Corrosivity Sensor Suite for Measuring Damage Accumulation from Corrosion in Aircraft Applications

Abstract

Structural integrity calculations are used to determine the lifetime of Defense aircraft structures, by predicting fatigue damage given a starting crack size. Presently, the effect of damage accumulation from corrosion is unaccounted for in these calculations. Corrosion is known to accelerate both crack nucleation and propagation, and without this knowledge of corrosion damage, structural integrity calculations could underestimate the potential lifetime of aircraft. Although a number of advancements have been made to establish diagnostic and prognostic systems for monitoring the corrosion of alloys used in aircraft, presently there are no viable continuous monitoring techniques that can provide direct, high resolution measurements of corrosion over large areas. Direct localized measurements of corrosion and environmental parameters, however, would improve fatigue management of aircraft by more accurately predicting the damage state and enabling more efficient condition based interval maintenance, replacing costly schedule based maintenance and inspection practices. A wireless corrosion monitoring system that can be retrofit into existing aircraft structures has been developed that combines localized measurements of corrosion and environmental parameters that contribute to corrosion with knowledge of aircraft usage to estimate current and future damage to aircraft. Numerous studies have linked environmental parameters, such as relative humidity and chloride concentration, to the corrosion of aircraft alloys. Sensors that measure these environmental parameters, including surface and air temperature, relative humidity, solution resistance, and polarization resistance have been integrated within a compact, robust package. The present development effort focused on establishing this sensing platform to measure environmental parameters, corrosion rates, and cumulative corrosion, and the application of these measurements to classify corrosivity and the structural health of aircraft are presented.