IITRI COMPRESSION TEST FIXTURE  (ASTM D 3410)

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

Exploded View of IITRI Fixture

The IITRI Compression Test Fixture, introduced by the Illinois Institute of Technology Research Institute (IITRI) in 1977 (Reference 1), became part of ASTM Standard D 3410 in 1987 (Reference 2). The IITRI test fixture configuration incorporates flat wedge grips, as shown, which make full surface contact with the mating blocks, independent of the tabbed specimen thickness.

Alignment rods in linear bearings are used, rather than an external alignment sleeve as in the Celanese fixture. This minimizes frictional binding between the fixture halves.

The Wyoming version includes an upper bracket attached via an adapter to the crosshead of the testing machine. This permits easy slip-in installation and removal of the heavy upper block. The lower block normally rests freely on the base of the testing machine, although threaded attachment holes are also provided.

The Wyoming version of the IITRI Compression Test Fixture is designed to accommodate tabbed specimens up to 5.5" long, and of any width up to 1.5", as specified by the ASTM standard. For example, the fixture can accommodate a Celanese specimen, which is also 5.5" long, but only 0.25" wide.

The Wyoming IITRI fixture is supplied with three sets of wedge-shaped spacers, which can be interchangeably inserted in the cavities of the upper and lower blocks, to accommodate tabbed specimens of a wide range of thicknesses. The approximate thickness ranges are (assuming the wedges are flush with the blocks when at the lower end of each range, and protruding a maximum of 0.50" at the upper end of each range): Low Range: 0.17"-0.35"; Medium Range: 0.29"-0.47"; High Range: 0.42"-0.60". That is, each set of spacers provides a tabbed specimen thickness range of about 0.18", with an approximately 0.05" overlap between ranges.

The standard gage length (distance between specimen tabs) per ASTM Standard D 3410 is 0.50". The fixture can be used to test nonstandard gage length specimens also, from zero to approximately 2". (With longer alignment rods, specimens of longer gage lengths can be used.)

Partially Disassembled Fixture, with Extra Set of Wedge Grips Shown in Installation Jig

The Wyoming IITRI fixture includes an installation jig with centering bars for four different specimen widths.

All accessory parts for each fixture are supplied in a foam-lined, wooden storage case, fitted with brass hinges, latch, and side handles. This provides an attractive and protective case for the various accessories when not in use.

Sources of Additional Information:

1)     1)  Hofer, K.E., Jr. and Rao, P.N., "A New Static Compression Fixture for Advanced Composite Materials," Journal of Testing and Evaluation, Vol. 5, No. 4, July 1977, pp. 278-283.

2)     2)  ASTM Standard D 3410-03 (2003), "Compressive Properties of Polymer Matrix Composite Materials with Unsupported Gage Section by Shear Loading," American Society for Testing and Materials, West Conshohocken, PA (first published in 1975).

3)     D.F. Adams, "Current Status of Compression Testing of Composite Materials," Proceedings of the 40th International SAMPE Symposium, Anaheim, California, May 1995, pp. 1831-1843.

4)     D.F. Adams and E.M. Odom, "Influence of Test Fixture Configuration on the Measured Compressive Strength of a Composite Material," Journal of Composites Technology and Research, Vol. 13, No. 1, Spring 1991, pp. 36-40.

5)   5)  J.S. Berg and D.F. Adams, "An Evaluation of Composite Material Compression Test Methods," Journal of Composites Technology and Research, Vol. 11, No. 2, Summer 1989, pp. 41-46.

6)   6)  J.S. Welsh and D.F. Adams, “Current Status of Compression Test Methods for Composite Materials, “ SAMPE Journal, Vol. 33, No. 1, January 1997, pp. 35-43.

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