Enhanced Failure Load Bearing in Adhesively Bonded Strap Repairs: Numerical Analysis and Experimental Results
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TECHNICAL ARTICLE—PEER-REVIEWED
Enhanced Failure Load Bearing in Adhesively Bonded Strap Repairs: Numerical Analysis and Experimental Results Mohammad Ali Saeimi Sadigh
Submitted: 13 November 2017 / in revised form: 17 April 2018 / Published online: 23 January 2019 Ó ASM International 2019
Abstract Adhesively bonded repairs are frequently used to repair aluminum structures due to their attractive options compared to traditional methods such as welding or riveting. A new method of increasing the repair’s strength against uniaxial tensile loads is used in this study. For this purpose, standard single-strap (SS) and double-strap (DS) repairs were produced with aluminum patch. In the first step, an epoxy-based adhesive was employed to create SS and DS repairs using neat adhesive and 0.5 wt.% reduced graphene oxide (RGO)-reinforced adhesive. Afterward, samples of SS and DS joints with the reinforced adhesive were manufactured to study the effect of the added RGO. Uniaxial tensile tests were conducted and above 30% enhancement in the ultimate load was observed in the joints bonded with reinforced adhesive. The repaired joints were analyzed by finite element (FE) method using cohesive zone modeling technique to obtain failure loads. For this purpose, two sets of tests (a) double cantilever beam and (b) end notch flexure tests were implemented to estimate the cohesive zone model CZM parameters. Comparing the results obtained from experiments and the numerical simulations shows that FE models accurately predict the failure load in the reinforced and unreinforced repaired joints. Keywords Patch repair Adhesive Cohesive zone model RGO List of symbols B Specimen width M. A. Saeimi Sadigh (&) Department of Mechanical Engineering, Azarbaijan Shahid Madani University, Tabriz, Iran e-mail: [email protected]
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D I GIIC GIC p TI TII d di do,i t
Diagonal matrix Identity matrix Energies released (mode II) Energies released (mode I) Applied load Maximum normal nominal stress Maximum shear nominal stress Vector of relative displacement Current damage relative displacement in mode I Onset damage relative displacement in mode II Poisson’s ratio
Introduction Several events such as impact of a bird against aircraft or flying aircraft through hail storms cause damage to the surface of the aircraft. Depending on the velocity of impact or greatness of the hail, considerable damage may occur on the front face of the aircraft. Additionally other problems such as fatigue or corrosion create cracks on the aircraft’s surface which cause high stress concentration in the structural components. In addition, rivet holes are known as the most susceptible places for crack initiation in the aircraft skin. One of the commonly used methods for repairing the damages mentioned above is applying a patch over the crack. Path repair is accomplished by means of riveting an aluminum patch over the damaged area or applying adhesive patches on the damaged surface. In the last decades, applying adhesive patches have gained more popularity in c
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