Sharp Lines and Clear Skies: Writing Transparent Textures
Author: Samantha J. Stewart, Technical Research Scientist at NASA’s Marshall Space Flight Center
Reprinted from Journal of Aircraft, Vol. 36, No. 3 (July-September 1999)
Transparent materials are being used more and more in aircraft design. As the technology to produce them improves, so does the number of types available. The author reviews some of the newer types of transparent material which are becoming increasingly popular for the manufacture of aircraft parts such as windshields and canopy glazing.
F fundamentals
- The most important properties of a material in this application are its transparency, durability and resistance to impact.
- These materials must also be chemically stable and able to withstand the cleaning agents used for aircraft maintenance.
- The principal requirements for aircraft windshields and canopy glazing are similar. This means that any new material which can meet all of these criteria will certainly be adopted.
Cured Epoxy Resins
- Cured epoxy resins have been widely used for many years for making aircraft transparent components, although they are expensive. This cost is offset by their excellent durability and resistance to impact.
- The most common type of epoxy resin used for this purpose is a glass fibre reinforced, clear, two-part system.
- Although the use of epoxy resins offers many advantages, there are several disadvantages which limit their application. These include: high cost, sensitivity to moisture and chemicals, long cure times, yellowing after exposure to light.
Polymethyl Methacrylate (PMMA)
- PMMA is a thermoplastic material which has been used for many years in the aircraft industry. It is widely available, can be formed by injection moulding and is very transparent.
- The principal disadvantage of PMMA is its sensitivity to impact. Damage to the material must therefore be minimised during handling.
Tints and Coatings
- A number of tints and coatings are available for transparent materials, including some which give a slight blue colour in daylight and reduce reflections by up to 90%.
- However, the application of these tints and coatings can be difficult. They must therefore only be applied by highly skilled technicians.
Advances in Materials
- Recently a number of new transparent materials have been developed which offer improved properties compared to existing types, including: improved durability and impact resistance; reduced cost; increased transparency; and easy application.
- These new materials are also more environmentally friendly. They do not contain toxic chemicals like epoxy resins and can be recycled at the end of their life.
Future Developments
- The development of advanced composites which can be used as a replacement for metal in aircraft structures has recently accelerated. These materials offer improved strength, reduced weight, and increased corrosion resistance.
- Some of these new composites are already being tested for use on commercial aircraft.
Literature References
- 1. Stewart, S.J., et al: “Transparent Materials for Aircraft”, Journal of Aircraft, Vol. 36, No. 3 (1999)
- 2. Mummery, J.G., et al: “Transparent Epoxy Resins for Aircraft Windshields”, SAMPE Quarterly, Vol. 27, No. 2 (1991)