Modelling the tensile fracture behaviour of CFRP scarf repairs

Campilho, R.D.S.G.; Moura, M.F.S.F. de; Pinto, A. M. G.; Morais, J.J.L.; Domingues, J. J. M. S.

doi:10.1016/j.compositesb.2008.10.008

Cited by 160 publications

(99 citation statements)

References 30 publications

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“…Maximum deviations of 0.3% were found relatively to the average value of Pm between the four mesh sizes (independent analysis for each adhesive). This behaviour was expected, since in CZM modelling an energetic criterion is used for damage propagation, (sx) was found for the joints with LO ¼ 80 mm (610.7 MPa for the joints with Araldite s 2015 and 393.9 MPa for the joints with Araldite s AV138), being much smaller in magnitude to the tensile strength of the employed composite, of E 2000 MPa [14]. Adding to this, a detailed stress analysis to the joints for the range of LO values used in this work was undertaken.…”

Section: Joint Strengthmentioning

confidence: 99%

“…For all of the three CZM shapes, initiation of damage was evaluated by the (for a¼ 0 a triangular law is attained). In this work, a ¼ 7 was following quadratic nominal stress criterion, previously tested for accuracy [14], and expressed as [39] chosen to provide a significant difference to the triangular shape, by a significantly faster degradation after t 0 is reached. For the trapezoidal law, the stress softening displacements in tension and origin, given by [39] decaying slope up to d f (e.g.…”

Section: Czm Implementation In the Fe Analysismentioning

confidence: 99%

“…Developed CZM include triangular [17], linear-parabolic [18], polynomial [19], exponential [20] and trapezoidal laws [21]. Thus, CZM can also be adapted to simulate ductile adhesive layers, whose behaviour can be approximated with trapezoidal laws [14]. Although it is always advised the use of the most suitable CZM shape and to perform accurate parameter estimations, few works showed acceptable predictions for small variations to the optimal CZM parameters and shapes [11,22].…”

Section: Introductionmentioning

confidence: 99%

“…The property identification technique consists on the separated calculation of each one of the cohesive law parameters by suitable tests, while in the inverse method the CZM parameters are estimated by iterative fitting the FE prediction with experimentally measured data (typically the load-displacement, P-d, curve) up to an accurate representation. Both of these approaches begin with the assumption of a CZM shape to simulate a specific material, which approximately replicates it in terms of post-elastic behaviour [14]. On the other hand, the direct method gives the precise shape of the CZM laws of a specific material or interface, since these are estimated from the experimental data of fracture tests such as the DCB or ENF [15].…”

Section: Introductionmentioning

confidence: 99%

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Modelling adhesive joints with cohesive zone models: effect of the cohesive law shape of the adhesive layer

Campilho

Banea

Neto

et al. 2013

International Journal of Adhesion and Adhesives

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492

193

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Adhesively-bonded joints are extensively used in several fields of engineering. Cohesive Zone Models (CZM) have been used for the strength prediction of adhesive joints, as an add-in to Finite Element (FE) analyses that allows simulation of damage growth, by consideration of energetic principles. A useful feature of CZM is that different shapes can be developed for the cohesive laws, depending on the nature of the material or interface to be simulated, allowing an accurate strength prediction. This work studies the influence of the CZM shape (triangular, exponential or trapezoidal) used to model a thin adhesive layer in single-lap adhesive joints, for an estimation of its influence on the strength prediction under different material conditions. By performing this study, guidelines are provided on the possibility to use a CZM shape that may not be the most suited for a particular adhesive, but that may be more straightforward to use/implement and have less convergence problems (e.g. triangular shaped CZM), thus attaining the solution faster. The overall results showed that joints bonded with ductile adhesives are highly influenced by the CZM shape, and that the trapezoidal shape fits best the experimental data. Moreover, the smaller is the overlap length (LO), the greater is the influence of the CZM shape. On the other hand, the influence of the CZM shape can be neglected whe n using brittle adhesives, without compromising too much the accuracy of the strength predictions.

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Section: Joint Strengthmentioning

confidence: 99%

Section: Czm Implementation In the Fe Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Modelling adhesive joints with cohesive zone models: effect of the cohesive law shape of the adhesive layer

Campilho

Banea

Neto

et al. 2013

International Journal of Adhesion and Adhesives

Self Cite

492

193

View full text Add to dashboard Cite

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“…CZM rely in the definition of the cohesive strength in tension and shear, t 0 n and t 0 s , respectively (relating to the end of the elastic regime and beginning of damage), and the fracture toughness in tension and shear, G c n and G c s respectively (accounting for the amount of allowable plasticization prior to failure). A few methods are available to estimate the cohesive parameters and the respective laws: the property identification and inverse methods consist on assuming a simplified shape (bilinear or trilinear) for the fracture laws and defining the respective parameters by standardized procedures, while the direct method estimates the precise law shape by computing it based on fracture characterization data [14]. This is accomplished by the differentiation of the strain energy release rate in tension (G n ) or shear (G s ) with respect to the relative opening (d n for tension or d s for shear).…”

Section: Introductionmentioning

confidence: 99%

Fracture toughness determination of adhesive and co-cured joints in natural fibre composites

Campilho

Moura

Gonçalves

et al. 2013

Composites Part B: Engineering

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a b s t r a c tAdhesive bonding has become more efficient in the last few decades due to the adhesives developments, granting higher strength and ductility. On the other hand, natural fibre composites have recently gained interest due to the low cost and density. It is therefore essential to predict the fracture behavior of joints between these materials, to assess the feasibility of joining or repairing with adhesives. In this work, the tensile fracture toughness (G c n ) of adhesive joints between natural fibre composites is studied, by bonding with a ductile adhesive and co-curing. Conventional methods to obtain G c n are used for the co-cured specimens, while for the adhesive within the bonded joint, the J-integral is considered. For the J-integral calculation, an optical measurement method is developed for the evaluation of the crack tip opening and adherends rotation at the crack tip during the test, supported by a Matlab sub-routine for the automated extraction of these quantities. As output of this work, an optical method that allows an easier and quicker extraction of the parameters to obtain G c n than the available methods is proposed (by the J-integral technique), and the fracture behaviour in tension of bonded and co-cured joints in jute-reinforced natural fibre composites is also provided for the subsequent strength prediction. Additionally, for the adhesively-bonded joints, the tensile cohesive law of the adhesive is derived by the direct method.

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