A-A-1899
The longitudinally compressed material shall have the capability of expansion (decompression) to not less than 4.8 times its length without rupture of the plies. The longitudinally compressed material shall be measured for length in the compressed state.
For the longitudinally compressed material, expansion shall be determined by placing a sample (roll or multifold unit) on a level surface, unroll or unfold and measure the entire length in the compressed state. Cut a 4- by 14-inch specimen and suspend it from a clamp having flat faces 2 by 4-inches or greater. At a distance of 10 inches (accurately measured) attach another clamp similar to one above and either add sufficient weight or pull down by hand to its maximum distance without rupture of plies. Measure accurately the expanded length of the specimen between the clamps. Calculate the expansion as follows:
Expansion =
expanded length
compressed length
The width of the roll shall be as specified with a tolerance of plus or minus 3 percent or 1/4 –inch, whichever is larger. The width of the unrolled rolls shall be the average of four measurements. For longitudinally compressed material, perforations are cut out areas leaving one inch linkages along the width to permit the tearing off of a premeasured length of material.
Measured thickness.
The measured thickness of the material shall be not less than 85 percent of the specified thickness.
Place a stack of 4-inch square (+ 1/8 – inch) samples of material which is at least 1 inch high on a level surface. If sample is 1 inch thick or greater, one sample is sufficient. Place a 6-inch square flat weight plate which weighs 0.4 + 0.005 pounds on top of this stack. After 1 minute, measure the vertical distance (thickness) between the level surface and the weight plate at each four corner and record the average (final thickness). The average of the four measurements shall be the measured thickness. (Note: If more than one piece of material is used, the measured thickness shall be the final thickness divided by the number of pieces). The percent of specified thickness (as specified in the contract) shall be calculated as follows:
Percent of specified thickness = (measured thickness) X 100
(specified thickness)
Strain limit. The strain limits of the material shall be not less than 50.0 nor more than 75.0 percent when tested as follows:
Place a sample(s) of material to form a stack of 4-inch square (= 1/8-inch) material at least 1-inch high. If sample if 1-inch or greater, one sample, is greater. Measure the height (measure thickness) of this stack. (Note: for the purpose of this test, if each sample is less than 1-inch in measured thickness, the measured thickness of the stack and not the individual samples is used.) Place a 3 p.s.i. load on this stack for 15 seconds. Measure the loaded height at the four corners and record the average (compressed thickness). The strain shall be calculated as follows:
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