Failure analysis of thin metal foils

AIP Conference Proceedings

2018

Abstract. The evolution of the fracture processes occurring in thin metal foils can be evidenced by tensile tests performed on samples of non-standard dimensions. The load versus displacement record of these experiments does not return directly the local stress-strain relationship and the fracture characteristics of the investigated material. In fact, the overall response of thin foils is sensitive to local imperfections, size and geometric effects. Simulation models of the performed tests can support the interpretation of the experimental results, provided that the most significant physical phenomena are captured. The present contribution focuses on the role of modelling details on the numerical output that can be obtained in this context.

Section: Problem Formulation and Modelling Assumptionsmentioning

confidence: 99%

“…These disturbances can be detected by three-dimensional digital correlation techniques [14,15] and potentially reproduced by finite element analysis. However, numerical models based on slightly different assumptions can lead to rather different conclusions.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of non-standard tensile tests of thin metal foils

Bolzon

AIP Conference Proceedings

2018

“…The results showed that peak stress and the corresponding strain increase with the adhesion level, and a higher adhesion level leads to higher peak stress in the laminate. In [ 14 ], the failure behavior of thin freestanding Al foil under a uniaxial tensile test was evaluated, and the authors could reproduce a failure mechanism of Al foil similar to the experimental test behavior using a numerical method. The results of this study are crucial for a better understanding of the mechanical behavior of Al foil in Al/polymer laminate.…”

Section: Introductionmentioning

confidence: 99%

The Role of Interfacial Adhesion on the Mechanical Behavior of Thin Metal/Polymer Laminate with Surface Roughness

Mohammadi

2022

Polymers

Metal/polymer laminate has versatile applications in industry due to the essential roles of its constituents in controlling its mechanical behavior. Therefore, efforts to enhance a laminate’s performance should target its mechanical behavior. One of the most influencing features of the mechanical behavior of this type of thin laminate is the interface layer properties. This study concentrates on the mechanical response of thin aluminum (Al) foil deposited on a polymer substrate by calibrating its interfacial layer properties based on available uniaxial tensile tests performed on thin Al/polymer laminate. Then, taking into account the calibrated parameters for the interface layer, which leads to mimicking the real conditions of the laminate, one type of imperfection is introduced as a wavy roughness on the surface of each layer with different amplitudes to investigate its influence on the overall mechanical behavior of the laminate and its failure mode. The results highlighted that the existence of the roughness on the surface of the polymer layer reduces the maximum engineering stress of the laminate more severely compared to other conditions. As the roughness amplitude increases, the maximum stress reduces a lot. The distribution of equivalent plastic strains represents the appearance of the shear bands in the Al layer and an almost uniform distribution for the polymer layer. In the case of existing roughness on each layer, a higher amount of plastic strain accumulation occurs in the middle of the polymer layer and top corners of the thin Al layer. Due to the significant effect of interfacial layer properties to improve the maximum strength of the laminate and its final elongation, a parametric study is performed, taking into account different interfacial properties. The results indicate that laminate behavior with weaker separation properties in the interface layer is mostly unaffected by adopting higher tractions, and no change happens in the case of high separation considering weak tractions.

“…An initially notched sheet under tensile load reveals some compression zones around the crack area due to compression stresses. The existence of these compression stresses in sheets with small thickness-to-width/length ratio leads to local buckling around the crack and the formation of wrinkles on the surface of the sheets [1][2][3][4][5][6][7]. Due to the wide application of thin sheets in different fields, from civil engineering [8][9][10] to mechanical [11][12][13] and aerospace engineering [14,15], numerous researchers have studied the buckling behavior of thin sheets with initial cracks.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Buckling and Post-Buckling Behavior of a Central Notched Thin Aluminum Foil with Nonlinearity in Consideration

Ståhle

Islam

et al. 2020

Metals

In thin notched sheets under tensile loading, wrinkling appears on the sheet surface, specifically around the cracked area. This is due to local buckling and compression stresses near the crack surfaces. This study aims to numerically study the buckling behavior of a thin sheet with a central crack under tension. A numerical model of a notched sheet under tensile loading is developed using the finite element method, which considers both material and geometrical nonlinearity. To overcome the convergence problem caused by the small thickness-to-length/width ratio and to stimulate the buckling, an imperfection is defined as a small perturbation in the numerical model. Both elastic and elasto-plastic behavior are applied, and the influence of them is studied on the critical buckling stress and the post-buckling behavior of the notched sheet. Numerical results for both elastic and elasto-plastic behavior reflect that very small perturbations need more energy for the activation of buckling mode, and a higher buckling mode is predominant. The influences of different parameters, including Poisson’s ratio, yield limit, crack length-to-sheet-width ratio, and the sheet aspect ratio are also evaluated with a focus on the critical buckling stress and the buckling mode shape. With increase in Poisson’s ratio. First, the critical buckling stress reduces and then remains constant. A higher yield limit results in increases in the critical buckling stress, and no change in the buckling mode shape while adopting various crack length-to-sheet-width ratios, and the sheet aspect ratio changes the buckling mode shape.