Structural Monitoring Via Embedded Magnetic Wires

Period of Performance: 04/24/2000 - 10/23/2000


Phase 1 SBIR

Recipient Firm

515 Schoolhouse Road
Kennett Square, PA 19348
Principal Investigator


Stress monitoring in composite materials is difficult but useful for testing to compare measurements with modeling and to monitor flexing and vibration under load. There are only a limited number of methods to measure strain that are suitable to be embedded in a composite material and all either expensive or complex. This proposal is for a new and novel strain sensor. It uses a small diameter wire coated with a magnetic film. The magnetic film dominates the impedance of the wire and is strain sensitive. The wire is very cheap to manufacture and the readout electronics simple so that overall system cost is low with a potential cost advantage over fiber optic sensors of a factor of 100. This proposal introduces a new technology with potentially wide applications. The ability to plate controlled magnetic films on small diameter wires opens multiple applications. The wire can be used to obtain curing information of a composite in addition to information on external strain. Since the system can be used in a modified array structure, the strain at different points can be measured versus time, giving information on the vibration of the structure, including modal analysis. This proposal addresses one specific application of a new technology, a wire sensor for embedding in composites to monitor internal strain, both initially and as the composite ages. Such sensors can be used to monitor the health of advanced composites used for airframes and space applications, as well as more conventional structures such as buildings, bridges, etc. Additional applications, including shielding and power filtering, are possible with a slightly different configuration of the wire.