On the design methodology of scarf repairs to composite laminates

Wang, Chun H.; Gunnion, Andrew J.

doi:10.1016/j.compscitech.2007.05.045

Cited by 146 publications

(83 citation statements)

References 11 publications

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“…Studies on composite scarf joints or repairs were employed by many researchers [29][30][31][32][33]. However, a scarf joint in a composite structure is more complex because, unlike lap or stepped-lap joints, the stiffness of the bonded surface varies along the bondline.…”

Section: Effect Of Joint Configurationmentioning

confidence: 99%

Adhesively bonded joints in composite materials: An overview

Banea

Silva

2009

Proceedings of the Institution of Mechanical Engineers, Part L:

469

330

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A review of the investigations that have been made on adhesively bonded joints of fibre-reinforced plastic (FRP) composite structures (single skin and sandwich construction) is presented. The effects of surface preparation, joint configuration, adhesive properties, and environmental factors on the joint behaviour are described briefly for adhesively bonded FRP composite structures. The analytical and numerical methods of stress analysis required before failure prediction are discussed. The numerical approaches cover both linear and non-linear models. Several methods that have been used to predict failure in bonded joints are described. There is no general agreement about the method that should be used to predict failure since the failure strength and modes are different according to the various bonding methods and parameters, but progressive damage models are quite promising since important aspects of the joint behaviour can be modelled by using this approach. However, a lack of reliable failure criteria still exists, limiting in this way a more widespread application of adhesively bonded joints in principal load-bearing structural applications. An accurate strength prediction of the adhesively bonded joints is essential to decrease the amount of expensive testing at the design stage.

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Section: Effect Of Joint Configurationmentioning

confidence: 99%

Adhesively bonded joints in composite materials: An overview

Banea

Silva

2009

Proceedings of the Institution of Mechanical Engineers, Part L:

469

330

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show abstract

“…The outcome of the optimization of stresses is a higher strength for the same bond area than strap repairs [24], which renders scarf repairs more suited to critical applications [25]. The substantial or full strength recovery achieved by this method, provided that the repair is correctly designed, usually makes scarf repairs as permanent [26][27][28][29]. Conversely to strap techniques, scarf repairs are also flush with the damaged structure, which is an important advantage since aerodynamic disturbance is prevented and stealth characteristics (if relevant) are not compromised.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, they require a large repair area, since relatively small angles are necessary to restore the strength of components [27,29,31]. The execution of this repair initiates by machining a tapered cavity to remove the damaged material and to provide the repair geometry.…”

Section: Introductionmentioning

confidence: 99%

Numerical evaluation of three-dimensional scarf repairs in carbon-epoxy structures

Pinto¹,

Campilho

Moura

et al. 2010

International Journal of Adhesion and Adhesives

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The widespread employment of carbon-epoxy laminates in high responsibility and severely loaded applications introduces an issue regarding their handling after damage. Repair of these structures should be evaluated, instead of their disposal, for cost saving and ecological purposes. Under this perspective, the availability of efficient repair methods is essential to restore the strength of the structure. The development and validation of accurate predictive tools for the repairs behaviour are also extremely important, allowing the reduction of costs and time associated to extensive test programmes. Comparing with strap repairs, scarf repairs have the advantages of a higher efficiency and the absence of aerodynamic disturbance. This work reports on a numerical study of the tensile behaviour of three-dimensional scarf repairs in carbon-epoxy structures, using a ductile adhesive (Araldite s 2015). The finite elements analysis was performed in ABAQUS s and Cohesive Zone Modelling was used for the simulation of damage onset and growth in the adhesive layer. Trapezoidal cohesive laws in each pure mode were used to account for the ductility of the specific adhesive mentioned. A parametric study was performed on the repair width and scarf angle. The use of over-laminating plies covering the repaired region at the outer or both repair surfaces was also tested as an attempt to increase the repairs efficiency. The obtained results allowed the proposal of design principles for repairing composite structures.

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“…The non-uniformity of the stresses along the scarf bondline shown in Figure 3 would result in severe load-carrying penalties even for ductile adhesives, because the average shear stress in a composite repair remains below the adhesive's yield strength [4]. Therefore, it is possible to achieve higher joint strength by optimising the scarf shape so that the stress concentration is minimised.…”

Section: Formulation Of the Optimisation Problemmentioning

confidence: 99%

“…This simplification significantly reduced the modelling and computational effort required. Although this simplification is known to influence the local stress state within the adhesive bondline, the influence is well documented and understood [1][2][3][4], making it relatively easy to transfer any design implications to the more complex scenario of a composite laminate. The boundary conditions, loads and material are such that the model symmetry can be exploited to further reduce the computational effort.…”

Section: Computational Assessmentmentioning

confidence: 99%

Optimum shapes for minimising bond stress in scarf repairs

Wang

Gunnion²

2008

Australian Journal of Mechanical Engineering

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Bonded scarf repairs are used in composite structures when high strength recovery is needed or when there is a requirement for a flush surface to satisfy aerodynamic or stealth requirements. However, scarf repairs are complex to design and require the removal of significant parent structure, particularly for thick skins. In this investigation, analytical and numerical approaches have been developed to investigate whether an optimum repair shape for a known biaxial load can be determined. The results clearly demonstrate that the strength of a repaired panel can be improved by optimising both the initial damage cut-out shape and the scarf angle distribution.

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On the design methodology of scarf repairs to composite laminates

Cited by 146 publications

References 11 publications

Adhesively bonded joints in composite materials: An overview

Adhesively bonded joints in composite materials: An overview

Numerical evaluation of three-dimensional scarf repairs in carbon-epoxy structures

Optimum shapes for minimising bond stress in scarf repairs

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