A new project led by the University of Southampton will explore the use of composites in aerostructures and seek to highlight the limitations in current certification procedures.

Backed by an EPSRC grant of £6.9m, the research will focus on more structurally efficient and lightweight airframes. In doing so, the team hopes to challenge existing aerospace norms and seek step-changes that the regimented certification process may be preventing. By driving reduced weight, cost and development cycles, the researchers are aiming to lay the foundations for the aviation of the future, where fuel efficiency and electric/hybrid propulsion are expected to come to the fore.
“This funding is essential to enable continued growth of the UK aerospace industry and take economic benefits from the opportunities inherent in the move towards more sustainable aviation, as it fills a knowledge gap, where there is no equivalent capability in the UK or internationally,” said lead researcher Ole Thomsen, professor of structures and materials at the University of Southampton.
“Using world-class expertise, this programme grant from EPSRC will enhance the UK position in the technical revolution that embraces new materials and processes, by addressing an urgent need in aerostructures design.”
Titled ‘Certification for Design: Reshaping the Testing Pyramid (CerTest)’, the research programme will take a completely new approach to component development. The current certification regime takes a so-called ‘building block’ or ‘testing pyramid’ approach, examining components at (i) Coupon, (ii) Structural detail, (iii) Component, and (iv) Sub-structure or full structure level. As the cost and complexity of testing increases through the levels, the vast majority of testing takes place at the ‘Coupon’ stage. The underlying assumption is that the material properties derived from lower levels can be used to extrapolate the requirements for higher component complexity. But the researchers claim this is not necessarily the case.
“At best, this leads to conservative, over-constrained design,” according to the grant application. “At worst, there is risk that potentially unsafe scenarios can develop where combinations of weakening events cascade into premature failure.”
“There is increasing awareness that, in its current form, the ‘building block’ approach prevents the innovative use of composites, and consequently that the potential benefits of using advanced composites in terms of lightweighting and efficiency cannot be fully realised under current certification and regulatory procedures.”
In pursuit of its goals, the project will implement virtual testing and advanced data-rich experimentation of aerostructure components and substructures. Academic project partners include the University of Bristol, University of Bath and the University of Exeter, while industry support comes via Airbus, BAE Systems, Rolls-Royce, GKN Aerospace, the Alan Turing Institute, CFMS and the National Composites Centre.
Often people seem to use advanced to relate to any composite material – even glue and glass type so it not quite clear what is being looked at. Metal or thermoplastic matrix composites offer more opportunities in terms of manufacturing improving the material (usually via the stress state) – as indeed coupon testing may even be optimistic in material behaviour (which would be more worrying for design!) – and so too for layered or hybrid composites.
So it would have been interesting to see if they are looking at exciting materials that are truly advanced – including, also, homogeneous composites (such as SiC/SiC)
SiC/SiC is certainly beginning to be used in gas turbine engines
Good to hear.
I have seen that people were looking at SiC/SiC for gas turbines but was not aware that they were using them.
I think that it is an important technology with high impact for, also, energy storage and for nuclear power – so would be great if they are including this in the study.
However the manufacturing route, for these is a major issue – for example the melt infiltration manufacturing route usually ends up with excess silicon – which is not good for oxidation resistance and creep.
Rolls-Royce has started to run trials fairly recently.