Shear Testing
Here we will see measurement of in-plane shear modulus  only. The methods are listed below:
- Tension of a
 laminate
- Tension of an off-axis lamina
- Torsion of a unidirectional tube
- Iosipescu shear of unidirectional laminae and cross ply laminates
- Rail shear of unidirectional laminae
- Picture frame test
1. Tensile Test:
A tension test on laminate is popularly used test for the measurement of in-plane shear modulus . The more details of this test are available in ATSM standard D3518/D3518/M–91. According to ASTM standard the method uses a 250 mm long rectangular specimen with width 25 mm and thickness 2 mm. Further, it is recommended that for materials constructed with layers thicker than 0.125mm, the laminate should consist of 16 layers, that is,  .The specimen is shown in Figure 8.8. The dimensions in this figure are in mm.
When a is subjected to axial tensile stress  then stresses in principal material coordinates developed in each of the  and  lamina are given as
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(8.14) |
where,
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(8.15) |
and other quantities as defined in earlier chapters. For a special case with we get the shear stress as
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(8.16) |
Thus, from this equation one can see that the shear stress in principal material directions is statically determinate, that is, it is independent of material properties of the specimen and only depends upon the magnitude of the applied stress. The magnitude of this stress is half of the applied stress.
Figure 8.8: Specimen geometry and strain gage positioning for tensile testing |
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