down older wind farms and start over.”

In order to establish standards for key materials that will be strategically important to the industry and its growth, the NCCEF is working with the National Institute for Aviation Research based at Wichita State University and the European Aviation Safety Agency to extend the ‘Composite Materials Handbook 17’. A standard currently used in the American industry and which will be adapted to ensure commonality between these particular grades worldwide.

With its initial £8 million investment, the NCCEF has invested in all aspects of testing and characterisation necessary to examine materials down to the smallest details and produce repeatable results, from mechanical through to non-destructive and chemical evaluation. With its laboratory not only supporting its own research, but also being used by its PhD students and available for commercial and private applications, completely understanding these complex materials will be no simple task. Initially, the centre will be putting five widely-used materials that it believes will be important to the development of new products and businesses under scrutiny, and will use this as the basis for further investigations. These materials include the Advanced Composite Group’s MTM45-1 epoxy prepreg used by many small aerospace manufacturers, but will also look at important materials in other sectors, especially with the UK composite industry’s anticipated growth in renewable and automotive applications.

The complete picture

Its mechanical and impact testing capabilities comprise of eight Instron machines, which will be used to develop standard stress and fatigue testing procedures. Three servo-hydraulic 8802 machines are dedicated to tension and compression testing up to 250kN and in temperatures between -150° - 300°C and a fourth specially built load cell for tension and torsion with very precise measurement and has been proved to be particularly beneficial for creep testing. Three more electro-mechanical machines can perform static testing up to 600kN and an Instron CEAST 9350 offers drop weight impact measurement up to 1,800J complete with an advanced video extensometer with strain gauge correlation. A separate area also houses ballistic testing capabilities, mapping strain and deformation with digital image correlation coming from two 2,000fps high resolution cameras.

The non-destructive testing facilities at the centre will be particularly important in defining the much more unpredictable failure modes that carbon fibre components can exhibit following stress testing. “If you design carbon fibre correctly, it will never fail and the machines should fall apart before the sample.” explains Walker. “However, they are very sensitive to cracks and defects like sharp corners, pores causing premature failure and it’s never linear. Predictability is the largest problem facing those producing and maintaining structural products and small cracks change the behaviour of a whole sample.”

Developing a better understanding of these problems however, the centre has a whole range of technologies available including X-ray tomography for 3D reconstruction of the internal structure of samples, various ultrasonic technologies to identify the size, position and orientation of cracks and shearography and thermography capabilities for rapid identification of changes to material structures. A powerful scanning electron microscope which unconventionally doesn’t require samples to be coated and can analyse samples in just half an hour completes the non-destructive equipment investment, allowing for detailed examination of surface structures at the micro and nano scale.

The third main area of testing, chemical processing, is utilised to investigate the reaction kinetics in order to establish the parameters for correct and repeatable curing, the most important aspect being to achieve consistent material flow to eliminate porosity. This includes differential scanning calorimetry to examine mechanical changes under heating, rheometry to examine viscosity and aid in developing resin formulations and new curing techniques and infrared spectrometry to examine the movement and evolution of specific chemicals within the composite matrix and identify anomalies.

Expanding processing efficiency

Testing and certification is not the full story however. Supporting these activities is a suite of processing equipment to ensure the facilities are well fed and that engineers can react quickly to results being obtained with updated samples. With a dedicated lay-up clean room, autoclave, ovens, pressing equipment and resin transfer moulding facilities, the processing department resembles any contemporary subcontract facility, but with the support of the University of Manchester’s School of Materials, the centre has also taken on the development of new and advanced processes which are attracting interest from companies across the sector.

One particular example being developed by the textiles department is an interpretation of the 3D weaving technology that currently holds great interest for manufacturers due to its speed and versatility and consequently the ability to produce complete, complex components, especially hollow components such as nacelles or UAV fuselages in a single set-up. The current design features two rotating rings allowing 9 axes of motion surrounding a stationary mandrel for simultaneous tow placement in any orientation, although this is an area of manufacture that holds a great deal of potential.

A second project features another machine developed at the centre which uses a 4-axis robot to place glass fibre on a pin board at any orientation to build a 3D structure with a highly specific fibre orientation to improve interlaminar tolerance, and will be of particular benefit for those producing curved structures such as radomes. The centre is also a research partner to Quickstep, an Australian company with an alternative, out-of-autoclave curing method which uses flexible bladders filled with pre-heated oil for rapid, low viscosity processing to ensure void levels lower than 1%. The NCCEF currently houses the only Quickstep machine in the UK and in collaboration with Bolton University, is using the machine to develop new resin formulations suited to rapid manufacture.

With these projects and many more to come, the NCCEF is expected to play a prominent role in the development of new technologies within the UK sector but more important however, will be its role as a cohesive force for those across the whole industry to make the most of the opportunities this rapidly changing market will present.

www.manchester.ac.uk/nccef