• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.334-339
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• 2020

In this study, the adhesion properties between aluminum and composite materials, composite materials, and composite materials were compared according to the physical surface treatment to improve mechanical bonding at the bonding surface when considering carbon fiber and glass fiber-reinforced composite materials. Bonded specimens were classified into the type of base material and the surface treatment method of the bonding surface. Sandpaper, sandblasting, and plasma were applied as physical surface treatment methods. The bonded specimen was prepared as a single lap joint test specimen. An experiment to measure the lap shear strength was conducted, and the results were compared. The experimental results confirmed that the mechanical abrasion and sandblasting treatment improved the lap shear strength approximately 4 to 5 fold compared to the general specimen without physical surface treatment. In plasma treatment, the experiment was conducted by defining the respective plasma output and treatment time as follows: 150 W and 5 minutes, 150 W and 10 minutes, and 300 W and 3 minutes. Moreover, the lap shear strength results were similar to the previous mechanical surface treatments. On the other hand, the effect on the adhesion properties was small, depending on the plasma treatment conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.2
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• pp.119-128
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• 2010

The hygrothermal effect on the strength of composite single-lap bonded joints were investigated. The specimens were manufactured in four different manufacturing methods and tested in three different environmental conditions. An interesting result is that the strengths of the joints in the elevated temperature and wet (ETW) conditions were found to be 11 ~ 23% higher than those in the room temperature and dry (RTD) environment. In contrast, the strengths of the joints in the cold temperature and dry (CTD) condition decrease by 8 ~ 21% compared to those in the RTD environment except for cobonded joint. The difference in the strength by testing environments is mainly attributed to the change of the material properties of adhesive by temperature and moisture.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.3
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• pp.157-164
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• 2003

The pulse-echo method is one of the most widely used ultrasonic techniques for application of nondestructive evaluation. Particularly, quantitative nondestructive evaluation of defects has been considered more important to assure the reliability and the safety of structure. Frequency energy in adhesive joints is based on the ultrasonic wave analysis. The attenuation coefficient upon wave amplitude and the frequency energy that is expressed in the term of wave pressure amplitude were utilized for the primary wave experiment. By means of a control experiment, it was confirmed that the variation of the frequency energy in adhesive joints depends on transition by stress variation. In this paper, the ultrasonic characteristics were measured for single lap joint and Double Cantilever Beam specimen with different fracture modes that was subjected to stress. Consequently, the data that was obtained from the adhesive specimen was analytically compared to the fracture mechanics parameter

• Composites Research
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• v.16 no.5
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• pp.45-53
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• 2003

The experimental and numerical investigations on the failure characteristics of the secondary bonded composite single-lap joints were performed. The initiations and growths of cracks were observed using CCD camera and acoustic emission sensor during the tension tests of the joint specimens. The structural behaviors of the specimens were predicted by the geometric nonlinear two-dimensional finite element analysis. The three types of observed initial cracks were included in each finite element models and the strain energy release rates of each specimen models were calculated by VCCT(Virtual Crack Closure Technique) technique. The tension tests showed that the initial cracks occurred in the 60∼90% of final failure loads and the major failure modes of the specimens were adhesive failure and the delamination between the 1st and 2nd ply of laminate. The specimens with the thicker bondline had earlier crack initiation loads but higher crack propagation resistance and eventually better loading capability. The delaminations were mostly observed in the thicker bondline specimens. The mode I values of calculated strain energy release rates were higher than the mode II values in the all specimen models considering the three types of initial cracks. The mode I and total strain energy release rates were calculated as higher values in the order of initial crack in the edge interface, comer interface and delamination between the plies of laminate.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.7 s.262
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• pp.808-815
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• 2007

The optical performance of the mirror fur satellite camera is highly dependent on the adhesive properties between the mirror and its support. Therefore, in order to design a mirror with high optical performance, the mechanical properties of adhesives should be well defined. In this research, the mechanical properties of three kinds of space adhesives are studied. In case of the materials which show nearly incompressible behavior such as space adhesives, it is important to measure shear modulus which governs deviatoric stress components. Also the experiment should be performed in circumstances similar to real manufacturing process of mirror, because extra factors such as size effects, the adhesion effects of primer and reactions between adhesive and primer affect the properties of adhesive regions. In this research shear moduli of the adhesives are determined by using a single lap adhesively bonded joint. For the shear tests, several temperatures have been selected from $-20^{\circ}C$ to $55^{\circ}C$ which is operating temperature range of the adhesive. In the case of linear behavior materials, shear moduli are calculated through a linear curve fitting. Shear stress-strain relation is obtained by using an exponential curve fitting for material which shows non-linear behavior. The shear modulus of each adhesive is expressed as a function of temperature. Characteristics and adaptability of the adhesives are discussed regarding their temperature sensitivity.

• Journal of the Korean Society for Railway
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• v.13 no.6
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• pp.546-551
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• 2010

In this paper, the strain distribution of the bond layer has been compared with the experimental data and analyzed according to the different mesh refinements and element types. The mesh density was changed along the longitudinal direction of adherend, the longitudinal direction of overlapped region, the vertical direction of adherend, the vertical direction of adhesive and the width direction of the joint. In addition, the effect of the different types of element was evaluated using soild, shell and plane strain element. The geometric nonlinear analysis was performed to consider the large deformation of the joint. From the numerical result, at least 2 elements were needed to achieve a reliable result as the solid element used. In case of shell element, the peel strain at x/c=1 showed 22.8% error compared with the experiment but the shear strain showed a good agreement with the experiment within 1.67% error.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.11
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• pp.1115-1122
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• 2010

The main objective of this study is to experimentally investigate the effect of adhesive thickness and environmental conditions on the failure and strength of sandwich-to-laminate bonded joints. Three different adhesive thicknesses (t=0.2, 2 and 4 mm) and two different environmental conditions were considered. Environmental conditions include the RTD(room temperature and dry condition) and ETW(elevated temperature and wet condition). Test results show as the adhesive thickness increases from 0.2 mm to 2 and 4 mm, the joint strength decreases 16 and 30%, respectively. Regarding the effect of environmental conditions, except for one case, the joint strength in the ETW conditions turned out to be 12% higher than those in the RTD conditions. In the joints with adhesive thickness of 0.2 mm, remarkable difference from RTD condition was not found.

• Journal of Adhesion and Interface
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• v.5 no.2
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• pp.22-36
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• 2004

Several in-situ testing methods of adhesively bonded joints under static short-time tensile loading are critically analyzed in terms of experimental procedure and data evaluation. Due to its rather homogeneous stress state across the glue line, the tensile-shear test with thick single-lap specimens, according to ISO 11003-2, has become the most important test process for the determination of realistic materials parameters. This basic method, which was improved in both, the experimental part by stepped adherends and easily attachable extensometers and the evaluation procedure by numeric substrate deformation correction and test simulation based on the finite element method (FEM), is therefore demonstrated by application to several kinds of adhesives and metallic adherends. Multi-axial load decreases the strength of a joint. This effect, which is illustrated by an experimental comparison, impedes the derivation of realistic mechanical characteristics from measured force-displacement curves. It is shown by numeric modeling that tensile-shear tests with thin plate substrates according to ISO 4587, which are widely used for quick industrial quality assurance, reveal an inhomogeneous stress state, especially because of relatively large adherend deformation. Complete experimental determination of the elastic properties of bonded joints requires independent measurement of at least two characteristics. As the thick-adherend tensile-shear test directly yields the shear modulus, the tensile butt-joint test according to ISO 6922 represents the most obvious complement of the test programme. Thus, validity of analytical correction formulae proposed in literature for the derivation of realistic materials characteristics is verified by numeric simulation. Moreover, the influence of the substrate deformation is examined and a FEM correction method introduced.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.149-153
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• 2000

Substituting composite structures for conventional metallic structures has many advantages because of higher specific stiffness and specific strength of composite materials. In this work, one-piece propeller shafts composed of carbonfepoxy and glass/epoxy composites were designed and manufactured for a rear wheel drive automobile satisfying three design specifications, such as static torque transmission capability, torsional buckling and the fundamental natural bending frequency. Single lap adhesively bonded joint was employed to join the composite shaft and the aluminum yoke. For the optimal adhesive joining of the composite propeller shaft to the aluminum yoke, the torque transmission capability of the adhesively bonded composite shaft was calculated with respect to bonding length and yoke thickness by finite element method and compared with the experimental result. Then an optimal design method was proposed based on the failure model which incorporated the nonlinear mechanical behavior of aluminum yoke and epoxy adhesive. From the experiments and FEM analyses, it was found that the static torque transmission capability of composite propeller shaft was maximum at the critical yoke thickness, and it saturated beyond the critical length. Also, it was found that the one-piece composite propeller shaft had 40% weight saving effect compared with a two-piece steel propeller shaft.

• Steel and Composite Structures
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• v.26 no.3
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• pp.265-272
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• 2018

A detailed study was carried out on the tensile properties of the single-lap joint of a steel panel bolted/bonded to a composite laminate with a flanging. Finite element model (FEM) was established to predict the strength and to analyze the damage propagation of the hybrid joints by ABAQUS/Standard, which especially adopted cohesive elements to simulate the interface between the laminate and adhesive. The strength and failure mode predicted by FEM were in good agreement with the experimental results. In addition, three influence factors including adhesive thickness, bolt preload and bolt-hole clearance were studied. The results show that the three parameters have effect on the first drop load of the load-displacement curve, but the effect of bolt-hole clearance is the largest. The bolt-hole clearance should be avoided for hybrid joints.