Installing Strain Gages on Fiberglass

Fiberglass is used as a structural material, and it is found all around us in such things as automotive bodies, boat hulls, sports equipment, utility enclosures, etc.  Installing strain gages on fiberglass laminates is a fairly straightforward process as long as the correct steps are followed:

1. Select a strain gage with an active grid length of sufficient length to span 3-5 repetitions of the fiber.  Typically, a resistance of 350 or 1000 ohms is preferred since fiberglass is a poor heat sink and the higher resistance helps reduce self-heating, thus improving zero stability.
2. Degrease the surface with GC-6 Isopropyl Alcohol.
3. Lightly abrade the surface with 400-grit Silicon Carbide Paper, just enough to remove all surface gloss.  Do not abrade too far as it is important not to damage the glass fibers; this would reduce structural strength.
4. Mark the gage location.  Avoid surface contamination and damage.
5. Scrub with Micro-Measurements Conditioner A and then wipe dry.
6. Scrub with Micro-Measurements Neutralizer 5A and then wipe dry.
7. Bond the gage with Micro-Measurements M-Bond 200 or AE-10 adhesive
8. Install leadwires
9. Apply appropriate protective coating
10. Test