THERMAL REQUIREMENTS FOR FUNCTIONAL TEXTILES

We all know that modern aircraft, through the ability to maintain continuous speeds in excess of Mach 1, have placed excessive burdens on those responsible for development of materials capable of withstanding high temperatures. These temperatures, of course, are created by aerodynamic and engine heating. Also, textiles have a place in these aircraft in many unusual applications. To visualize the part textiles play in these new and high-speed combat aircraft, three factors must be realized: (1) crews and equipment must be protected from aerodynamic heat and blasts of high intensity radiant heat; (2) weapons must be delivered with a controlled accuracy; and (3) deceleration of the aircraft, if required in an emergency, and safe recovery of the crew must be ensured. With respect to the first factor, fibrous battings and coated fabrics are used to impart the necessary protection. In the latter two areas, textiles are used in the form of parachutes to obtain the desired results. Before considering the details of materials used and needed, a look a t the areas of concern is in order. FIGURES 1to 6 will give the reader an idea of them, including thermal blanket, sun shade, the weapons-delivery chute, recovery of aircraft, re-entry, and the latest personnel parachute. These are the general areas that I propose to discuss, including what is used in the way of textile materials, deficiencies that exist, approaches being studied and, ultimately, what is required for an optimum material. To simplify this discussion, I shall classify materials used in two categories: parachute materials and functional materials. Because the latter require minor consideration, I shall discuss them first. One aeronautical area where thermal radiation constitutes a major problem is insulation for personnel and equipment in aircraft. Normally these blankets consist of: (1) coated fabric; (2) Fiberglas batting; (3) cotton or nylon scrim (optional) ; and (4) vapor barrier. To prevent water penetration, sewn quilting has been eliminated in favor of new high-temperature adhesives. In this application light weight, excellent tear strength, and flame resistance are required for the coated fabrics. A coated fabric that will take the vertical flame test described in CCC-T-l9lb, with a maximum of 2 seconds' flame time and 3 seconds' glow time, is considered satisfactory. Of course, it must be remembered that the fabric cannot promote corrosion (that is, coating). Let me add another and somewhat new requirement. I know that Mylar and Polyethylene, which are vapor barriers, fail a t low temperature. Most of the coatings cannot withstand much more than 450" F. We are now interested in temperatures of 700" F. built up by aerodynamic friction on the aircraft skin. Even higher temperatures can exist; for actual data we must wait until some of the newer aircraft are flight-tested. It is obvious that it will be necessary to replace some of the present vapor-barrier materials. Coatings will be called on to withstand temperatures of 700" F. for periods of 10 to 30 sec. The basic fabric must be just as resistant to heat as the coating. On this application the weight will be very important. Weights of less than3 oz./sq. yd. for thecoated