SACMA Bearing Strength Test Fixture (SACMA SRM 9-89)

Model No. WTF-LB-SACMA (Stainless Steel)

IMG_3125

Fig. 1: Assembled SACMA SRM 9-89 Bearing Strength Test Fixture

The SACMA Bearing Strength Test Fixture (Reference 1) is shown in Fig. 1.This fixture also satisfies the requirements of ASTM D5961 (Reference 2), and has also been adopted by Composite Materials Characterization, Inc. (Reference 3) as their standard fixture.  ASTM D5961 actually contains a simpler fixture, which although functional, is not as convenient to use. The ASTM fixture is described in Section H-3 of this catalog.

The SACMA fixture is shown disassembled in Fig. 2. This fixture incorporates bushings in housings that can be screwed in and out to accommodate specimens of varying thickness.  Thus, no shimming between the specimen and the fixture is required. (Two extra pins, available as options as are extra bushings, are also shown in Fig. 2.)

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Fig. 2: Disassembled test fixture

The testing principle is the same for both the SACMA and ASTM configurations. A composite laminate (often quasi-isotropic) of thickness typically in the range of 0.10 in. to 0.25 in. is loaded in bearing by a close fitting ¼ in. diameter fastener or pin. The applied load and the associated deformation of the hole are monitored.

Occasionally, nonstandard specimen configurations are to be tested, requiring a special test fixture, such as shown in Fig. 3.

sacma bearing strength test fixture_2

Fig. 3: Special SACMA Bearing Test Fixture (left) incorporating a 1/2" diameter pin, compared to a standard size SACMA fixture (right).

ASTM D 953 (Reference 4) also exists. Although originally developed for testing unreinforced plastics, it has been used for testing other materials also, as discussed on its own page.  It utilizes a much simpler test fixture.

Source of Additional Information:
1) 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).

2) ASTM Standard D5961/D5961M-13 (2013, "Bearing Response of Polymer Matrix Composite Laminates," American Society for Testing and Materials, West Conshohocken, Pennsylvania (first issued in 1996)

3) CMC Screening Method P6-7, "Bolt Bearing Strength Test," Composite Materials Characterization, Inc., Richardson, Texas, Revised June 1999 (first issued in 1994).

4) ASTM Standard D953-10 (2010), "Bearing Strength of Plastics," American Society for Testing and Materials, West Conshohocken, Pennsylvania (first issued in 1948).