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Plastics for Aerospace Vehicles - Part II - Transparent Glazing Materials

This handbook has been prepared for the Air Force to provide information for the selection 
of transparent glazing materials and the factors to be considered in their installation and 
use in military aircraft. 
In the last decade, aircraft glazing configurations have become incrcasingly complex, to 
the extent of not only performing as structural members but also as protective coverings 
in a wide variety of situations. Structural loading in the flight profiles Of high-performance 
aircraft involves not only differentials between cockpit pressurization and outer ram air 
loading, but also transient thermal conditions that tax the lower extremities of material 
strength spectrums. 
Adding the protective features usually increases the transparency thickness and weight 
beyond that required for structural integrity. If a special coating is required, an additional 
transparent coating or sheet is often necessary to protect the active coating from damage. 
In situations where differences of thermal expansion coefficients are critical between two 
rigid materials, a separating elastic interlayer is added as a further complexity. With one 
exception, any of the additional protective features will act negatively toward light trans— 
mission and optical integrity. 
The design engineer has to carefully evaluate the structural and protective requirements 
of the aircraft transparency, keeping in mind that the final design must meet certain optical 
requirements which can be very critical in areas used for landing or gun—sighting operations 
and less critical in general viewing areas.

The data on the mechanical, thermal, optical, and other properties of transparent plastics 
and glass have been selected from a number of specifications and reports. Sufficient test 
data were not available on all materials for establishing design allowables. Therefore, some 
material property data are only representative values and should be considered as such. 
Because most configurations are complex, the designer should prepare test specimens of 
the final design configuration and conduct confirmation tests of all critical design factors. 
The format essentially starts with materials and sources available for transparent enclosures 
and includes both glazing and supplementary materials for the design and manufacture of 
composite constructions. considerations follow which concern allowable strength 
values and a discussion of some of the more critical properties that influence desi*l. The 
majority of the technical data is presented in Chapter 4, which treats each type of monolithic 
transparent sheet as a separate entity and is grouped in two parts, Mth military specified 
materials divided from those which are being considered for aircraft use.