Standing the test of time

standing-the-test-of-time
standing-the-test-of-time

Pierangelo Campagna, Exova's technical director for polymers and composites, looks at how the company is anticipating and meeting future demand for composites in the global aerospace sector.

Pierangelo Campagna, Exova’s technical director for polymers and composites, looks at how the company is anticipating and meeting future demand for composites in the global aerospace sector.

Widely quoted figures estimate that the market for aerospace composites will see an average compound annual growth rate (CAGR) of 13% which will mean an increase in the value of the market from $2.1 billion back in 2011 to $6.3 billion in 2020.
As one of the world’s leading independent testing organisations, we are facing the challenge to simultaneously build our own capacity and capability in terms of equipment, people and approvals. We have invested heavily in our global laboratories to ensure we stay at the forefront of this testing, with commitments to fields including dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and fatigue testing, with test frame investments in labs including Toulouse. Our Bridgwater laboratory has been testing polymer-based composites materials for more than 10 years, and in recent years it has entered fatigue testing capability with the acquisition of three servo hydraulic test frames in response to customer demand. Exova Bridgwater, which carries out work for aerospace primes including Rolls- Royce, Airbus and GKN Aerospace, was then awarded UKAS accreditation for a range of composite and metallic international standards. It was also one of the first facilities in the world to hold both metallic and composite testing approval from Nadcap. Looking back to our first forays into the sector, we acquired an important laboratory from Saab which had been instrumental in carrying out early testing work for the Grippen aircraft – one of the most important early composite projects. From an early stage we have remained qualified and approved by the primes themselves, putting us in a great position to provide services to their supply chain. As a result we have tested everything from wing spars and leading and trailing edge panels to turbine blades, nacelles and, more recently, fuel lines. But as composites are now being used in much more design-critical areas, the requirement for testing has increased to match. Exova’s labs often play a role in the material selection process all the way through to the end product followed by production release and support. Our Swedish lab is now working on methods for recycling composite materials, something which will become increasingly important as production ramps up. More recently we have carried out work on a number of flagship composites projects – the Airbus A350 XWB and the Boeing 787 Dreamliner, two major civil aircraft projects which have really caught the public’s imagination as well as the attention of the industry too, and the Airbus A400M, another composite intensive project, but this time in the military sector. Looking forwards, we fully expect demand on individual projects to increase. These are testing times Exova’s composite analysis for the aerospace sector includes a range of services, from manufacture and production of test panels to repair technology and material qualification. Tests include static and fatigue analysis, fire testing, NDT, environmental conditioning of materials and testing of samples over a wide temperature range. New knowledge is being gained every day as the industry develops more innovative designs. However, the aluminium industry is not sitting back and doing nothing. Composites began to be used in the 1970s, but 40 years later aluminium is clearly still extensively used. Producers are developing aluminium lithium alloys that are lighter and stronger than ever before. Currently one of the main limiting factors for composites is in joining, and there is still concern about using composites in primary structures, limiting their use to external panels as if they are a sheet of metal. The real jump forward will come when the present design concepts will be reversed, i.e. instead of aluminium primary structures and composite body panels, an aircraft will be made with composite primary structures and outer aluminium panels. Exova itself has seen its own fair share of innovation. We have increased the amount of tests we can offer, with compression and bend testing ramped up, but we are also adding new tests required by clients that are much more specific to the composite sector. Particular tests have included open hole compression and filled hole compression; plus open hole tension and filled hole tension to monitor the behaviour of materials and the defects which may occur. Compression-after-impact testing has also become increasingly important, and this is used to simulate impact with different energies and the residual strength of the affected material. This is a test typical to the aerospace sector specifically when the industry began to use composites on structural parts rather than just surface materials. It is important to make sure a structure is completely safe after an impact – a bird strike on an aircraft flying at 500kph creates a lot of energy. Forward thinking We are already being asked to create new tests to simulate a wider range of conditions, for instance temperature and moisture tests to monitor the impact a specific environment has on the properties of a material. Cost is the main factor for prime manufacturers followed by maintenance issues. It is not easy to repair composites compared to traditional aluminium; for instance, following impact damage to a wing structure. The techniques are quite different because of the different physical properties. Other considerations for the future development of composite materials include issues around heat effects and joining techniques. Since welding is not possible with composites, bonding and riveting technologies are the key areas requiring a lot more understanding, research and development. The prime manufacturers are the biggest innovators and we are expecting to see development in the future in terms of nanotechnology, new coating technologies and developments in electrical conductivity in composite materials. As the composite market continues to present the industry with new challenges, we at Exova are excited to be involved in developing innovative testing regimes for now and the long-term future. www.exova.com

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