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Methods for obtaining volumetric coefficients for hyperelastic modelling of the flexible adhesives.

Crocker, L; Duncan, B C (2001) Methods for obtaining volumetric coefficients for hyperelastic modelling of the flexible adhesives. NPL Report. CMMT(A)286

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In the Performance of Adhesive Joints extension project ‘Flexible Adhesives’ (PAJex2) a selection of hyperelastic material models are under investigation to determine the suitability of these models for predicting the behaviour of a flexible adhesive in bonded structures. Many flexible adhesives cannot be assumed to be incompressible, as Poisson’s ratios are often lower than 0.5 (the case for incompressibility). Hence the compressibility of the material should be included in the model predictions through the volumetric terms in the hyperelasticity equations.
Three methods for obtaining volumetric properties data suitable for incorporation into the hyperelastic models have been investigated. These methods were volumetric compression, uniaxial tension and butt tension. A testing jig has been designed and manufactured in-house to measure the volumetric compression of adhesives. Jig design, specimen preparation and volumetric compression testing have been described. Methods for calculating volumetric compression data have been obtained.
It is felt that properties in tension are critical to joint failure and that volumetric behaviour in tension may be more suitable as input data. Details of methods for obtaining volumetric properties from both butt tension and uniaxial tension experimental measurements are presented. It has been found that, although the volumetric tensile data has more of an effect than volumetric compression data, FE predictions incorporating the volumetric term fail to offer significant improvements over those made without the volumetric term. Of the three methods investigated, the uniaxial tension method is the most practical method for obtaining volumetric properties since these measurements are also required for obtaining other material coefficients.

Item Type: Report/Guide (NPL Report)
NPL Report No.: CMMT(A)286
Subjects: Advanced Materials
Advanced Materials > Adhesives
Advanced Materials > Materials Modelling
Last Modified: 02 Feb 2018 13:17
URI: http://eprintspublications.npl.co.uk/id/eprint/1877

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