QUALIFY project presented at the 5th international conference on structural adhesive bonding AB2019 on 11-12 July 2019 in Porto, Portugal.

Dr. Mohamed Nasr Saleh (one of the SI&C team members at TU Delft) presented the QUALIFY project generally to a wide range of adhesion and adhesives experts from all over the world, and specifically the recent work done on understanding the mechanics and stress state of double-lap bi-material joints bonded with thick adhesive. The quality of the work was well appreciated by the conference committee to the extent it was invited for a full journal publication in a special issue in the international journal of adhesion and adhesives by Elsevier.

The abstract of the presentation and the paper is detailed below:

Mechanics of double-lap Steel-to-CFRP adhesively-bonded joints loaded in tension are investigated experimentally using Digital Image Correlation (DIC) and Acoustic Emission (AE), analytically using a one-dimensional closed-form solution and numerically with Finite Element analysis. The double-lap bi-material joints are fabricated of a steel core adhesively bonded to two CFRP skins with adhesive thickness of ~ 8 mm, using an Epoxy-based and MMA-based adhesives. In order to capture the in-plane deformation of the joint, full field strain/displacement maps are obtained using DIC. This data is used to validate the shear-lag model predictions of the adhesive shear stress/strain distribution as well as the linear-elastic Finite Element Model (FEM) results. In addition, they are used to capture the susceptible damage locations and their effect on the displacement contour maps, strain distribution and load transfer between the joint’s different constituents.  A correlation between the DIC displacement and the AE signals is obtained for damage detection in both joints. Moreover, a good agreement amongst the analytical, FE and DIC strain/stress distributions along the bond-line is observed. This study introduces the analytical shear-lag model as an alternative to predict the stress state in thick-adhesive double-lap joints, with an acceptable level of accuracy and robustness. The program is available here.

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