Strength improvement of adhesively-bonded scarf repairs in aluminium structures with external reinforcements

Moreira, R.D.F.; Campilho, R.D.S.G.

doi:10.1016/j.engstruct.2015.07.001

Cited by 51 publications

(21 citation statements)

References 45 publications

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“…However, smaller values of α have the advantage of presenting an increasingly larger bond length and area, which cancels the peak stresses effect and results in much higher P m values. The P m evolution with α is typically exponential, which agrees with previous results [6]. In fact, a significant increase in strength was found for α smaller than 20°, while for bigger α the differences are minimal.…”

Section: Discussion On the Joint Strengthsupporting

confidence: 91%

“…more time-consuming to fabricate (i.e., they require milling operations). This type of joint, when loaded, has the ability to keep the axis of loading aligned with the joint [6]. Besides that, it allows a practically constant stress distribution when manufactured with an optimized value of α.…”

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confidence: 99%

“…The assembly of a mixed-mode CZM from this information, including criteria for damage initiation and growth prediction, enables to design bonded structures under arbitrary loadings. This method was applied in the work of Moreira and Campilho [6], to assess the strength improvement of bonded scarf repairs in aluminium structures with distinct external reinforcements, using the adhesive Araldite ® 2015 (Araldite ® from Huntsman, Basel, Switzerland). Fairly accurate numerical approximations were attained, but generally with slightly smaller P m values compared to the experiments.…”

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confidence: 99%

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Application a direct/cohesive zone method for the evaluation of scarf adhesive joints

et al. 2018

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IntroductionThe use of adhesive bonds in the aerospace, aeronautical and automotive industries, among others, has assumed a high preponderance to the detriment of conventional joining methods such as riveting, bolting, brazing and welding. In fact, adhesive bonds offer several advantages such as the reduction of stress concentrations, good response to fatigue stresses, ability to bond dissimilar materials and lightness of structures. However, they also present some limitations, namely the difficulty of disassembly, high cure times (in some cases) and limited temperature and humidity conditions [1]. The strength and behaviour of adhesive bonds depends on several factors, namely the type of adhesive used, the material of the adherends, the joint configuration and dimensional factors, such as the overlap length (L O ) and the adhesive and adherends' thickness (t A and t P , respectively). There are several types of joint geometries, although the most common are single-lap, double-lap and scarf [2][3][4][5]. Scarf joints are modified butt joints that are AbstractWith the increasing use of structures with adhesive bonds at the industrial level, several authors in the last decades have been conducting studies concerning the behaviour and strength of adhesive joints. Between the available strength prediction methods, cohesive zone models, which have shown good results, are particularly relevant. This work consists of a validation of cohesive laws in traction and shear, estimated by the application of the direct method, in the strength prediction of joints under a mixedmode loading. In this context, scarf joints with different scarf angles (α) and adhesives of different ductility were tested. Pure-mode cohesive laws served as the basis for the creation of simplified triangular, trapezoidal and exponential laws for all adhesives. Their validation was accomplished by comparing the numerical maximum load (P m ) predictions with the experimental results. An analysis of peel (σ) and shear (τ) stresses in the adhesive layer was also performed to understand the influence of stresses on P m . The use of the direct method allowed obtaining very precise P m predictions. For the geometric and material conditions considered, this study has led to the conclusion that no significant P m errors are incurred by the choice of a less appropriate law or by uncoupling the loading modes.

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Section: Discussion On the Joint Strengthsupporting

confidence: 91%

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Application a direct/cohesive zone method for the evaluation of scarf adhesive joints

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“…This material presents several important features, which were relevant during the material selection, such as the good mechanical properties and the wide field of structural applications in the laminated form. This alloy was characterized in a previous study [25], on bulk specimens, from which the results depicted in Tab. 2 were obtained.…”

Section: Joint Materials (Fracture Tests and Lap Joints)mentioning

confidence: 99%

“…t n and t s are the current tensile and shear tractions, respectively, and  n and  s the corresponding strains. A suitable approximation for thin adhesive layers is provided with Knn=E, Kss=Gxy and Kns=0 [25]. Damage initiation can be specified by different criteria.…”

Section: Mixed-mode Triangular Modelmentioning

confidence: 99%

Validation of fracture envelopes of structural adhesives for mixed-mode strength prediction of bonded joints

Campilho

Ribeiro²,

Rocha³

et al. 2019

Frattura Ed Integrità Strutturale

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In the design of adhesive structures, it is extremely important to accurately predict their strength and fracture properties (critical strain energy release rate in tension, GIC, and shear, GIIC). In most cases, the loads occur in mixed-mode (tension plus shear). Thus, it is of great importance the perception of fracture in these conditions, namely of the strain energy release rates in tension, G I , and shear, G II , relative to different crack propagation criteria or fracture envelopes. This comparison allows to determine the most suitable energetic propagation criterion to be used in cohesive zone models (CZM). The main objective of this work is to verify, by CZM, which is the power parameter () that best suits the energetic crack propagation criterion for CZM modelling, using single-lap joints (SLJ) and double-lap joints (DLJ) with aluminium adherends and bonded with three different adhesives. With this purpose, numerical simulations of the SLJ and DLJ are carried out, and the maximum load (Pm) is compared with experiments. For the Araldite ® AV138 and Araldite ® 2015, the energetic criterion resulting from the experimental work provided matching numerical results and, thus, the fracture envelopes were validated. The Sikaforce ® 7752 results were slightly offset due to CZM law shape issues.

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Mixed-mode fracture analysis of composite bonded joints considering adhesives of different ductility

Santos

Campilho

2017

Int J Fract

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Strength improvement of adhesively-bonded scarf repairs in aluminium structures with external reinforcements

Cited by 51 publications

References 45 publications

Application a direct/cohesive zone method for the evaluation of scarf adhesive joints

Application a direct/cohesive zone method for the evaluation of scarf adhesive joints

Validation of fracture envelopes of structural adhesives for mixed-mode strength prediction of bonded joints

Mixed-mode fracture analysis of composite bonded joints considering adhesives of different ductility

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