• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.5
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• pp.53-64
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• 2012

Deep and narrow welds can be produced by laser welding at high welding speeds with a narrow heat-affected zone (HAZ) and little distortion of the workpiece. This study aims to evaluate the usefulness of laser welding at automobile component manufacture. Microstructure observation, hardness test, tensile test and fatigue life test are performed by using the fiber laser welded SPFC590 steel sheets which is used widely in the manufacture of automotive seat frame. Three kinds of specimens are only a SPFC590 steel plate, quasi-butt joint plate and lap joint plate by laser welding. The following results that will be helpful to understand the static strength, fatigue crack initiation and growth mechanism were obtained. (1) The tensile strength of quasi butt joint specimens nearly equal to base metal specimens, but lap joint specimens fractured in shear area of weld metal. (2) The fatigue strength of quasi-butt joint specimen was approximately 8 percent lower than that of the base metal specimens. Furthermore, the lap joint specimens were less than 86 percent of the base metal specimens. (3) The lap joint fatigue specimens fractured at shear area in high level stress amplitude, while fractured at normal area in low level stress amplitude. From these results, the applicability of the laser welding to the automobile component is discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.4
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• pp.905-915
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• 1998

Static tensile tests using adhesive-bonded single-lap joints of aluminum alloy were conducted to investigate the effect of geometric factor, overlap length, adherend thickness, adhesive thickness and material composition of adherend/adhesive on the strength of adhesive joint. The average applied shear stress at joint fracture decreased with increasing lap length. However increasing the adherend thickness resulted in a higher joint strength. Higher yield strength of adherend and lower elastic modulus of adhesive is advantageous to the adhesive joint. Newly proposed modified joint factor could be well evaluated the influence of lap length, adherend thickness and adhesive thickness on the bond strength for adhesive joints.

• Journal of the Korean institute of surface engineering
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• v.34 no.3
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• pp.225-230
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• 2001

In this study, the effect of surface treatment of CFRP (Carbon Fiber Reinforced Composites) on the shear strength of CFRP/metal composites was investigated. The surface of 14 plied unidirectional (0-dog ) CFRP was treated by an $Ar^{/}$ + ion beam under an oxygen environment. Shear strength tests were performed using SLS (Single Lap Shear) specimens based on the ASTM D906-94a procedure. The shear strength of the surface-treated CFRP/metal composites was compared with that of the untreated CFRP/metal composites. The results showed that the shear strength of surface-treated CFRP/metal composites was 36% greater than that of untreated CFRP/metal composites.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.75-78
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• 2000

This study investigates the effect of surface treatment on the shear strength between aluminum panel and composite plate. The aluminum panel was surface-treated by DC Plasma and the composite Plate was surface-treated by ion beam. Lap shear test and T-peel test were performed to determine the shear strength and T-peel strength. Results showed that the shear strength of surface-treated case was 2.5 times higher than that of untreated case. The T-peel strength of treated case was more than 5 times higher than that of untreated case. SEM examination showed that the strength increase of surface-treated case was due to the more spread of epoxy to the panel.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.5 s.248
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• pp.481-487
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• 2006

Spot-welding is a widely used manufacturing method for thin-sheet components, especially in mass-production industries such as the car industry. Automobiles are often constructed by multi-lap spot welding to secure the passenger from the accident, where optimisation of the welding conditions is a major economic consideration. This research is conducted to investigate weldability characteristics with various welding conditions on the 4-lap spot welded joint of structural steel sheets in automobile. The relationship between the tensile-shear strength and the indentation depth has been investigated to propose the optimum welding conditions. The welding current and the welding time have a greater effect on the welding characteristics than the electrode force. It was found that the electrode force has a relatively close relationship with the expulsion occurrence. The design curves for optimum welding are proposed for the 4-lap spot welded joint.

• Journal of Adhesion and Interface
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• v.25 no.1
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• pp.162-168
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• 2024

The effect of maleinized polybutadiene (MPB) on the mechanical properties of epoxy resins including adhesion strength, elongation and impact peel resistance was investigated in this study, in which MPB is an anhydride-functionalized polybutadiene prepolymer. Different molecular weights (3.1K and 5.6K) of MPB were added to diglycidyl ether bisphenol-A (DEGBA), an epoxy resin, to increase its impact peel strength and elongation. At various loading percent (5, 10, 15, 20 and 25 wt%) of MPB in the epoxy resin, significant improvements of mechanical properties were observed. According to the comparative analysis results, the modified epoxy system with 15 wt% (3.1K) MPB exhibited the highest lap shear strength, about 40% higher than that of neat epoxy. The tensile strength and elongation steadily and simultaneously increased as the loading percent of MPB increased. The impact peel strengths at low (-40℃) and room (23℃) temperatures were substantially improved by MPB incorporation into epoxy resins. Reactive and flexible MPB prepolymer seems to construct strong nano-structured networks with rigid epoxy backbones without sacrificing the tensile and adhesion strengths while increasing impact resistance/toughness and elongation properties. For higher impact peel while maintaining adhesion and tensile strengths, approximately 10-15 wt% MPB loading in epoxy resin was suggested. Consequently, incorporation of functionalized MPB prepolymer into epoxy system is an easy and efficient way for improving some crucial mechanical properties of epoxy resins.

• Composites Research
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• v.35 no.2
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• pp.86-92
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• 2022

This study was conducted to determine the effect of molecular formation of adhesive on interface characterization of thermoplastic composites. Carbonfiber/polyetherketoneketone (CF/PEKK) thermoplastic composites were fusion bonded and PEEK, PEI adhesive bonded using a high-temperature oven welding process. In addition, lap shear strength test and fracture surface analysis using a digital optical microscope and a scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR) were performed. As a result, the adhesive bonding method improved adhesion strength with interphase having increased molecular formation of ether groups, ketone groups, and imide groups which mainly constitutes the CF/PEKK and adhesives. Furthermore, it was found that the use of PEEK containing more ether groups and ketone groups forms a more strongly bonded interphase and enhances the adhesive force of the CF/PEKK composites.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.12
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• pp.967-974
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• 2013

Recently the authors had proposed the z-pinning patch concept to simply manufacture z-pinned composite structures at industrial production site and manufactured composite single-lap shear joint specimens using the concept. Through static tensile test on the specimens they had obtained 54~68% improvement of the joint strength. As a sequential study of it, in this study, fatigue test has performed to measure an improvement of joint strength under cyclic loading. The z-pin's material is stainless steel and its surface was specially machined into zagged shapes and chemically corroded to increase the connection force with composite materials. Approximately 98~125% improvement of the joint strength under cyclic loading was obtained.

• Proceedings of the KWS Conference
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• 2000.10a
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• pp.94-97
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• 2000

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.6
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• pp.728-735
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• 2003

This paper shows the possibility of performing Lap joint using the friction stir welding with $2mm^t$ aluminum alloy plate and the determination of tool-dimensions for FSW in milling machine. This research also is reported on obtaining the tensile-shear strength, 91.3 (MPa) and the energy absorption, 26.3 (J) for Lap jointed specimen. The optimal tool-dimensions and method for Lap joint using FSW is as follows; each diameter of shoulder and pin is $9\phi(mm) and 3\phi(mm)$, the length of pin is 3.6(mm), Pressing the shoulder of tool into original base metal is not reasonable.