Taber Stiffness Testers

• Data

  Range	Stiffness Units	Sample Length	Roller Position	Sample Size	Range Weight	Angle of Deflection	Scaling Multiplier
  1	0 - 1	2cm	SR Attachment	1.5" x 1.5"	10 Unit Compensator	15°	0.01
  2	0 - 10	1cm	Up	1.5" x 1.5"	10 Unit Compensator	15°	0.1
  3	10 - 100	5cm	Down	1.5" x 2.75"	---	15°	1
  4	50 - 500	5cm	Down	1.5" x 2.75"	500 Unit	15°	5
  5	100 - 1,000	5cm	Down	1.5" x 2.75"	1,000 Unit	15°	10
  6	200 - 2,000	5cm	Down	1.5" x 2.75"	2,000 Unit	15°	20
  7	300 - 3,000	5cm	Down	1.5" x 2.75"	3,000 Unit *	15°	30
  8	500 - 5,000	5cm	Down	1.5" x 2.75"	5,000 Unit *	15°	50
  9	1,000 - 10,000	5cm	Down	1.5" x 2.75"	5,000 Unit *	7 1/2°	100

  * Auxiliary Range Weight Set (range 3,000 - 5,000 Taber Units) is sold separately and required for ranges 7 - 9.

To allow the testing of materials with different stiffness properties, range weights can be applied to the pendulum.  For extremely light weight materials, a compensator range weight is mounted to the top of the pendulum.  Range weights of 500, 1000 and 2000 "Taber Units" are mounted to the bottom of the pendulum and required for stiffer materials.  An optional range weight set of 3000 and 5000 Taber units is required for test ranges 7, 8 and 9.

Range 1 is used with Taber's optional Sensitivity Range Attachment (also referred to as SR or High Sensitivity Attachment) to test extremely lightweight and flexible materials whose Taber Stiffness Unit value are between 0 - 1.  Examples include cellophane, natural fibers and synthetic filaments, tissue paper, metallic foils, films, etc.  The attachment includes two parts, the Driven Pins Holder which is secured between the clamp jaws, and the Driving Pins Holder which is mounted to the studs in place of the left- and right-hand rollers.  Both parts include precision pins that are oriented horizontal to the face of the V-5 Stiffness Tester. A specimen 1 1/2" x 1 1/2" is mounted such that the second and fourth pins are above the specimen.  As the driving disc rotates, the fourth pin of the Driving Pins Holder pushes down on the specimen while the first pin pushes up.  As the sample is deflected, the Driven Pins Holder aligns the pendulum to the appropriate stiffness value.  For Range 1, the specimen is only deflected to the right.

Many customers have also utilized the Taber V-5 Stiffness Tester to evaluate wire and cable stiffness characteristics. The tester now incorporates a "v-notch" in the clamps to accommodate this testing. Suggested samples are 70mm long and 3mm - 8mm in diameter, and centered in the notch with care so as to not pinch or crimp the sample. For wire and cable samples less than 3mm diameter, it is recommended to secure the sample at a location in the flat region of the clamp.  Samples with curvature may interfere with proper set-up and function of the Stiffness tester and should be avoided. In addition, test results obtained should be used for comparison only - that is, between lots, between materials, etc.

Evaluation

After the test material has been deflected 15° (or 7 1/2°) to the left and right, the average reading is determined.  This is then multiplied using the number assigned in the Set-Up Chart for the particular range.  The product is the stiffness value of the material measured in Taber Stiffness Units.

Taber Stiffness Units are defined as the bending moment of 1/5 of a gram applied to a 1 1/2" wide specimen at a 5 centimeter test length, flexing it to an angle of 15°.  A Stiffness Unit is the equivalent of one gram centimeter.

E = 0.006832 • (1/(w • d3 • θ)) • ST

Where E = Stiffness in flexure in pounds per square inch

            w = specimen width in inches

            D = specimen thickness in inches

            θ = deflection of specimen converted to radians (15° = 0.2618 radians, 7.5° = 0.1309 radians)

            ST = Taber Stiffness Units

Resilience is the elastic quality of a material expressed as the ratio of basic stiffness to initial stiffness, as determined with the following formula:

          % of Resilience = (Basic Stiffness • 100) / Initial Stiffness

Initial Stiffness is the first reading obtained immediately when flexing the specimen to the end point of deflection (typically 15°), and is generally used for comparing relative stiffness qualities.

Basic Stiffness is the loss of stiffness caused by "elastic fatigue", or the realignment of the molecules experienced by the material when a specimen is held at the end point of deflection.

As reported in TAPPI Test Method T543, Taber Stiffness Units can be converted to Genuine Gurley™ Stiffness Units with the below equation.  The range of correlation test studies between Taber and Gurley stiffness values were from 20 - 150 g cm on Taber.

ST = 0.01419SG - 0.935

Where ST = Taber Stiffness Units

            SG = Gurley Stiffness Units

To convert Taber Stiffness Units to Millinewton-Meters, use the following equation:

"X" mN-m = ST • 0.098067

Where ST = Taber Stiffness Units

To convert Taber Stiffness Units to Pound-Inch, use the following equation:

"X" lb-in = ST • 0.000868

Where ST = Taber Stiffness Units

The extreme sensitivity of the Taber V-5 Stiffness Tester magnifies variations in the material.  Therefore, it is recommended that 5 or more samples be tested and the average result taken as the stiffness rating.  Variations in testing may also result from the way in which the specimen is clamped or how clearances are adjusted between the rollers and specimen.  It is important to note:

• Do not flex a sample prior to testing
• Be careful not to crush the sample by over tightening the clamps
• Excessive compression of the sample will reduce the material's thickness thereby resulting in stiffness readings that are both inconsistent and inaccurate due to a reduced cross-sectional area at the clamp

Some materials have an inherent grain derived from their manufacturing process.  This will typically affect the stiffness and must be accounted for during the test procedures by testing those samples in both directions.  It is advisable to prepare and test 5 to 10 specimens in each grain direction for testing.

• Compensator Range Weight
• Taber Unit Range Weights 500, 1000, 2000
• Calibration Specimen