A detailed experimental study of the effects of pre-bond contamination with a hydraulic fluid, thermal degradation, and poor curing on fracture toughness of composite-bonded joints

Τσερπές, Κωνσταντίνος; Markatos, Dionysios N.; Brune, Kai; Hoffmann, Michael M.; Rau, E.; Pantelakis, Spiros

doi:10.1080/01694243.2014.925387

Cited by 25 publications

(25 citation statements)

References 21 publications

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“…[3,4,5] As a consequence, fracture toughness values under opening mode (G IC ) significantly decrease, which is a direct result from the crack growing at the interface instead of inside the adhesive layer (cohesive failure-good adhesion quality). [6,7] The same studies also show that neither ultrasonic C-scan nor X-ray tomography are able to detect those defects prior to testing.…”

Section: Introductionmentioning

confidence: 80%

The use of acoustic emission and composite peel tests to detect weak adhesion in composite structures

Freitas

Zarouchas

Poulis

2018

The Journal of Adhesion

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Adhesive bonding is one of the most promising joining technologies for composite aircraft. However, to comply with current aircraft certification rules, current safety-critical bonded joints, in which at least one of the interfaces requires additional surface preparation, are always used in combination with redundant mechanical fasteners, such as rivets and bolts. This lack of trust in bonded structures is mostly linked to the fear of lack of adhesion or a "weak bond".The aim of this paper is to tackle this challenge by assessing the ability to use composite peel tests and acoustic emission (AE) technique to assess adhesion quality and distinguish a good bond quality from a "weak bond".Composite Bell Peel (CBP) tests and Double-CantileverBeam (DCB) tests were performed on contaminated and noncontaminated CFRP bonded specimens. The results show that peel strength drops significantly at the location of the contaminated interface that has led to weak adhesion, as a result from adhesive failure. The AE signals obtained during DCB tests show different features for cracks growing at the interface ("weak bonds") and inside the adhesive layer (cohesive failure). In addition to this, scattering of the AE signals were observed in the contaminated specimens with "weak bonds". ARTICLE HISTORY

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Section: Introductionmentioning

confidence: 80%

The use of acoustic emission and composite peel tests to detect weak adhesion in composite structures

Freitas

Zarouchas

Poulis

2018

The Journal of Adhesion

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“…According to the literature, the pre-bond thermal treatment results in decrease of GIC value by 10 and 13 % for treatment at 190 and 200°C, respectively [1]. In the case of treatment at 210°C the increase by 9% was observed [1]. In the case of improper curing of the adhesive, it was shown that the lowered temperature have great impact on the bond performance.…”

Section: Introductionmentioning

confidence: 99%

“…The pre-bond contamination or modification have an influence on the fracture toughness of the CFRP bonded joints. According to the literature, the pre-bond thermal treatment results in decrease of GIC value by 10 and 13 % for treatment at 190 and 200°C, respectively [1]. In the case of treatment at 210°C the increase by 9% was observed [1].…”

Section: Introductionmentioning

confidence: 99%

Study of CFRP adhesive bonds influenced by factors encountered during aircraft operations

Malinowski¹,

Wandowski²,

Ostachowicz³

et al. 2018

Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2018

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Abstract.Composite materials are commonly used in many branches of industry. One of the effective meth ods to join CFRP parts is to use adhesives. There is a search of effective methods for quality assurance of bonded parts. There is a need for pre-and post-bond inspection to ensure proper bonding and verify its quality. Research reported here focuses on post-bond inspection of bonded CFRP parts. In this paper we report investigations of samples that were modified in order to simulate the conditions that can be encountered during the bonding repair processes. The modifications were made before adhesive bonding, and their effect on the quality of the bond is studied. The first case was the thermal treatment. It was made by exposure of samples to elevated temperatures. This case accounts for parts that may be exposed to external heat source or lightening impac t. Second of the investigated cases was deicing fluid contamination prepared by dip-coating of clean CFRP plates. When cleaning the aircraft for a repair this fluid can be transported to bonding areas and weaken the joint. The third type of modification was faulty curing of the adhesive. It was prepared by local pre-curing of the adhesive. Pre-curing causes irregularities in the curing of the adhesive joint. Apart from single modifications, also mixed cases were studied, as well as scarf bonding. The samples were studied in non-destructive approach. It was shown that for some of the cases the detection is possible.*pmalinowski@imp.gda.pl; phone +48 58 5225 174; fax +48 58 341 61 44; www.imp.gda.pl/en/o4/z1/

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“…However, there is evidence of adhesion strength improvement for the case of the low temperature. Thermal degradation results in the thermo-oxidation of the resin [16,24]. Depending on the temperature level applied, this may either lead to the improvement of the resin performance due to the presence of carboxyl bonds or cause the development of an oxidized layer which hinders the adhesion at the surface of the CFRP substrate [16].…”

Section: Hoffmann Et Almentioning

confidence: 99%

“…the fuselage parts stroked by lightning [24] causing local overheating and damage of the matrix or the wing parts which are close to the engines. Besides the loss in the mechanical properties of the structural parts, thermal degradation of the CFRP parts might also affect bonding in a repair.…”

Section: Pre-bond Contamination Of Cfrpsmentioning

confidence: 99%

Determination of adhesion strength of pre-bond contaminated composite-to-metal bonded joints by centrifuge tests

Hoffmann

Τσερπές

Moutsompegka

et al. 2018

Composites Part B: Engineering

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A B S T R A C TIn the present work, the effect of pre-bond contamination scenarios related to production and repair processes on the adhesion strength of composite-to-metal joints is investigated by means of the novel centrifuge testing technology. The composite substrates have been subjected to contamination with release agent, moisture, fingerprint, thermal degradation and de-icing fluid before being bonded on the metallic stamp. Different contamination levels have been considered for each scenario. The standard deviation of adhesion strength values differs for each sample category and in some cases, is relatively high. The experimental results show a considerable decrease of adhesion strength for all contamination scenarios. The evaluation of the adhesion strength values is assisted by the characterization of the failure modes. In most cases, the transition between the failure modes explains the variation of adhesion strength. By taking into advantage the simplicity of the experimental process, numerous tests have been conducted within a very short time. Based on the practicality of the experimental process and the validity of the findings, it can be concluded that the centrifuge testing technology can be potentially used as a reliable testing method for the characterization of bonded joints.

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A detailed experimental study of the effects of pre-bond contamination with a hydraulic fluid, thermal degradation, and poor curing on fracture toughness of composite-bonded joints

Cited by 25 publications

References 21 publications

The use of acoustic emission and composite peel tests to detect weak adhesion in composite structures

The use of acoustic emission and composite peel tests to detect weak adhesion in composite structures

Study of CFRP adhesive bonds influenced by factors encountered during aircraft operations

Determination of adhesion strength of pre-bond contaminated composite-to-metal bonded joints by centrifuge tests

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