REVIEW OF AEROSPACE APPLICATIONS

Application of advanced composites to aerospace can be divided into four categories: (1) aircraft, (2) rotorcraft, (3) spacecraft/missiles, and (4) engines/nacelle. Within each category a further division is possible. For example, aircraft can be divided into combat aircraft, large transport, and small aircraft, and further divided into military and commercial applications. The design and manufacturing technology is different for each of the above categories; the difference is largely dependent upon the requirements set forth by each category. A brief description of the requirements and constraints of each category is delineated below to help explain the impact on the design and manufacturing technology:

Aircraft

Combat.

This application requires high performance (weight, strength, stiffness are critical) and tolerance of severe environments. It involves moderate production rates and moderate durability. Many complex structures are required, resulting in high cost ($600 - $800 per pound of finished structure).

An automatic tape layup (ATL) machine is currently used for manufacturing large, somewhat flat structures, such as skins. An automatic cutting machine (ACM) is used to cut plies and fabrics for hand layup. Most of the complex and small parts are made by labor intensive hand layup.

Large Military Transport and Bomber. This application involves moderate to high performance in moderate to severe environments. Moderate production rates are typical and moderate to long durability is required. A mixture of large and small structures with both simple and complex shapes is fabricated for this application. The result is relatively high cost ($400 - $700 per pound of finished structure).

ATL is currently used for manufacturing large structures. ACM is used to cut plies and fabrics for hand layup. Most of the complex and small parts are made by labor- intensive hand layup.

Commercial Transport. This application involves moderate performance in moderate environments. Higher production rates are typical. Long-term durability is a requirement. The cost of certification is high. It entails the fabrication of a mixture of large and small structures with simple and moderately complex shapes. There is a high demand for low cost ($250 - $400 per pound of finished structure). Safety is a paramount consideration. Conservative approaches are typical due to the financial risks involved.

ATL is currently used for large structures in this application. ACM is used to cut plies and fabrics. Some filament winding is used, as is braiding for ducts and pultrusion for simple and long structures. The industry is still relying heavily on labor-intensive hand layup.

Small Transport and General Aviation. This is a relatively low performance application, in a less severe environment. Moderate to low production rates are typical. Short to medium durability is required. Certification cost is lower relative to the large transport category. Except for the wings and fuselage, small, less complex structures are involved for all-composite aircraft. Low cost is a must ($50 - $200 per pound of finished structure).

Mostly hand layup is used in current manufacturing practice. ATL and ACM are used for some applications. Filament winding is used for some structures. No fancy tooling or manufacturing techniques are employed.

Rotorcraft

Military.

This is a high performance application. Weight, strength, stiffness, and durability are critical. Operating environments are severe. Production rates are low to moderate. Battle damage tolerance is important. There is a high usage of composites (e.g., in rotor blades, tail blades, fuselages, and booms). Cost is relatively high ($500 - $700 per pound).

Hand layup is used for rotor and tail blade manufacturing. ATL and ACM are used for fuselage and boom. There are some filament winding applications.

Commercial and General Aviation. These aircraft require low to moderate performance, and usually operate in moderate environments. Production rates are low to moderate. In this industry, there is a high usage of composites for rotor blades, tail blades, bodies, and booms. Moderate cost ($200 - $350 per pound) is typical.

Hand layup is currently used for rotor and tail blade manufacturing. ATL and ACM are used for some body and boom structures. There are some filament winding applications.

Spacecraft and Missiles

This is a high to ultra-high performance area. Weight, strength and stiffness are extremely critical. There are numerous special and unique requirements. These vehicles operate in severe to extremely severe environments. Very low production rates are typical for some spacecraft (e.g., satellites) but high for some others (e.g., small missiles). There is essentially no durability requirement -- it is a "one shot" deal. Extremely high costs ($1,000 to over $10,000 per pound) are typical.

Current manufacturing techniques require the use of high precision hand layup with extremely complex tooling. Precision filament winding is used for circular shapes. Because of low production rates, labor-intensive hand layup is the main manufacturing technique.

Engine/Nacelle

There are uniquely high performance requirements for this application. These parts operate in severe environments. There is a high demand for durability. For fan blades, there is an acoustic environment issue, and net shape and complex contour are requirements. Relatively high production rates are a feature. Engine blades are expensive, whereas nacelles are produced at moderate cost ($770/lb finished in an automated process for blades, and $350 - $450 per pound for nacelles).

Precision hand layup is required currently for blade manufacturing. Tow placement is also used for this application. A combination of filament winding and hand layup is used for nacelles. Honeycomb construction is used for acoustic sound absorption in nacelles. Precision co-curing techniques are used for cascades.


Published: April 1994; WTEC Hyper-Librarian