On the influence of the adhesive and the adherend ductility on mode I fracture characterization of thick adhesively-bonded joints

Mohamed Saleh, Michal K. Budzik, Milad Saeedifar, Dimitrios Zarouchas, Sofia Teixeira de Freitas
January 2022
Cite DOI URL

Abstract

Thicker bondlines along with manufacturing-tolerant and fracture-resistant adhesives are trends visible across different industries, especially maritime. In this work, two contrasting adhesives: an elastic-brittle epoxy-based, and a nonlinear-ductile methyl methacrylate (MMA) are characterized and compared via tensile, compact tension (CT) and double cantilever beam (DCB) testing, for steel-to-steel adherends. Significant differences are captured between the two bonding materials in terms of the energy required for crack growth: in the MMA “ductile” adhesive is ∼4 and 10 times more than for the epoxy “relatively brittle” adhesive for CT and DCB testing, respectively. While epoxy bondlines fail due to a symmetric in-plane crack, the MMA bondlines experience multiple cracking originating from high deformations and Poisson’s effects. Moreover, in the case of MMA adhesive, the DCB testing led to plastic deformation of steel adherends. The existing evaluation protocols are adopted for data reduction and the effect of plastic dissipation is theoretically addressed. Despite adherend plasticity, it is concluded that the crack growth is driven by the elastic energy release, and thus, after small correction taking into account initial adherend plasticity, the existing simple models can still be used. This study highlights the potential use of ductile adhesive instead of the commonly used brittle ones to significantly improve the adhesively bonded joints in maritime applications in which thick bondlines, manufacturing-tolerant and fracture-resistance characteristics are required.

Type
Journal article
Publication
International Journal of Adhesion and Adhesives
Adhesive Testing Fracture Testing Methyl Methacrylate (MMA) Plastic Deformation Thick Bondlines
Mohamed Saleh
Postdoc Researcher

My research interests in fracture mechanisms of bi-material bonded joints with thick bondlines.

Sofia Teixeira de Freitas
Sofia Teixeira de Freitas
Principal Investigator

Sofia Teixeira de Freitas researches the structural integrity of bonded and layered materials to enable durable, sustainable structures. She is also an accredited group facilitator, committed to building academic environments grounded in cooperation and inclusion—key to overcoming technological limits and addressing the challenges of a truly sustainable society.