NASA 90-Degree Peel Test Fixture

Model No. WTF-ND (Stainless Steel)

IMG_3469

Fig. 1: NASA 90-Degree Peel Test Fixture without specimen installed.

The NASA 90-Degree Peel Test Fixture (Reference 1) is designed to maintain a constant 90 degree peel angle as a face sheet is peeled from the remainder of a honeycomb sandwich panel. Other structures consisting of a flexible face sheet and a more rigid substrate can also be tested using this fixture, including a flexible adherend bonded to a rigid adherend.

It is claimed in Reference 1 that a 90-degree peel test produces more consistent results than the Climbing Drum Peel Test Method when a thin face sheet (less than 0.015 in. thick) is to be peeled. Face sheet thicknesses less than 0.010 in. are recommended. The NASA test fixture pulls the face sheet around a roller only 1 in. in diameter, as opposed to the 4 in. diameter drum of the Climbing Drum Peel test fixture.

The fixture is shown in Fig. 2, with a dummy specimen inserted for illustration purposes. Note that the top left roller, provided to restrain the rigid lower portion of the specimen, is adjustable. This permits the testing of thick as well as thin flexible adherends, by maintaining the rigid lower adherend in a horizontal plane for any thickness of flexible adherend being tested. The two lower rollers are also adjustable, to accommodate specimens of different total thickness. These rollers constrain the specimen to remain horizontal. The free end of the flexible adherend is gripped in a standard tensile grip. The fixture itself contains a threaded hole in the bottom, for attachment to the base of the testing machine.

nasa 90 degree peel test fixture_0

Fig. 2: NASA 90-Degree Peel Test Fixture with  specimen installed for testing.

The fixture shown will accommodate a specimen up to 2 in. wide and up to 1 in. thick, with a flexible face sheet up to 0.20 in. thick. The specimen should be at least 10 in. long, with at least 2 in. of unbonded face sheet at one end. The NASA document (Reference 1) recommends a 2 in. wide specimen.

The fixture can be modified as required to accommodate specimens of other sizes.

Source of Additional Information:
1) NASA Tech Brief 65-10173, "Peel Resistance of Adhesive Bonds Accurately Measured," NASA Goddard Space Flight Center, Greenbelt, Maryland, June 1965.