Strength of CFRP joints reinforced with adhesive layers

Morgado, Margarida; Carbas, R.J.C.; Santos, D.; Silva, Lucas F. M. da

doi:10.1016/j.ijadhadh.2019.102475

Cited by 22 publications

(15 citation statements)

References 15 publications

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“…However, for the tough adhesive, failure loads for all adherends are within a range of 6%, showing that the mechanical properties of the adhesive Figure 7. Cohesive zone modelling scheme used on toughened materials (a) Toughening by polymer (ALR) 19 (b) toughening by metal (FML). 36 Figure 8.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…3,19,36 For the adherends, quadratic 4-node plain strain quadrilateral elements referenced on the software library as CPE4R for the were used, while for the adhesive quadradic 4-node cohesive elements for the adhesive layer, referenced as COH2D4. 3,19,36 The adherends were divided in 21 layers with different stiffness properties, according to the distributional exponential laws evaluated as presented in Figure 4. It should be highlighted that the model evaluated on the present work considers that the adherends suffer no plastic deformation, being the damage only located on the adhesive layer.…”

Section: Numerical Proceduresmentioning

confidence: 99%

“…Concerning of the numerical analysis, the CZM is stablished as a very accurate method, widely used to assess the strength of bonded joints, 3,15,19,36,37 and have been used in several works, once it was able to predict the failure load in several scenarios as impact, fatigue, mixed-adhesive and graded adhesive joints. 3,15,19,36,37 The use of CZM emulates the failure process on the bond line, through the application of elements with fracture toughness, strength and elasticity properties, which allow the model to simulate the crack nucleation, growing and propagation on the adhesive, when the failure criteria is reached in an element. 3,38 The ratio between the stress and displacement previously, during and after the crack initiation is ruled by a traction separation law.…”

Section: Numerical Proceduresmentioning

confidence: 99%

“…The numerical model used was validated with experimental results in previous works by the authors, regarding of adhesive joints with modified adherends by surface toughening by polymers and metals. 18,19,36 The surface toughening can be seen as rough version of functionally graded adherends, while in graded adherends the properties change gradually, in modified adherends by surface toughening, the enhance on the joint resistance is obtained by the modification of one or more layers of the adherend and often with a modified interface. 22 This results in an adherend and a numerical model with several layers with different properties, as presented in Figure 7.…”

Section: Validation Of the Modelmentioning

confidence: 99%

“…Modified adherends using additional layers of polymers and metals were presented in literature as being capable to also enhance joint strength. 18,19 Moreover, reinforcements in the transverse direction as z-pinning and stitching also presented excellent capabilities to increase the strength of adhesive joints with composite substrates. [20][21][22] Furthermore, gradual changes on the adherends properties and construction, in order to obtain a directional stiffness variation, were also proposed in the literature.…”

Section: Introductionmentioning

confidence: 99%

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Numerical modelling of functionally graded adherends

Reis

Carbas

Marques

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part C:

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The development of lighter structures and materials has been one of the main research concerns of the transportation industry during the last decade, driven by the necessity to decrease fuel consumption and emissions. Therefore, the use of several different new lightweight materials, such as special metal alloys, reinforced polymers and new advanced composite materials has been explored, leading to optimized structures which combine these novel materials. To manufacture these multi-material structures, adhesive bonding is one of best joining techniques available, as fasteners add weight to the structure and require holes to be drilled and welding is not easily applicable to reinforced plastics, composites and some high strength metal alloys. However, adhesive bonding also presents some limitations that need to be considered, such as the appearance of singularities and the resultant stress concentration at the edges of the bond line, which result in a reduction of the joint strength. In order to mitigate this effect, several techniques have been proposed, being the use of functionally graded adherends one of them. Functionally graded adherends consist in an adherend where the mechanical properties gradually change throughout the material, usually in the thickness or length direction. The present work introduces the concept of a layered functionally graded adherend, varying the flexibility of each layer through the thickness direction. Different ratios of stiffness variation, combined with different adhesive properties, were numerically evaluated for single lap joints, comparing the stress distribution of the adhesive layer and the resultant joint strength, using cohesive zone modelling. Moreover, an optimization process of typical graded material properties, where different distribution laws that consider material weight and strength are considered, is presented.

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Section: Numerical Resultsmentioning

confidence: 99%