Originally Posted by
Bob H
Can you provide the source for the test strip tests so I can see what they want?
Generally, adhesives are tested with adherencds of the same materials that are being bonded, then those "lap shears" are pulled in a tensile testing machine to measure the force required to break the bond. That force divided by the bond area gives the shear strength of the coupon.
Adhesive failure modes are "adhesive" and "cohesive". Adhesive failures are between the base material and the glue; cohesive failures are within the glue. Ideally, you want failures to be cohesive because that indicates that the glue has reached all of it's capability. But most failures are a combination of the two modes and are reported as percentages of each mode.
When an epoxy adhesive vendor reoprts his adhesive's strength, it's usually done on aluminum adherends 1" wide and 6" long and .025" thick. This gives high numbers, like 3500 psi. A wood joint would probably never come close to such values and the failure would be in the wood peeling apart. I would consider that a successful test of the adhesive.