FATIGUE STRAIN GAUGES

• US 3,779,071 A
• Filed: 09/13/1971
• Issued: 12/18/1973
• Est. Priority Date: 09/13/1971
• Status: Expired due to Term

• Current Assignee: Tracor Aerospace, Inc. (BAE Systems Plc)
• Original Assignee: Alvin D. Thomas Jr, Joseph Scott Thornton
• Inventors: Thomas, Alvin D. Jr., Thornton, Joseph Scott
• Primary Examiner(s): Myracle, Jerry W.
• Application Number:
  US05/180,007
• Time in Patent Office: 827 Days
• Field of Search: 73/88.5R 338/2,114
• US Class Current: 73/767
• CPC Class Codes: G01N 3/18 Performing tests at high or low temperatures

Abstract

Safety gauges for indicating the internal state of structural materials and methods for determining fatigue of such materials, are provided. In one embodiment, an integral gauge is provided for use in a composite matrix-reinforcing fiber material, the gauge being constructed of like matrix-reinforcing fiber material having therein at least one conducting filament. In another embodiment, a gauge of this type is constructed having a bundle of conducting fibers, and the gauge is bonded to the exterior of a structural part. Conducting fibers are separated from one another by matrix material, to the maximum practical extent.

Claims

1. A safety gauge suitable for measuring irreversible mechanical damage in a structural part during or after use thereof, said gauge being incorporated in said structural part as an integral part thereof and comprising:

a resin matrix material;

a bundle of conducting graphite filaments disposed in said matrix material, said filaments being generally separated from adjacent filaments by matrix material;

means to measure the resistivity across said filament bundle;

electrical leads attached to the ends of said filament bundle and to said measuring means, whereby the resistivity across said bundle is measured to determine the fatigue of said structural part during or after use thereof, fatigue being indicated by fracture of some or all of said filaments.

2. A safety gauge suitable for measuring irreversible mechanical damage in a structural part during or after use thereof, said gauge being bonded to said structural part by a suitable adhesive agent and comprising:

a resin matrix material;

a bundle of conducting graphite filaments disposed in said matrix material, said filaments being generally separated from adjacent filaments by matrix material;

means to measure the resistivity across said filament bundle;

electrical leads attached to the ends of said filament bundle and to said measuring means, whereby the resistivity across said bundle is measured to determine the fatigue of said structural part during or after use thereof, fatigue being indicated by fracture of some or all of said filaments.

3. A safety gauge in accordance with claim 2, wherein said matrix material is an epoxy resin.

4. A safety gauge in accordance with claim 2, wherein said gauge additionally includes reinforcing glass fibers disposed in said matrix material.

5. A safety gauge in accordance with claim 1, wherein said matrix material is an epoxy resin.

6. A safety gauge in accordance with claim 1, wherein said gauge additionally includes reinforcing glass fibers disposed in said matrix material.