Materials

Thermoplastic polymers such as acrylic materials are used in numerous aircraft and rotorcraft applications because it readily accommodates the manufacture of clear lightweight complex-shaped transparencies. As-cast acrylic is typically used for helicopters and non-pressurized aircraft transparencies.

Stretched acrylic is obtained by stretching as-cast acrylic sheets, a process which reorientates the long polymer chains. Stretching drastically increases the material properties. Stretched acrylic offers an improved craze resistance, increased stress tolerance, crack propagation and solvent resistance than as-cast acrylic. It is therefore suitable for birdproof windshields, canopies, outer cabin window panes and other transparencies for pressurized aircraft.

Polycarbonate materials possess exceptional strength and provide high impact resistance which make it the ideal material for the design of windshields subjected to high velocity birdstrikes. It is lightweight and provides excellent high-temperature tolerance. Susceptible to stress-solvent crazing, it is recommmended that polycarbonate items be used only with an applied protective coating.

Protective Coatings for acrylic and polycarbonate are used to prevent deterioration from weather extremes including ultraviolet rays, solvents and chemicals as well environmental conditions such as abrasion caused by sand and dirt. Coatings can be applied by means of flow, dip or spray and are generally thermally cured.

Several coating systems are available and the choice is dependent upon the desired performance requirements.