Dean, G; Crocker, L E (1999) Project PAJ2. Report No 10. A proposed failure criterion for tough adhesives. NPL Report. CMMT(A)158

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Abstract

Tensile tests on bulk specimens and butt-joint specimens of adhesives have been used to develop a criterion for ductile failure based on a critical level of strain. Earlier work on butt-joint specimens loaded in torsion has indicated that adhesives can tolerate large shear strains without failure. It was concluded that a significant level of volumetric (dilatational) strain is therefore needed to cause failure, but the results of the tests reported here show that the critical level is dependent upon the magnitude of the associated shear component.
A criterion is proposed that is consistent with the failure strains obtained from the above tests on an epoxy and an acrylic adhesive. Further work is now needed to investigate whether the criterion can be used to predict when failure will occur in joint test specimens of different geometry. To achieve this, it is necessary to use finite element methods to accurately predict the strain level and strain state in the region of the adhesive layer where failure initiates. Experience with the application of these methods to the stress analysis of the butt-joint specimen loaded in tension and other joint test specimen geometries has revealed that strains cannot be confidently predicted with adequate accuracy. It is concluded that a new materials model needs to be developed for adhesives.

Item Type:	Report/Guide (NPL Report)
NPL Report No.:	CMMT(A)158
Subjects:	Advanced Materials Advanced Materials > Adhesives Advanced Materials > Polymers
Last Modified:	02 Feb 2018 13:18
URI:	http://eprintspublications.npl.co.uk/id/eprint/1101

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