Tensile testing machine

Fig. 2. Illustrations of forces to which adhesive bonds are subjected, (a) A standard lap shear specimen where the black area shows the adhesive. The adherends are usually 25 mm wide and the lap area is 312.5 mm. The arrows show the direction of the normal apphcation of load, (b) A peel test where the loading configuration, shown by the arrows, is for a 180° peel test, (c) A double cantilever beam test specimen used in the evaluation of the resistance to crack propagation of an adhesive. The normal application of load is shown by the arrows. This load is appHed by a tensile testing machine or other...

The principal type of shear test specimen used in the industry, the lap shear specimen, is 2.54 cm wide and has a 3.23-cm overlap bonded by the adhesive. Adherends are chosen according to the industry aluminum for aerospace, steel for automotive, and wood for constmction appHcations. Adhesive joints made in this fashion are tested to failure in a tensile testing machine. The temperature of test, as weU as the rate of extension, are specified. Results are presented in units of pressure, where the area of the adhesive bond is considered to be the area over which the force is appHed. Although the 3.23-cm ... 

Peel tests are accompHshed using many different geometries. In the simplest peel test, the T-peel test, the adherends are identical in size, shape, and thickness. Adherends are attached at thek ends to a tensile testing machine and then separated in a "T" fashion. The temperature of the test, as well as the rate of adherend separation, is specified. The force requked to open the adhesive bond is measured and the results are reported in terms of newtons per meter (pounds per inch, ppi). There are many other peel test configurations, each dependent upon the adhesive appHcation. Such tests are well described in the ASTM hterature. 

Slides Slab and sheet metal rolling extrusion, etc., of polymers tensile-testing machines hardness-testing machines hardness indentations. 

Tensile testing machine operated in a controlled temperature and humidity environment. Many applications involve bonding paper, which exhibits properties that are highly dependent on humidity. In addition, adhesive Tg values are often close to room temperature, and thus properties change substantially over even a few degrees. Therefore, for reproducible comparisons, temperature and humidity control is necessary. 

Fig. 8.101 Bend lest using a tensile testing machine (after Beck et al. )...

Mechanical Property Testing. Mechanical tests were performed on both unirradiated and irradiated materials at -157°C, 24°C, and 121°C. Specimens were kept dry prior to testing in an environmental chamber mounted in a tensile testing machine. Tensile test specimens of [0]4, [10]4, [45]4, and [90]4 laminates were cut from 4-ply composite panels. All specimens were straight-sided coupons. For tension and shear tests the length/width aspect ratio was 8. For the compression tests the aspect ratio was 0.25 and the unsupported length was 0.64 cm. The [0]4 laminates were used to measure the ultimate tension and compression strength, Xit the axial... 

FIGURE 15.33 A schematic of a hydraulic tensile testing machine. 

The trapezoid test method (ASTM Dll 17) is recommended for determining the tear resistance of nonwoven fabrics. An outline of a trapezoid is marked on a 7.5 x 15 — cm specimen, and the nonparallel sides are clamped in the jaws of the tensile-testing machine. The load is applied to the specimen in such a way that the tear propagates across the specimen width. The value of the breaking load is obtained from the load—elongation curve and is determined primarily by the bonding or interlocking of the fibers of the composite structure. 

A series of six stress-strain cycles with a crosshead rate of 600 mm/min was applied to specimens having a parallel length of 25 mm and a cross-section of 1 x 4 mm2 on a tensile testing machine. The samples were continuously stretched in six hysteresis cycles up to 60% of their elongation at break values, as shown in Fig. 47. This procedure is an established one and widely practiced for elastomeric composites reinforced with fillers such as carbon black and silica, which tend to build a strong filler-filler network [83]. 

In some ways modem tensile testing machines have reduced the need for a separate, particularly simple, routine control test. However, a test which is both simple in the sense of measuring one parameter and provides a relaxed modulus is intrinsically attractive. Such tests in various forms have existed for a long time but do not seem to have attained widespread popularity. A version in which a fixed stress is applied and the elongation after 1 min noted is given in ASTM D145689. A specific instrument developed for this... 

Tensile tests involve either stretching a sample and monitoring the load or loading it while monitoring the extension. The simplest test uses a tensile testing machine (e.g. an Instron) where the sample is stretched at a constant rate while the load is measured using a (usually hard) load cell. Variations on this test allow the specimen to be extended at a constant strain rate or to be loaded at a constant load, or stress rate. These latter tests are usually carried out on servo hydraulic machines. 

All these tests are in common use to measure the tensile stiffness of polymers. For example, tests at constant extension rate are often carried out on an Instron tensile testing machine. Tensile creep is used in many cases while stress relaxation is not so common. Dynamic testing is commonly performed using the Rheovibron or other commercial equipment32 or home made equipment33,... 

To determine the quantitative effects of this consolidation procedure, fabric disks cut from the extracted degraded fabric were used as substrates. These fabrics were torn on an Instron tensile testing machine as described earlier and patched with six applications of either the 0.1% dyed wood pulp or the 0.05% dyed Cellunier P slurry. The samples were then torn again on the Instron tester. The average breaking strengths and add-ons of the samples after six passes with slurry are reported in Table IV. A typical tom fabric and a patched fabric are shown in Figures 6 and 7. 

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