Investigation of Defect Effects on Adhesively Bonded Joint Strength Using Cohesive Zone Modeling

Abstract

In this paper, effects of the defect in an adhesively bonded joint have been investigated using cohesive zone modeling. Consequently, a 3D finite element model of a single lap-joint is constructed and validated with experiments. Strength prediction of current model is found desirable. Accordingly, different sizes of square shape defects are imported to model in the form of changing (raised or degraded) material properties (heterogeneity) and locally delaminated areas (as inclusion/void), respectively. Joint strength is investigated and a stress analysis is carried out for adhesive layer and adherends. Obtained Results show that, defect has significant impact on the results. It is found that at constant size of defect, local delamination has more impact on bonded joint strength than the heterogeneity. Furthermore, stress analyses demonstrate that the stress field does not change in adherends by taking defects into account. However, stress values decrease with degraded material properties and joint’s strength. Through evaluation of peel and transverse shear stresses in adhesive layer it is found that there is a change of stress distribution for both types of defects. Whereas, there is a considerable stress concentration in the delaminated adhesive layer.

A practical strategy to identify appropriate application patterns for adhesively bonded joints

“…Ideally, corners should be completely filled, no air should be trapped and not too much adhesive runs out. This is important because incomplete filling may reduce the strength of the joint [1,2] and adhesive leakage is a waste of valuable raw materials and causes unnecessary cleaning.…”

How to Find the Perfect Application Pattern for Adhesively Bonded Joints?

“…It is desirable to produce a bonded joint where the adhesive fills the gap completely, with no air entrapment and as little adhesive wastage due to overflow as possible. Both requirements are considered fundamental for the reliability of any bonded joint (Ratsch et al, 2019;Majid and Mohammad Reza, 2018). Accordingly, in most safety relevant situations, the gap is therefore often heavily overfilled so to ensure uniform filling, which comes at the cost of significant adhesive waste and additional work steps to remove the overflow.…”

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