Angled test-piece

For angle test pieces with a nick added, the problem is essentially the same as with the crescent test piece. With unnicked angle test pieces, the essential requirement is the production of a reproducible re-entrant angle,... 

With crescent, Delft and angle test pieces only the maximum force reached is recorded, although the change of force along the short tear path could be obtained with a force measuring and recording system having very... 

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). 

For the angled test-piece, the tearing energy is given by ... 

Polysar) mode III tearing 1000-3000 Gill (for trousers and angled test pieces alike) increases with rate of crack growth (10-" [Pg.266]

When directed towards the test piece the laser beam passes through a centre hole in a 45 degree fixed-angle mimor. Between this mirror and the test piece the laser beam and the flourescence follow a common beam path. A photodetector is aimed at the 45 degrees angle mirror and, therefore, looks along the laser in this common beam path, see Fig 3. 

The position and angle of the test pieces to the sun (for both radiation and temperature) is important. A wide range of exposure methods and angles are available at most test stations. The more conventional and widely used are ... 

ISO 34-1 2004 Rubber, vulcanized or thermoplastic - Determination of tear strength -Part 1 Trouser, angle and crescent test pieces... 

You may need to play around with the drops for a while in order to see the differing affinities that the bag and wrap have for water. One way to do this is to tape the polymers side by side stretched out on a sturdy piece of cardboard. Tilt the cardboard to various angles, testing for the speed with which water drops roll down the incline on the two surfaces. Ultimately, you should find that the drops roll more slowly on the wrap (polyvinylidene chloride) than on the bag (polyethylene terephthalate). The source of this greater stickiness in the wrap is the fairly large chlorine atoms of the polyvinylidene chloride. 

Dynamic mechanical analysers, as discussed in chapter 9, can be constructed so that they can be used with unvulcanised materials and, hence, the in phase and out of phase components of modulus and the loss angle measured. The usual test piece geometries for cured rubbers are not convenient for the uncured materials where some form of oscillating shear is probably the best approach. This is the geometry used in cure meters discussed in the next section and such instruments have formed the basis for apparatus which measures dynamic properties from before and through the curing process. 

Method A is examination at 30x magnification with a binocular microscope and an optional camera. Illumination is at an oblique angle of 30° to accentuate the surface detail. The test piece is cut by a razor blade and vulcanized or unvulcanised material can be used. In the latter case, the sample is first compressed to minimize trapped air and the blade is heated. Warning is given that the result may not be the same as when using a vulcanized test piece. The result is compared to a set of standard photographs that are given in the standard. 

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 Laboratory Abrasion Tester 100 (LAT 100)65 uses a wheel test piece on an abrasive disk geometry so is the type (d) of Figure 11.4. The abrasive disk is driven and the speed, contact force and the slip angle of the test piece can all be varied. What makes this apparatus so different from all the others is not only the versatility but the sophistication of the instrumentation and the computer control. This means that it can be used to obtain data as a function of several parameters and combine results to make predictions of wear for the extremely complicated service conditions of tyres. Not surprisingly, it is very expensive and unlikely to be used on a routine basis outside of tyre companies. Nevertheless, is has now been proposed for standardization in ISO TC 45. 

ASTM has also standardised a flipper type of machine7 which uses grooved and pierced test pieces to measure crack growth. The gap between the revolving disk and the deflector bars can be varied so that the angle of deflection and, hence, the severity of test can be varied. The apparatus in contained in an oven so that tests can be made over a range of temperatures. 

The basic method is a closely specified test intended for quality control or the comparison of bonding systems, but could readily be extended to investigate the effects of test piece dimensions, peeling angle, test speed, etc. 

A "tension" method using conical metal end pieces is standardised in ISO 460011. BS 903 Part A4012 is identical and ASTM D429, Method C3 is very similar. The test piece diameter is 25 mm and the cone angle 45° but the distance between the tips of the cones is 12 1 mm in ISO and 11.5 1.2 mm in ASTM. An earlier draft of ISO 5600 had the tolerance as 0.1 mm which perhaps implies that this dimension is critical. The grip separation rate is 50 mm/min (or 0.83 mm/s in ASTM) and the result is simply expressed as the maximum force recorded. 

The angle between the two gripped legs of the test piece is nominally 180° (see Figure 18.2). The plies should separate at a sharp angle but this will depend on the thickness and stiffness of the plies. The standard suggests... 

There are three main configurations for the tear test. In the first two a tensile force is applied to the sample. In one configuration, the force is vertical to the plane of the sample, and in the second it is at right angles. In the third style, an element of shear is also introduced. Figure 9.3 shows the basic configuration of the tear test pieces. 

Part 1 Trouser, angle, and crescent test pieces Part 2 Small (delft) test pieces Standard test method for tear strength of conventional vulcanized rubber and thermoplastic elastomers Testing of rubber and elastomers Determination of the tear strength of elastomers Trouser test piece... 

Physical testing of rubber part A3 Determination of tear strength [trouser, angle, and crescent test pieces Section 3.2 Small (Delft) test pieces... 

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