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Analysis of plate-twist test plane shear modulus of composite materials.

Sims, G D; Nimmo, W; Johnson, A F; Ferriss, D H (1994) Analysis of plate-twist test plane shear modulus of composite materials. NPL Report. DMM(A)54

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In this report an improved analysis of the plate-twist test for the measurement of in-plane shear modulus of composite materials and the shear modulus of isotropic materials is described and experimentally validated. The analysis removes errors connected with the position of the loading points and allows greater freedom in their positioning. In particular it is no longer necessary to position the loading points exactly on the comers of the plate. An error of 1.0 mm in the positioning of the loading points on a 150 mm square plate results in an error of 3.4% in the measured shear modulus.
The main advantages of this test method are the simple flexure mode of loading, the simple specimen preparation, the large displacements at low loads (allowing use of crosshead movement to measure displacement), the ease of use at elevated or reduced temperatures and the uniform shear stress distribution. The method is not suitable for the measurement of shear strength. The test has been applied to a range of materials, with recorded shear modulus values ranging from 0.3 GPa to 88 GPa.
The method also has advantages in its use of a plate specimen for both injection moulded material, where it is more representative of a moulded product, and for advanced prepreg laminates, where a test panel is frequently fabricated for preparing the test specimens. In both cases the low applied strains suggest the plate can be re-used in further tests. The test method is also shown to be suitable for isotropic sheet materials.
A draft standard has been produced for this test method, which will be used in a round-robin exercise to obtain precision data. The existing standards for the use of this method to measure the shear modulus of wood products, will be checked, as they may have similar sources of error to those evaluated in this report.

Item Type: Report/Guide (NPL Report)
NPL Report No.: DMM(A)54
Subjects: Advanced Materials
Advanced Materials > Mechanical Measurement
Advanced Materials > Composites
Last Modified: 02 Feb 2018 13:19
URI: http://eprintspublications.npl.co.uk/id/eprint/164

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