BS ISO 6721-6:2019 pdf download – Plastics – Determination of dynamic mechanical properties Part 6: Shear vibration – Non-resonance method 5.3 Temperature measurement and control According to ISO 6721-1. 5.4 Devices for measuring test specimen dimensions According to ISQ 6721-1. 6 Test specimens 6.1 General According to ISO 6721-1. 6.2 Shape and dimensions Various shear test specimen assemblies can be used. A suitable design is shown in Figure 2. Here the metal end-pieces P are cylindrical, but any cross-sectional shape is suitable as long as the end-pieces can be clamped rigidly in the shear load stage. The dimensions of the end-pieces and the polymer specimens S shall be chosen such that the deformation of the end-pieces under an applied load is negligible in comparison with that of the specimens. For a polymer whose shear modulus is less than 100 MPa, this will mean that the thickness of the end-pieces may be comparable with the thickness L of the specimens. The cross-sectional shape of the polymer specimens in the plane of their bonded faces is not critical, although a rectangular section is recommended in order to simplify the application of a term representing the contribution to the specimen deformation from bending. See Formula[1). The specimens are typically cut from a sheet of the polymer and bonded to the end-pieces to construct the shear test-specimen assembly. The dimensions of each polymer specimen shall not vary by more than 3 % of the mean value. This dimension shall be sufficiently large to allow adequate accuracy to be achieved in the determination of dynamic strain and hence dynamic moduli [see Formula (1]]. In addition, it is recommended that the dimension h of the polymer in the direction of the applied load should be greater than 4L in order to make the correction for bending negligible. NOTE A variation in dynamic properties can be observed between specimens of different thickness prepared by injection moulding owing to differences which can be present in the structure of the polymer in each specimen. 6.3 Preparation of polymer specimens According to IS0 6721-1. 7 Number of test specimens According to IS0 6721-1. 8 Conditioning According to IS0 6721-1. 9 Procedure 9.1 Test atmosphere According to ISO 6721-1. 9.2 Measuring the cross-section of the polymer specimen According to ISO 6721-1. 9.3 Clamping the test assembly Mount the test specimen assembly in the load stage using a clamping force that is...
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