Pin Bearing Strength Test Fixture (ASTM D953)

Model No. WTF-PB (Stainless Steel)

IMG_3151

Fig. 1: Assembled D953 Pin Bearing Strength Test Fixture

ASTM D953 is a relatively old bearing strength standard (originally published in 1948), intended for testing rigid plastics, as the title of the standard implies (see Reference 1). This standard actually contains both tensile-mode and compressive-mode loading fixtures, although the latter fixture is seldom used. The standard tensile loading fixture is shown in Fig. 1 above.

The standard specimen is 4.75 in. long, 0.938 in. wide, and of a thickness equal to the diameter of the fastener hole used, viz., either 1/8 in. or 1/4 in..  Since the fastener hole sizes are different, two different fixtures must be used.  A ¼ in. diameter fastener is more commonly used.

Although originally developed for unreinforced plastics, this test fixture is sometimes used to test composites and other materials also, typically using the ¼ in. diameter fastener configuration.  And the condition specified in ASTM D953 that the specimen thickness is to be equal to the fastener diameter is often not maintained when testing these other materials. That is, non-conforming tests are often conducted, as for example are reported in Reference 2.

Alternate standards for bearing strength testing are also available, with alternate fixture configurations. See, for example, Sections H-2 and H-3 of this catalog (corresponding to References 3 and 4).  These fixtures may be more suitable for a particular application.

Source of Additional Information:

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

2) M. Akay, “Bearing Strength of As-Cured and Hygrothermally Conditioned Carbon Fibre/Epoxy Composites Under Static and Dynamic Loading,” Composites, Vol. 23, No. 2, March 1992, pp. 101-108.

3) 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).

4) 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).