This test method covers the determination of the peel resistance of adhesive bonds between: (a) a relatively flexible adherend and a rigid adherend; and (b) the relatively flexible facing of a sandwich structure and its core. It is described in test standard ASTM D1781.
In the case of an adhesive-bonded sandwich assembly, the face skin is peeled from around a circular flanged drum. A suitable top clamp secures the specimen and a drum clamp holds the adherend against the face of the drum. The drum is counterbalanced and as load is applied, it rotates as the outer surface is peeled over a distance of at least 150mm.
This test method is particularly sensitive to adherend surface-preparation and is of value where the adhesive is used in conjunction with a primer. When a relatively brittle adhesive is used, the peel resistance can often give an indication of the degree of cure .. i.e. higher values than normally realized may indicate an incomplete cure. The average peeling load is determined by calculation of values from the peel curve between 1"-5" (approx. 25 - 125mm).