Duncan, B C; Crocker, L E; Urquhart, J M (2000) Evaluation of hyperelastic finite element models for flexible adhesive joints. NPL Report. CMMT(A)285

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Abstract

A comprehensive evaluation, covering a range of strain rates and temperatures, has been undertaken into the applicability of hyperelastic material models in Finite Element (FE) packages for predicting the force-extension response of lap joints bonded using a flexible adhesive. Comparisons between measured and predicted lap joint responses have indicated that, for the adhesive studied, the FE models have poor accuracy. Many modelling and experimental factors that were thought to influence the accuracy of the predictions were investigated. The findings suggested that the models do not properly describe the adhesive material. However, there is a suspicion that the adhesive studied may not be representative of all flexible adhesives. A number of tools and statistical procedures have been developed in this study that can be used to validate further adhesives or models.
Some key findings were made regarding the provision of input material properties data and the performance of the FE modelling. It was found that using uniaxial tension and volumetric tests only to obtain the input data gave the best general quality of predictions. It would seem that the expensive planar and biaxial tension tests could be omitted without compromising accuracy. A method for obtaining volumetric properties from uniaxial tension tests has been described. Generalised plane strain elements were found to be better for representing the adhesive layer than standard plane strain elements.
The results point towards simpler, lower-order models such as Neo Hooke and Arruda-Boyce being better at representing the adhesive than more complex, higher-order models. The simpler models have the additional advantages that trends in the strain rate and temperature dependence of the fitted model coefficients can be predicted. Analysis of the stress distributions at the maximum loads sustained by the joints shows that peak values of peel stress and von Mises stress are comparable with the ultimate tensile stresses obtained for bulk test specimens. Thus, stress components may be suitable as failure criteria.

Item Type:	Report/Guide (NPL Report)
NPL Report No.:	CMMT(A)285
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/1796

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