FED-STD-228A
Method 3171.1
18 APRIL 2014
TENSILE STRENGTH, VARNISHED CLOTH INSULATION
1. SCOPE
1.1 This method is intended for use in determining the tensile strength of cloth tape insulation. It is
particularly applicable to varnished cloth tape.
2. SPECIMEN
2.1 Unless otherwise specified in the detail specification, the specimen should be a piece of the
varnished cloth at least 14 inches in length and 1 inch wide, or full width if less than 1 inch, taken from a
single tape (layer) of the inspection unit.
3. APPARATUS
3.1 The apparatus shall be as follows:
3.1.1 A testing machine which meets the following requirements:
3.1.1.1 The machine shall be power-driven.
3.1.1.2 The applied tension shall be indicated by a dial, scale, or automatic recorder to within ± 2 percent
up to and including 50-pound load and to within ± 1 percent for over 50 pounds.
3.1.1.3 The indicator shall remain at the point of maximum force after rupture of the specimen.
3.1.1.4 The rate of travel of the power-actuated grip shall be 12 ± 0.5 inches per minute and shall be
uniform at all times.
3.1.1.5 The machine, when used for a given specimen, should be of such capacity that the maximum
load required to break the specimen is not greater than 85 percent nor less than 15 percent of the rated
capacity.
3.1.1.6 Grips. The face of each jaw of each grip shall measure 1 inch by 2 or more inches, the long
dimension being perpendicular to the direction of application of force. The jaws shall have smooth, flat
faces with edges slightly rounded to prevent cutting of the specimen.
4. PROCEDURE
4.1 At least 14 inches of each tape (layer) shall be removed from the inspection unit. Unless otherwise
specified in the detail specification, 10 percent of the tapes but in no case less than 5 tapes shall be
drawn at random for test from each inspection unit.
4.2 Unless otherwise specified in the detail specification, the specimen shall be conditioned for 46 hours
at a temperature of 23° ± 1°C. (73.5° ± 2°F) and a relative humidity of 50 ± 4 percent.
4.3 The thickness of the specimen shall be determined as described in method 1051 and the minimum
value obtained recorded as T.
105
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