Composites in aerospace

The choice of materials, whatever the industry - aerospace, automotive, rail, sports and leisure, construction, civil engineering... - is always a complex problem where the cost/performance trade-off reigns supreme.

In Europe today, the aerospace market accounts for some 120,000 tonnes of materials used annually in the manufacture of structures (aircraft, helicopters, satellites, missiles), which is relatively modest when compared with the automotive industry alone, which accounts for a tonnage of materials used some 100 times higher.

In commercial aircraft, the first mass-produced industrial aircraft used mainly aluminum alloys, steel and titanium. Today, the most recent commercial aircraft still use 54% aluminum alloy by mass, but 20% composite materials have been introduced in the structure, 13% steel, 6% titanium and 7% various materials.

The main advantage of composite materials is that they offer weight savings of between 25% and 30% on the final structural part, compared with an aluminum alloy solution, while retaining excellent mechanical properties. The notion of comparative costs between a composite solution and a metal solution, however, is a complex and delicate one to master, depending on whether we are talking about the purchase cost of basic materials, where the price of prepregs is more than ten times higher than the price of aluminum alloy, or the cost price of the elementary part or complete subassembly, with or without the integration of maintenance costs over the life of the product.

The main materials used for fibers are carbon, glass and aramid. Matrices are mainly epoxy thermosets for structures, and phenolic thermosets for interiors. Thermoplastic matrices are beginning to be introduced for primary structures.

In this article, we present the advantages and disadvantages of composite materials for the production of structural parts for aircraft, helicopters, satellites and missiles, from both the manufacturer's and the end-user's point of view. In the final section, we will look at trends in the use of composites in aerospace structures.