A functional evaluation program was established which will provide a comparison of thermal service life of wire and cable insulation by combining the effects of heat aging with the most predominant service stresses. The stresses are necessarily of greater severity than normal service and thus provide relative life data rather than absolute values of service life. Experimental data of life versus aging temperature when statistically treated and the log of life versus the reciprocal of the absolute temperature plotted on semi-log paper approximates a straight line which can be represented by the Chemical Rate Equation. Temperature cycling studies conducted on a representative magnet wire insulation system indicate that reasonable estimates of service life under varying temperature conditions can be obtained by applying the relative aging factor principle. From the life versus temperature curve a relative aging factor can be derived which can be applied to convert aging time at any given temperature to a relative amount of normal life consumed at a reference temperature. When the high temperature exposures occur in known service cycles, it is possible to calculate the number of cycles of safe operation which can be expected of the cable. (Author).

Life versus temperature curves of wire and cable insulations are needed to provide aircraft design engineers with information to design electrical circuits utilizing the minimum wire sizes required to maintain maximum reliability and yet reduce weight and bulk to a minimum. To establish the feasibility of obtaining such curves a procedure, employing functional evaluation and principles of statistical analysis, was developed and applied to produce curves of five wires representing the variations in insulation layer constructions specified in MIL-W-5086A. Cycling temperature studies were conducted on three of these wires, verifying the application of a relative aging factor formula which can be used to convert cyclic aging to the equivalent aging of a single temperature exposure. (Author).

"The purpose of this initial research program was to evaluate the aging characteristics of three types of aircraft electrical wire : polyimide, poly trafluoroethylene/polyimide composite, and polyvinyl chloride/nylon. In addition, predictive models for the aging of these wire types were developed. These wire types were chosen because of their widespread use in commercial aircraft and the amount of reported incidents concerning them. The factors that cause the wire insulation to degrade were examined and techniques to determine when a wire will no longer be capable of transfer of electrical current were evaluated. The results in this study provided a platform to evaluate existing and new test methods that could be used to monitor the aging of wire in aircraft."--Report documentation page.

"The purpose of this initial research program was to evaluate the aging characteristics of three types of aircraft electrical wire : polyimide, poly trafluoroethylene/polyimide composite, and polyvinyl chloride/nylon. In addition, predictive models for the aging of these wire types were developed. These wire types were chosen because of their widespread use in commercial aircraft and the amount of reported incidents concerning them. The factors that cause the wire insulation to degrade were examined and techniques to determine when a wire will no longer be capable of transfer of electrical current were evaluated. The results in this study provided a platform to evaluate existing and new test methods that could be used to monitor the aging of wire in aircraft."--Report documentation page.