Investigation of Strain Sensing Capabilities of Amorphous Magnetostrictive Wires Embedded in Epoxy Resin

Abstract

The development of fibers and adhesive systems with high durability has recently led to the creation of a new repair method of metallic structures, by the use of reinforcing patches made of composite materials. This technique is generally reported as "Composite patch repair" and provides very important advantages compared to the conventional methods of repairs. On the other hand, the technology of induction heating constitutes an innovative approach to achieve the supply of energy for the curing of resins or for the manufacturing of composite materials. In the case of resins, a ferromagnetic material must be imported into the resin, to produce the required heat. This may be achieved by importing a metallic grid in the resin. Moreover, this metallic grid, which remains inside the resin after the curing, may serve as sensor by analyzing its electrostatic properties, thus providing useful information about the structural integrity of the area (e.g. potential increase of the crack below a bonded composite repair). In this paper we present results concerning the strain sensing capabilities of amorphous magnetostrictive wires embedded in epoxy resin. The inverse magnetostrictive effect leads to a change of permeability of wires so that applied stress can change the impedance of the amorphous wires due to the skin effect with alternating current excitation. Two different types of sensing were used, contact sensing (attachment of the wire “gauge” to a sensing devise) and induction sensing (eddy current sensing probe).