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LONG BEAM FLEXURE TEST FIXTURE (ASTM C 393) Model No. CU-LF (aluminum and low carbon steel)
This test method was first standardized as ASTM C 393 in 1957 for sandwich panel testing (Reference 1). However, it is also useful for flexural testing any other type of specimen, e.g., solid laminates per ASTM D 790 and ASTM D 6272 (References 2 and 3). The standard Long Beam Flexure Fixture can also be customized to accommodate specimens of other practical maximum lengths and widths. ASTM C 393 permits the use of either single (midspan) loading, or two-point loading (the set-up shown in the photographs). These are usually termed three-point and four-point flexure, respectively. The fixture can be used in either configuration, one loading head being removed and the remaining one centered on the loading beam to perform three-point loading. To keep the total weight of the fixture reasonable, the loading and support beams and the loading and support heads are fabricated of high strength aluminum rather than steel. The total weight of the fixture is approximately 40 lb. Optional alignment rods and bearings as shown in the following photograph add 15 lb.
ASTM C 393 also permits the use of cylindrical loading and support points. The Wyoming fixture incorporates pivoting flats, as shown in the above photographs. A close-up of a pivoting flat is shown in the following photograph. These pivoting flats can be easily removed, however, and the specimen loaded/ supported directly on the hardened 0.50" diameter pivots, if desired.
A wide array of other loading and support configuration accessories is also available, including wider and narrower loading flats, loading cylinders of various diameters, and specimen centering stops. In use, the fixture is attached at both top and bottom to the testing machine. For this purpose, standard 1.25" diameter male studs with 0.50" diameter cross-pin holes are provided. Special adapters can also be supplied at modest additional cost. Another option is the addition of alignment rods and linear bearings to the standard fixture, as shown in the second photograph. This maintains mutual alignment of the halves of the fixture independent of the testing machine. The lower attachment is eliminated, the fixture resting unconstrained on the base of the testing machine. Alignment rods and linear bearings can be used with shorter span flexure fixtures as well, as shown in the following photograph.
The following photograph shows a special screw-adjustable Long Beam Flexure Test Fixture designed for both three- and four-point loading. The four-point loading configuration is shown here.
Screw-Adjustable Long Beam Flexure Test Fixture Shown in the Four-Point Loading Configuration
The same fixture is shown in the next photograph, now configured for three-point loading. The loading beam has been turned upside down, to get the four-point loading heads out of the way. The adapter has been replaced by the three-point loading head, the adapter now being mounted on the other side of the beam.
Screw-Adjustable Long Beam Flexure Test Fixture Shown in the Three-Point Loading Configuration A special long beam flexure test fixture, designed specifically for reversed cycle fatigue loading, is shown in the next photograph. The specimen is clamped between the loading and support points so that reversed loading will be possible. These clamps rotate in the bearings shown. Both the loading and the support span lengths are adjustable.
Special Reversed Cycle Fatigue Long Beam Flexure Test Fixture
Other
specialized configurations of sandwich panel, short and long beam,
and solid laminate flexure test fixtures are also available, some
being shown elsewhere in this catalog. 1) 1) ASTM Standard C 393-00, "Flexural Properties of Flat Sandwich Constructions," American Society for Testing and Materials, West Conshohocken, Pennsylvania (first issued in 1957). 2) 2) ASTM Standard D 790-03 (2003), "Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials," American Society for Testing and Materials, West Conshohocken, Pennsylvania (first issued in 1970). 3) 3) ASTM Standard D 6272-02 (2002), "Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials by Four-Point Bending," American Society for Testing and Materials, West Conshohocken, Pennsylvania (first issued in 1998).
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