Computationally Informed Adhesion Measurement Using the Blister Test

Date
2023
Authors
Dahal, Drishya
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Abstract

The adhesion of thin films is crucial in several engineering fields, ranging from corrosion protection through coatings to structurally bonding dissimilar materials in the aerospace and automotive sectors. The effectiveness of these films highly depends on their adhesion to rigid substrates. Therefore, investigating the adhesion mechanics between thin films and rigid substrates is an essential research area with significant implications for commercial sectors and scientific understanding. However, quantifying the adhesion strength is a complex task. While many different adhesion tests are available, the Blister Test (BT) has been identified as a superior method for adhesion quantification. In this test, the substrate-coating interface is pressurized and allowed to debond, enabling the quantification of the energies required to initiate and delaminate the film.

The first chapter of this thesis presents a novel method to characterize the mechanical mix-mode adhesion characteristics between thin films and rigid substrates using the BT. This method couples the full triaxial displacement field obtained though Digital Image Correlation (DIC) with Finite Element Method (FEM) simulations, eliminating the need to assume blister shapes or make other mechanistic assumptions. The proposed technique allows the characterization of the full traction-separation law governing the adhering layer-substrate interface.

In the second chapter, effects of surface treatment on adhesion is investigated for aluminum alloys adhered to Polyvinyl Butyral (PVB) and a Betamate 4601 epoxy adhesive. This adhesion assessments are performed using the BT, cross-hatch test, and filiform corrosion experiments. Further evaluations included adhesion measurement after exposure to relative humidity cycle and salt solution immersions.

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Keywords
Blister Test, cohesive element (CZM), Digital Image Correlation (DIC), inverse finite element, PPR cohesive element
Citation
Department
Mechanical Engineering