Assessment of Microscale Test Methods of Peeling and Splitting along Surface of Thin-Film/Substrates
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Assessment of Microscale Test Methods of Peeling and Splitting along Surface of Thin-Film/Substrates Y. Wei LNM, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080, P.R. China ABSTRACT Peel test methods are assessed through being applied to a peeling analysis of the ductile film/ceramic substrate system. Through computing the fracture work of the system using the either beam bend model (BB model) or the general plane analysis model (GPA model), surprisingly, a big difference between both model results is found. Although the BB model can capture the plastic dissipation phenomenon for the ductile film case as the GPA model can, it is much sensitive to the choice of the peeling criterion parameters, and it overestimates the plastic bending effect unable to capture crack tip constraint plasticity. In view of the difficulty of measuring interfacial toughness using peel test method when film is the ductile material, a new test method, split test, is recommended and analyzed using the GPA model. The prediction is applied to a wedge-loaded experiment for Al-alloy double-cantilever beam in literature. INTRODUCTION The peel test method has been widely used for the mechanical characterization of adhesion phenomena in various applications involving adhesive joining and thin film technology in industries as diverse as the micro-packaging and micro-electronic industries and the automotive industry. It has received considerable attention in the past several decades, and continues to be the subject of intense scrutiny in a wide range of research areas [1,2]. Most mechanical applications are used to measure the interfacial toughness for such a film/substrate system. However, when adherent, film or substrate, is a ductile material, the measurement of the interfacial fracture toughness using the peel test method becomes much difficult even impossible due to plastic dissipation. Therefore, it is important to separate the plastic dissipation from peel test work. For this purpose, several analytical models have been presented. Two representative models are the beam bend model [3] (BB model) and the more recently proposed general plane analysis model [4] (GPA model). Before the GPA model was presented, the BB model had undergone the much attention [5-8]. By the BB model, the thin film is assumed to undergo the elastic-plastic bending deformation, and plastic dissipation comes only from the plastic bending of film, while the plastic dissipation from crack tip constraint (crack tip "singularity" effect) can not be caught. On the GPA model [4], the plastic dissipation includes two contribution sources of both the plastic bending of film and the crack tip constraint. In the present research, the peel test analytical models mentioned above will be assessed through adopting them to a peeling problem of a ductile film/ceramic substrate system. The steady-state fracture work is computed using the either BB model or the GPA model. Through checking and comparing the results of both models, three fundamental objectives hope to be at
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