Dean, G D; Crocker, L E (2001) Analysis of joint tests on an epoxy adhesive. NPL Report. MATC(A)40

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Abstract

The results of studies of deformation and failure of lap-joint and scarf-joint specimens are reported. The location in the lap joint at which failure initiates has been traced to a region of the bond interface near the end of each adherend. Finite element analyses of the specimen with the adhesive progressively detached from the adherend in this region show that these cracks significantly reduce the load bearing capability of the joint. This explains the departure of measured and predicted force/extension curves for the specimen described in previous reports where no account of premature cracking had been included in the predictions.
A strain-based failure criterion, proposed in earlier work, is seen to be broadly consistent with the onset of failure in the lap-joint specimen. However, calculated strains in a scarf-joint specimen at failure are substantially above those at which failure is predicted by this criterion. The calculated strain levels and distribution are however shown to be sensitive to the model used to describe deformation in the adhesive.
An alternative failure criterion is explored based on a critical level and state of stress at the interface with the adherends. A proper evaluation of any failure criterion is not possible without accurate predictions of stresses and strains in the region of failure initiation. The accuracy of analyses using available materials models in finite element systems is uncertain and these studies should therefore be continued when the new cavitation model has been successfully implemented in ABAQUS.

Item Type:	Report/Guide (NPL Report)
NPL Report No.:	MATC(A)40
Subjects:	Advanced Materials Advanced Materials > Adhesives
Last Modified:	02 Feb 2018 13:17
URI:	http://eprintspublications.npl.co.uk/id/eprint/2711

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