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Aerospace Leads the Way in Composite Use

13 August 2004

Industry report suggests that the challenge for composite development in aerospace is based on finding a good compromise between performance and cost.

One market study estimated that 2000 tons of finished composite parts, with a value of $760 million, were produced for the European aerospace industry in the year 2000, and this is set to grow substantially, spearheaded by projects such as Boeing’s 7E7.

These findings form part of a third in a series of reports based on the collated findings of the ten COMPOSIT research clusters with one report for each of the aerospace, automotive and rail industries.

This report, available from the NetComposites website, relates to the Aerospace industry and focuses on the future research requirements of the aerospace sector in order to facilitate an increased use of composite materials.

The report states that composites are, besides aluminium, the most important materials for aerospace applications. Due to the opportunities they present for weight saving, their share has reached more than 15 % of the structural weight of civil aircraft, and more than 50% of the structural weight of helicopters and fighter aircraft over the last 40 years. In addition to their high mass specific stiffness and strength, the high potential of composites for additional functionality is another reason for their success. Defined anisotropic behaviour, the possibility to integrate sensors or actuators, high structural damping, and superior fatigue performance are typical advantages.

Nevertheless, there are still some drawbacks that are preventing composites from being used more extensively. Material costs can be prohibitively high, processing is time consuming and involves a lot of manual work, and the behaviour of the inhomogeneous and anisotropic materials is still not fully understood.

In order to discuss the most critical issues relating to the use of composites with experts from other transport sectors, ten workshops were organised within the framework of the COMPOSIT thematic network on “The Future Use of Composites in Transport”.

These ten workshops addressed the issues of composite repair, design and structural simulation, crashworthiness, manufacturing, lightweighting, joining, recycling, modelling, fire safety and new material concepts. The objective was to exchange knowledge in order to identify solutions or define common research directions. As an output from each workshop, priorities for future research activities to meet the needs of the transport sectors were identified.

This report presents the findings of COMPOSIT in terms of the aerospace industry. Key recommendations for future research priorities include:
Cost effective, automated manufacturing technologies, e.g. the development and application of textile preforming technologies in combination with non-autoclave impregnation and curing processes.
Improved design methodologies and analytical tools for simulating processing and performance (especially non-linear behaviour and long-term behaviour).
Improvement of material systems (fibres, matrix systems, binders) with respect to cost, processing and performance, e.g. through the application of nanotechnologies.
Advanced (adhesion) joining techniques for improving performance and simplifying processing.

Starting with projects such as the first fully-composite glider “Phönix”, a development at Stuttgart University in 1959, fibre reinforced polymers have gained an important role as structural materials in the aerospace industry. High specific stiffness and strength, superior fatigue performance, corrosion resistance and high energy absorption capabilities are the main properties that have led to a steady growth in the use of composites in all fields of aircraft and space application.

Market studies estimate that 2000 tons of finished composite parts, with a value of $760 million, were produced for the European aerospace industry in the year 2000.

The application of composites in place of metals requires different approaches to the design and service of structural components. Labour intensive manufacturing, expensive raw materials, damage tolerance aspects, and the need for new inspection and repair philosophies are all issues that need to be addressed. Furthermore, the differing requirements of civil and military aerospace applications need to be considered.

The challenge for all developments in aerospace is always to find a good compromise between performance and cost. Depending on the nature of the mission and the market, one or the other will dominate. A diagram in the report shows the goals for the next generation of Airbus planes, showing a 40% cost saving and a 30% weight saving which, compared to the state of the art cannot be reached by small steps. An integrated approach that takes all disciplines into account is necessary. With this in mind, recommendations for future research priorities are presented in the report.

The report concludes that whilst composite materials are well established in all aerospace fields, there are big opportunities to further intensify the use of composites for improving the performance and affordability of aerospace structures.

From the expected achievements of ongoing research and development programs, further improvements in mechanical performance, cost reduction and improved fundamental understanding can be anticipated. This will lead to composites becoming the number one candidate material for more and more components.

In civil aircraft, the next big steps could be the composite wing and the composite fuselage (Boeing 7E7). Current demonstration projects show promising results and the decision to employ a composite wing for the A400 military transport aircraft demonstrates the confidence in this application.

Technologically, many interesting topics are under continuous and successful development. Textile preforming, non-autoclave injection technologies, microwave-heating and health monitoring are only a few examples. In the longer term, further progress could also be realised through the use of nanotechnologies. In particular, carbon nanotubes look very promising as potential reinforcements to produce composites with unique performance.

A very important task is the development of integrated design tools that allow the simulation of the manufacturing process as well as the structural performance (short-term and long-term). This will reduce the development effort by limiting the number of experimental tests required. It will also further improve the utilisation of materials in the ongoing quest for optimised weight reduction.

Composite materials and structures have proven their potential for use in high performance aerospace applications over the last fifty years. High mass specific stiffness, strength and energy absorption, high functionality (e.g. through tailored anisotropy), and optimised structural concepts (e.g. due to high levels of design integration) are the main reasons for specifying composites.

The materials share for composites has reached 15 % in civil aircraft and more than 50% in military aircraft and helicopters.

Furthermore, there is considerable potential for further increases in these figures through applications such as the composite wing and composite fuselage, both of which are being investigated by Boeing and Airbus.

New developments such as textile preforming, liquid moulding technologies, advanced thermoplastic technologies, new material systems and optimised design methodologies will support this tendency.

Nevertheless, there is still a lot of research and development work to do. For many applications, costs are still too high compared to aluminium structures, even when life cycle costs are taken into account. Development times are still very long and the qualification of a new materials and processes is very expensive. Therefore, basic understanding of design, manufacturing processes, and in-service behaviour must be improved.

The unique feature of composites compared to metals is that the material and structure are produced in one step, and that there are many more factors influencing performance. On the one hand this is the reason for the success of composites. On the other, it is a challenge for future developments. Integrated approaches are required that take the material, process, structure and in-service conditions into account. The necessary tools must be developed to assist engineers in both the design and manufacturing phases.

Further information on COMPOSIT can be found at the CompositN website. The complete reports can be downloaded by clicking here.






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