AGING IN WIRE INSULATION UNDER MULTIFACTOR STRESS

A fundamentally based chemical-thermo dynamic multifactor stress aging functional relation requiring experimentally based constants is developed, based upon various theoretical models. The specific example presented is that for 120 V aromatic polyimide insulated wire. The stresses of water, temperature, and mechanical strain are included and electrical stress is considered. The results of over 2000 specimens are fitted to the theoretical trends. For a single independent variable function, the resulting relation reduces to the classical Arrhenius curve. The three independent variable relations presented here is applied to data from laboratory aging experiments that simulate insulation deterioration occurring in actual aircraft service experience. The results used in age categorization of US Navy aircraft are generated from wire specimens taken from active aircraft. The paradigm does not use ab initio based constants because of uncertainties in the theoretical development, two forms of which are presented; It is the aim of this presentation to provide a plausible, intuitively meaningful syllogism having elements transferable to other insulation materials/devices/systems, That transfer will require proper recognition of specific chemical mechanisms in the life calculation routine, constrained by practical secondary effects and the need of nonstandard statistics.