Paris law relations for an epoxy-based adhesive

Due to their inherent advantages, the use of adhesive joints is widely increasing in advanced industrial sectors such as automotive and aircraft structures, where the lightweight components play a significant role in the efficiency of the products. These structural adhesively bonded connections mostly experience cyclic stress conditions during their service life. One of the most critical fatigue loading conditions for adhesive joints is the tensile cyclic loading. To design against tensile fatigue conditions recently a cohesive zone modelling (CZM) technique combined with a degradation approach was proposed in the literature. However, to apply this degradation method on cohesive elements, the total fatigue life of the joints should be known before the analysis. The aim of the current work is to improve this degradation approach to calculate the fatigue life automatically. To achieve this, a combination of Paris law and degradation model were considered in a numerical procedure. Using the Paris law and the experimental results obtained out of the fatigue crack propagation tests of DCB (double cantilever beam) specimens, the tensile fatigue life of each integration point (IP) during the analysis is estimated automatically. The model was validated and calibrated by experimental data.

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“…The joints were already tested at 60% of their static strength. 29 The mechanical and fatigue properties of the adhesive are shown in Table 3.…”

Section: Resultsmentioning

confidence: 99%

“…28 An investigation on different Paris law relations can be found in. 29 As the normalized strain energy was considered by Costa et al. 20 to develop the fatigue degradation method, the same Paris law relations is also used in the current study (equation (9)).…”

Section: Numerical Toolmentioning

confidence: 99%

Tensile fatigue life prediction of adhesively bonded structures based on CZM technique and a modified degradation approach

Akhavan‐Safar

Monteiro

Carbas

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part G:

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“…34,35 Chan and Wang 36 then proposed a normalized strain energy to solve this issue. Rocha et al 37 recently investigated the effect of different fatigue parameters on the Paris' law curves where the R ratio or load level are different. As the initial degradation approach is based on the normalized strain energy, 25 the modified method proposed in this study is also using the same fatigue parameter for the shear fatigue crack growth analysis (equation ( 13)).…”

Section: Modified Degradation Methodsmentioning

confidence: 99%

A modified degradation technique for fatigue life assessment of adhesive materials subjected to cyclic shear loads

Akhavan‐Safar

Monteiro

Carbas

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part C:

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Understanding the fatigue response of adhesive joints under cyclic shear stress is important to avoid fatigue failure of the bonded structures. Recently, a cohesive zone modelling (CZM) technique was developed where the cohesive properties of the elements were degraded by a proposed empirical relation. However, based on this degradation approach, the fatigue life of the joints should be known before running the analysis. The aim of the current study is to improve the numerical method in which the fatigue life of the joints will be automatically estimated during the analysis. To achieve this, the concepts of fracture mechanics are considered by using the Paris’ law combined with the degradation model. A user material subroutine is developed to conduct the numerical calculations based on the concepts of CZM. End notched flexure (ENF) tests were carried out to evaluate the numerical data. Based on the results, it was found that the modified approach, in which the total fatigue life is obtained automatically, can be employed for fatigue life assessment of adhesive joints subjected to cyclic shear stresses.

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“…The relation between the FCG rate and the fracture parameter was first developed for metals as a function of the stress intensity factor

[ 27 ], the linear range of which is called the Paris’ law region. For composites and adhesives, the strain energy release rate

is more commonly used than

, but much discussion still remains in the expression for

[ 28 , 29 ].…”

Section: Introductionmentioning

confidence: 99%

Effect of Bond-Line Thickness on Fatigue Crack Growth of Structural Acrylic Adhesive Joints

Sekiguchi

Sato

2021

Materials

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With an increasing demand for adhesives, the durability of joints has become highly important. The fatigue resistance of adhesives has been investigated mainly for epoxies, but in recent years many other resins have been adopted for structural adhesives. Therefore, understanding the fatigue characteristics of these resins is also important. In this study, the cyclic fatigue behavior of a two-part acrylic-based adhesive used for structural bonding was investigated using a fracture-mechanics approach. Fatigue tests for mode I loading were conducted under displacement control using double cantilever beam specimens with varying bond-line thicknesses. When the fatigue crack growth rate per cycle, da/dN, reached 10−5 mm/cycle, the fatigue toughness reduced to 1/10 of the critical fracture energy. In addition, significant changes in the characteristics of fatigue crack growth were observed varying the bond-line thickness and loading conditions. However, the predominance of the adhesive thickness on the fatigue crack growth resistance was confirmed regardless of the initial loading conditions. The thicker the adhesive bond line, the greater the fatigue toughness.

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Paris law relations for an epoxy-based adhesive

Cited by 25 publications

References 21 publications

Tensile fatigue life prediction of adhesively bonded structures based on CZM technique and a modified degradation approach

Tensile fatigue life prediction of adhesively bonded structures based on CZM technique and a modified degradation approach

A modified degradation technique for fatigue life assessment of adhesive materials subjected to cyclic shear loads

Effect of Bond-Line Thickness on Fatigue Crack Growth of Structural Acrylic Adhesive Joints

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