ASTM D1781
Climbing Drum Peel Test Fixture
Standard Test Method for Climbing Drum Peel for Adhesives - PDF
ASTM D1781 Peel Fixture – Universal Grip Data Sheet (PDF)
What Is ASTM D1781?
ASTM D1781 is the climbing drum peel test for adhesives. A flexible facing is peeled from a rigid sandwich core or laminate by winding it onto a drum that climbs up the specimen as the testing machine pulls straps wrapped around larger flanges on each side. The result is a peel torque per unit width. It is the standard check of facing-to-core bond quality in honeycomb and foam-core sandwich panels for aircraft, transit and marine structures, and of the bond in metal-faced laminates.
Specimens
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Sandwich construction: 76 mm (3 in) wide between saw cuts and at least 305 mm (12 in) long, with about 25 mm (1 in) of one facing overhanging at each end for clamping. The reference facing is 0.51 mm (0.020 in) 2024-T3 clad aluminum on a 12.7 mm (0.5 in) core.
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Laminates (metal-to-metal or similar): 25 mm (1 in) wide and at least 254 mm (10 in) long.
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Condition at 23 ± 2 °C and 50 ± 10% RH, and test at least six specimens.
Equipment
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Universal testing machine with a constant crosshead speed and a load cell sized for the peel load (usually well under 5 kN).
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Climbing drum peel fixture: a drum with larger flanges on each end; straps wound around the flanges hang the drum from the moving crosshead, and the flexible facing is clamped to the drum.
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Grips or a clamp that holds the rigid end of the specimen below the drum, square and in line with the load.
Test Procedure
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Clamp the overhanging facing to the drum and the other end of the specimen to the lower grip, with the specimen vertical.
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Pull at 25.4 ± 2.54 mm/min (1.00 ± 0.10 in/min); the drum rolls up the specimen and peels the facing from the core.
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Peel at least 150 mm (6 in), recording load against crosshead travel, and ignore the first 25 mm (1 in) of peel.
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Run the drum without a specimen at the same speed to measure the resisting load F0 (the force to lift and wind the drum).
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Record the average, maximum and minimum peel loads and the failure mode (adhesive, cohesive or core).
Peel Torque Calculation
T = (Fp − F0) × (rf − rd) ÷ W
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T = average peel torque per unit width (in·lbf/in or N·mm/mm)
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Fp = average peel load; F0 = load to overcome the drum resistance
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rf = flange radius (to the center of the strap); rd = drum radius plus half the facing thickness
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W = specimen width
Example: on a drum with 0.5 in between the flange and drum radii, a 3 in wide sandwich specimen averages 60 lbf against a 15 lbf empty-drum load. T = (60 − 15) × 0.5 ÷ 3 = 7.5 in·lbf/in (33 N·mm/mm).
Related Peel Standards
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ASTM D3167: floating roller peel resistance of adhesives
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ISO 11339 / ISO 4578: T-peel and floating roller peel equivalents
ASTM D1781 FAQ
What test speed does ASTM D1781 use?
25.4 ± 2.54 mm/min (1.00 ± 0.10 in/min) crosshead speed.
What size are ASTM D1781 specimens?
Sandwich panels: 76 mm (3 in) wide and at least 305 mm (12 in) long, with about 25 mm of one facing overhanging each end. Laminates: 25 mm (1 in) wide and at least 254 mm (10 in) long.
How is climbing drum peel torque calculated?
T = (Fp − F0) × (rf − rd) ÷ W: the average peel load minus the load needed to roll the empty drum, times the difference between the flange and drum radii, divided by the specimen width. Results are in in·lbf/in or N·mm/mm.
Why subtract the empty-drum load?
Part of the measured force only lifts and winds the drum and its straps. Running the drum without a specimen gives that resisting load (F0), which is subtracted so the result reflects only the bond.
For more on the fixture itself, read our climbing drum peel fixture guide.