Poker chip test

Triaxial tests usually involve more elaborate testing equipment and more precise measuring techniques than those normally used for uniaxial and biaxial measurements. In the poker chip test (33, 59) the faces of a thin circular disc are bonded to rigid plates (Figure 18). The speci-... 

Figure 18. Poker chip test assembly with indicated instrumentation...

Refinement of the poker chip test to include a center load cell in one of the bonded plates is reported by Harbert 40). Figure 19 shows the stress-strain curves generated by external measurement as well as the failure point determined by the center load cell. 

Figure 19. Poker chip test data. Small center load cell in one of the bonded plates provides an indication of the rupture point which would not be obvious from over-all load recording instruments (40)...

Sometimes called the poker chip test.) This is effectively a butt joint to which tensile loads are applied, as shown in Fig. 81(a). At first sight, this appears to be a simple test in which the adhesive is loaded uniformly in tension. Unfortunately, this is far from the case. If the adhesive layer were thick (i.e. many times its lateral dimensions) as... 

Fig. 81. Tensile butt joint tests (a) poker chip test (thin adhesive film) (b) and (c) schematic for thick adhesive test (d) gauge length and deflections in...

In a recent attempt to bring an engineering approach to multiaxial failure in solid propellants, Siron and Duerr (92) tested two composite double-base formulations under nine distinct states of stress. The tests included triaxial poker chip, biaxial strip, uniaxial extension, shear, diametral compression, uniaxial compression, and pressurized uniaxial extension at several temperatures and strain rates. The data were reduced in terms of an empirically defined constraint parameter which ranged from —1.0 (hydrostatic compression) to +1.0 (hydrostatic tension). The parameter () is defined in terms of principal stresses and indicates the tensile or compressive nature of the stress field at any point in a structure —i.e.,... 

Despite the fact that adhesive joints are rarely designed to be loaded directly in tensile mode, tensile tests are eommon for evaluating adhesives. The axially-loaded butt (or poker chip ) joint geometry, as recommended by ASTM D897(52), is depicted in Fig. 4.11. 

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