How can I test the Strength of Glue?
There are a number of ways of specifying the ‘goodness’ of an adhesive. For a start, there’s the tensile strength, the shear strength, and the modulus. Tensile strength: Get two bits of wood (square cross-section), some string, and a plastic bag. Tie the string around the ends of one length of wood and hang it so that the wood is lying horizontally. /\ string / \ —– wood Glue the second piece of wood to the underside of the first, with the two bits of wood in a cross-shape when seen from above. Hang the plastic bag over the ends of the 2nd bit of wood. Load the plastic bag till the glue fails, weigh (or measure in some other way) the contents of the plastic bag, answer in Newtons ideally. Measure the area where the bits of wood overlap. Ideally, convert to metres squared. The tensile failure stress (Pa) = force (N) / area (m^2) Shear strength. I leave this as an exercise for the student. Basically, you want the force this time to be in the plane of the glue, not at right-angles to i
