To Peel or Not to Peel?

Once a strain gage sensor is bonded to the test object, its tempting to test the quality of the bond by trying to peel the gage off the surface. Such a test is misleading, however, as strain gage sensor adhesives are formulated for optimum shear strength (for strain transmission) and not for high peel strength. This is a good thing, as adhesives with high peel strength — like those used on price tags or license plate stickers — are notoriously low in shear strength. So once the strain gage sensor is bonded, leave it alone. A far better way to check bond quality is to apply a test load and check for a good zero return.