Health monitoring for aircraft structures

Over the last two years, Southwest Research Institute has been examining the potential for using nickel foil magnetostrictive sensor technology for monitoring bond quality and discontinuity growth under patches as well as discontinuities around and under fasteners. The nickel foil magnetostrictive sensor is low profile and low cost and is adhesively bonded to the surface of the component to be tested and monitored. Preliminary studies have shown that discontinuity changes under fasteners as small as 1.3 mm (0.05 in.) for notches and simulated corrosion can be observed using the magnetostrictive monitoring technology. Small changes in bond quality are also detectable. Growth of discontinuities under the bonded patch on the order of several millimeters can be detected. Issues associated with using magnetostrictive sensor technology, such as bonding of the nickel foil to the component and the effect of environment, have also been investigated. The tests conducted and the results obtained are reported in this paper.