ASTM D5961 BEARING STRENGTH TEST FIXTURE  (ASTM D 5961)

Model No. CU-LB-D5961  (low carbon steel)
Model No. WTF-LB-D5961  (17-4PH stainless)

This test method is presented as Procedure A in ASTM D 5961 (Reference 1).  It is intended for testing composite laminates in double shear.  The standard test specimen is 5.5” long and 1.5” wide, with a specified thickness in the range of 0.125” to 0.208”.  A ¼” diameter fastener is used. 

The simple test fixture is shown in the photograph below.  The two halves of the fixture are separated by a spacer (not provided) of the same thickness as the specimen being tested.  Obviously, a piece of the same test material can be used as a spacer, if desired.  The test specimen is pinned in the other end of the fixture using the ¼” diameter hardened steel pin provided, or a lightly torqued (20-30 in-lb) fastener, if desired.

The Fixture is shown Assembled at the Left:
a Disassembled Fixture is shown at the Right

The end of the fixture with the spacer in place is gripped in a standard tensile wedge grip.  Each half of the fixture is 0.2” thick; thus this grip must have an opening range to accommodate 0.4” plus the spacer (specimen) thickness.  The free end of the specimen is held in a second tensile wedge grip.

A tensile loading is applied until a maximum loading has been reached, monitoring both applied force and hole deformation, as described in the ASTM standard.

An alternate version of the test fixture shown here, that also satisfies all of the requirements of ASTM D 5961, is the so-called SACMA test fixture (see Section H-2 of this catalog, and Reference 2).  As described in Section H-2, the SACMA fixture is much easier to use since the specimen holder is one piece, with adjustable bushings to accommodate variations in specimen thickness.

Sources of Additional Information:

1)     1)  ASTM Standard D5961/D5961M-96 (1996), "Bearing Response of Polymer Matrix Composite Laminates," American Society for Testing and Materials, West Conshohocken, Pennsylvania (first issued in 1996).

2)     2)  SACMA Recommended Method SRM 9-89, "Bearing Strength Properties of Oriented Fiber-Resin Composites," Suppliers of Advanced Composite Materials Association, Arlington, Virginia, 1989 (now discontinued).