Scope:

ASTM D1781 is a standard test method for determining the adhesive bond peel resistance on items with a flexible adherend and a rigid adherend surface. By removing the sandwich assembly’s face, this standard can also be used to examine the structure and core of a sandwich. The purpose is to determine how much torque is needed to peel the two materials. The ASTM D1781 test is most commonly used in A-B comparison testing, which compares the outcomes of two alternative process conditions in order to improve a process. For moderately brittle adhesives, peel resistance may also indicate the degree of cure.

Procedure:

The climbing drum peel fixture with the specimen is put in the test frame for the ASTM D1781  test process. The average peeling load between 1 inch and 6 inches of adherend separation is determined by applying a tensile force at a constant rate of crosshead separation. The amount of crosshead movement required is determined by the ascending drum peel fixture’s shape. A  standard formula is used to calculate the average peeling torque or average peeling load. 

Video 01: ASTM D1781 Climbing drum peel test on an aluminum composite panel

Specimen size:

As per the ASTM D1781 test method: 

➢ For evaluation of adhesives in laminated assemblies, the specimen is 25 mm wide between saw kerfs and at least 254 mm long. 

➢ For evaluation of adhesives in sandwich constructions, the specimen is 76 mm wide and at least 305 mm (12 in.) long. 

Data : 

According to the ASTM D1781 test, the average peel torque, T, is calculated as follows. T=[(R-r)(F-f)]/W]

where,  

T = average peel torque, mm.kg/mm of width

R = radius of the flange, including one half the thickness of the loading straps, in mm  

r = radius of the drum plus one half the thickness of the adherend being peeled, in mm  

F = average load required to bend and peel the adherend plus the load required to overcome the resisting torque, kg  

f = load required to overcome the resisting torque, in pound and  

w = width of the specimen, in mm

Conclusion:

ASTM D1781 is a standard test method for determining the adhesive bond peel resistance on items with a flexible adherend and a rigid adherend surface.