Thick adherend shear test

Rg. A6. Thick adherend shear test (TAST) specimen. 

BSl (2011), BS EN 14869-2 2011 Structural adhesives. Determination of shear behaviour of structural bonds. Thick adherends shear test, 2011 edn. London British Standards Institution. 

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The elastic limit can be established by using the thick adherend shear test to determine the stress/strain relationship. This test uses steel adherends which are so thick that under the test conditions, their distortion is small and the influence on the data is acceptably low. A typical curve is shown in Fig. 10. 

The thick adherend shear test also provides data on the modulus of the adhesive. If we use this data along with a knowledge of the modulus and thermal expansion of the two materials being bonded together, it is possible to compute the stress levels experienced by a simple lap joint. 

To overcome these problems of interpreting the results from such test geometries several different approaches have been adopted. Firstly, several workers [8-10] have used the thick-adherend shear-test specimen (Section 6.4.2) to obtain dynamic fatigue data which are more characteristic of the actual adhesive employed. Such data may, therefore, be used to rank various adhesive formulations and, possibly, to predict service life. 

First, we must (with one exception) disqualify as shear tests the single-lap joint and its allies described earlier. The exception is the thick adherend shear test. As discussed above, provided proper precautions are taken, this test can be used to determine the shear properties of an adhesive, although the ultimate strength cannot be attained (para. 4.2 of ASTM D 3983-81). 

The tensile and compressive properties were obtained in the bulk form and the shear properties were obtained with the thick adherend shear test (TAST). ( , Young s modulus Cy, yield strength strength tensile failure strain ly, shear yield strength shear strength jy, shear failure strain v, Poisson s ratio)... 

One can argue that the adhesive properties measured in a joint are more representative. Furthermore, the fabrication and testing procedure is relatively simple, especially for the case of the thick adherend shear test (TAST). However, the main disadvantage is the need for high-precision measurement devices due to the low adhesive displacements. In many cases. 

Thick adherend shear test fTAST) extensometer... 

Pinto AMG, Magalhaes AG, Campilho RDSG, da Silva LFM, Chousal JAG, Baptista APM (2010) Shear modulus and strength of an acrylic adhesive with the notched plate method (Arcan) and the thick adherend shear test (TAST). Mater Sci Forum 636-637 787... 

An insight into the performance of real bonded structures may only be obtained from knowledge of the engineering characteristics of the adhesive concerned and their interaction with a mathematical model of the structure itself The appropriate characteristics — shear modulus, elastic shear stress limit, asymptotic shear stress — are probably best obtained from the thick adherend shear test . Typical figures for two contrasting types are given in Table 7.3. 

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