TROUSER TEAR TEST

Using trouser tear tests, Gent and Tobias [21] showed that the Lake-Thomas model held reasonably well for a number of elastomers. In their analysis, they took the molecular mass of a strand as that extracted from the elastic modulus and thereby incorporated the effect of entanglements (Section 9.8.2). More recent results on poly(dimethyl siloxane) (PDMS) elastomers using simple shear tests [22,23] over a wide range of structure (extent of cross-links and trapped entanglements) indicate that the role of entanglements in elastomer fracture needs to be elucidated further. 

The quantity directly measured in a tear test is the force on the test piece during testing. Particularly with the trouser method, this force will fluctuate along the tear path. ISO 34 takes the maximum force reached in the case of crescent, angle and Delft methods but for the trouser method a median force is determined in accordance with procedures given in ISO 6133147, Analysis of multi-peak traces obtained in determinations of tear strength and adhesion strength. 

The two most commonly specified tests are the Die C test and the "trouser tear" (D470) test. Both of these tests measure resistance to tear propagation. Other test shapes include the crescent tear with or without end tabs. This sample shape is often nicked. The "Delft" (IS0816) sample with its internal nick is often used from samples taken from finished products. The exact size of the nick does not appear to be critical to the result. 

The standard calculation is based on the force required for the tear (in Newtons) divided by the thickness of the sample in millimeters. When carrying out the trouser tear, the median force must be taken, as the load varies during the test. 

Russian State Standard 14236-81. Polymer Films. Tensile Testing Method. ISO 6383-1 1983. Plastics - Film and Sheeting - Determination of Tear Resistance - Part 1 Trouser Tear Method. 

Most of the normal tear tests are carried out using a tensile machine with suitable grips. The tearing force can rise rapidly, and in trouser type tests it can rise and fall during the... 

ISO 34 (BS903, Part A3) contains as many as five test methods for tear strength, a reflection not only of the general importance of the property but also of the difficulty of matching laboratory tear tests to product behavior. The methods comprise the trouser, crescent. Delft, and nicked and unnicked angle test pieces, none of which gi es comparable results to another. ASTM D624 specifies crescent test pieces with and without tab ends (Dies A and B respectively), the unnicked angle test piece (Die C). and the trouser test piece (Die T). 

Good agreement has been reported between tearing energies derived from the test and those from trouser tear measurements [18]. 

Figure 5.2 DUferent types of tear test-pieee geometry (a) trouser, (b) pure shear, (c) angle and (d) split tear test-pieces.

It reduces the problems of forking as experienced with other common test-pieces such as parallel tensile strip, pure shear and trouser tear. 

In shear measurements, bimodal PDMS networks showed large upturns in the pure-shear modulus at high strains, similar to those reported for elongation and biaxial extension. Tear tests were carried out on bimodal PDMS elastomers, using the standard trouser-leg method. Tear... 

The other methods include ISO standard method. Tear properties of fabrics — Part 2 Determination of tear force of trouser-shaped test specimens (Single tear method) (ISO 13937-2 2000). 

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