• Journal of Welding and Joining
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• 제30권6호
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• pp.62-67
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• 2012

In this study, the bonding strengths of adhesively bonded joints are experimentally investigated. A series of lap-shear tests are conducted using single lap type adhesive joints. In order to analyse the joint fabrication factors that affected the bonding strength, the parametric tests are conducted with various thickness of adhesive, surface roughness and fillet of adhesive. In addition, for the comparative study with the welded joint, lap-shear tests using specimens with 2 welded sides and 4 welded sides are also carried out. The quantitative results of the strength analysis are summarized, and some proposals are made on setting up testing standards for adhesively bonded joints.

• Composites Research
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• 제35권5호
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• pp.322-327
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• 2022

복합재 체결부는 뛰어난 물성과 가벼운 구조의 수요로 널리 사용되고 있다. 하지만 두께 방향의 취약한 물성으로 인해 체결부 파손이 쉽게 발생한다. 이를 극복하기 위하여 체결부 끝단의 집중되는 응력을 완화시켜주는 Z-피닝, 스티칭 등 다양한 공법들이 적용되고 있다. Z-피닝 공법은 프리프레그의 두께 방향으로 금속 핀이나 카본 핀을 적용하여 보강하는 공법이고, 스티칭 공법은 프리폼에 상부 및 하부 섬유를 교차시켜 두께방향으로 기계적 강도를 향상시키는 방법이다. I-fiber 스티칭 공법은 Z-pinning 공법과 Stitching 공법을 보완한 유망한 공법이다. 본 논문에서는 I-fiber 스티칭 공법으로 보강된 Single-lap joint 시편을 오토클레이브 진공백 성형법으로 제작하여, 모재의 두께와 스티칭 각도에 따른 인장강도 및 피로강도 특성을 평가하여, I-fiber 보강 복합재 체결부 구조물의 보강효과를 검증하였다. 실험결과, 복합재 체결부의 두께가 얇을수록 I-fiber 보강효과가 더 높게 나타났으며 I-fiber로 보강된 복합재 체결부는 파손강도에서 약 52%, 피로강도에서 약 118% 우수한 특성을 나타냄을 확인하였다.

• 한국항공우주학회지
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• 제41권8호
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• pp.613-618
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• 2013

본 논문에서는 복합재 구조물의 제작 현장에서 쉽게 적용할 수 있는 장점을 갖는, 저자에 의하여 'Z-피닝 패치'로 명명된 새로운 Z-피닝 기술에 대하여 소개하였다. 시제작된 'Z-피닝 패치'를 사용하여 Z-핀이 박힌 복합재 단일-겹침 전단 접합시편을 성공적으로 제작하였고, 접합강도의 향상을 점검하기 위하여 시험을 수행하였다. Z-핀의 재질은 스테인레스 강이며, 복합재료와의 접합력을 향상시키기 위하여 Z-핀의 표면은 요철 형상으로 가공하였으며, 화학적으로 부식시켰다.

• 오토저널
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• 제13권5호
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• pp.42-50
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• 1991

According as the members and inner and outer plates of the automobile body structure have been thinned their thickness and have become high strength, each part of the body structure has been put more severe stress condition. Therefore, it has been increasingly required to improve the fatigue strength of the spot welded structures. As one of the improving methods for such problem, the author had previously proposed the method of alleviating stress concentration at nugget edge of the spot weld part and improving its fatigue strength [1]. But, because fatigue strength of the spot welded lap joint is influenced by its geometrical and mechanical factors, welding condition and etc., there needs a quantitative and systematic estimation method of them. In this report, by considering nugget edge of the spot weld part of the spot welded lap joint subjected to tensile load to the ligament crack, fatigue strength of various spot welded lap joints was estimated with the stress intensity factor (S.I.F.) K which is fracture mechanical parameter. It is known that evaluation of fatigue strength of the spot welded lap joint by the stress intensity factor (S.I.F.) K is more effective than the maximum stress $(\sigma_{ymax}$) at edge of the spot weld part on the center line of width of the plate.

• 대한기계학회논문집A
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• 제24권8호
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• pp.2022-2031
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• 2000

Since the surface roughness of adherends affects much the strength of adhesivelybonded joints, the effect of surface roughness on the fatigue life of adhesively bonded tubular single lap joints was investigated analytically and experimentally by fatigue torsion test. The stiffness of the interfacial layer between adherends and adhesive was modeled as a normal statistical distribution function of surface roughness of adherends. From the investigation, it was found that the optimum surface roughness of adherends for the fatigue strength of tubular single lap joints was dependent on bondthickness and applied load.

• 한국해양공학회지
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• 제24권1호
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• pp.172-177
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• 2010

This study presents an explicit dynamic analysis of an adhesively bonded single-lap joint under an impact load. The finite element software, ANSYS LS-DYNA, was used for the analysis and Von Mises stresses were obtained from the analysis. To model the adherents, solid elements were used and a rigid body was assumed for impactor modeling. Three impact heights (1 m, 5 m, and 10 m) were applied to consider different impact conditions and infinite boundary conditions were applied to the end-area of each adherent to save computational time in the analysis. In addition to investigating the stresses in the normal state, we also investigated the stresses in a damaged state (elasticity deterioration), simulated by a change in Young's modulus for 36 of the 3600 elements in the upper layer of the adhesive. The results showed that the location of damage is critical to the stress state of each layer (upper, middle, and lower).

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.238-243
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• 2007

This paper is designed to estimate the adhesion strength of coating layer on galvannealed steel sheet using lap shear test. The single lap shear test is the most commonly used standard test for determining the strength of medium-strength and high strength bonds. The bond strength of bonded single lap joints on subjecting the substrates to loads is determined by lap shear forces in the direction of the bonded joint. In this study, specimen for adhesion strength test was made to attach coated sheet to cold rolled sheet and were heated in temperature of 180 for 20minutes. After test, detached parts of coatings on coated sheet were observed using SEM and EDX to identify substrate and complete detachment. The tested results showed that adhesive strength of coating is unrelated to anisotropy of sheet and is difficult to be extracted using conventional theory because of fine cracks of coating layers which were created during annealing process.

• 대한기계학회논문집
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• 제18권4호
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• pp.835-845
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• 1994

In this paper, the effects of the adhesive thickness and adherend roughness on the static and fatigue strengths of the adhesively bonded circular single lap joints has been investigated by an experimental method. The stacking sequence effect of the composite adherend on the static and fatigue strength and the fracture patterns of the adhesive failure were also observed. Since the circular single lap joint fails catastrophically beyond the static strength of fatigue limit, the tubular polygonal adhesively bonded joints such as triangular, tetragonal, pentagonal, hexagonal as well as elliptical joints were manufactured in order to give partial mechanical characteristics to the adhesively bonded tubular joints. These joints were tested both in static and fatigue modes. From the experimental investigations, it was found that the fatigue strength of the circular adhesively bonded joints was much dependent on the arithmetical average surface roughness of the adherends and the polygonal adhesively bonded joints had better fatigue strength characteristics than the circular adhesively bonded joints.

• Composites Research
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• 제17권6호
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• pp.14-21
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• 2004

본 연구에서는 몇 가지 접합 방법에 따라 일방향 복합재료 단일 겹치기 접합 조인트의 파손 과정, 모드 및 강도를 실험적으로 평가하였다 접합 방법으로는 접착제 없는 동시성형, 접착제를 사용한 동시성형 및 이차 접합의 세 가지를 고려하였다 또한 이차 접합 조인트에서 몇 가지 파라미터의 영향도 살펴보았다. 접착제 없는 동시성형 시편은 가장 우수한 조인트 강도를 나타내었다. 이차접합 조인트에서는 접착제 층의 점진적인 파손이 발생하였다. 접착제의 재료 및 접합 강도가 상대적으로 강한 필름 접착제의 동시성형 조인트는 갑작스런 층간분리 파손이 발생하였으며 이차 접합 조인트보다 더 낮은 파손 강도를 나타내었다. 이차 집합 조인트에서 층간분리 파손이 발생하지 않은 것은 접착제 층에서의 균열 진전 및 점진적 파손이 층간분리 파손을 방지한 것으로 보인다. 따라서 복합재료 접합 조인트의 파손 강도는 접착제의 재료 강도 또는 접착 성능과 항상 비례하지 않으며 이것은 복합재료가 층간 분리 파손에 약하기 때문이다.

• Journal of Welding and Joining
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• 제32권5호
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• pp.44-49
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• 2014

The effect of weldbond hybrid joining process on the mechanical behavior of single lap and L-tensile joints was investigated for the newly developed 1.2GPa grade ultra high strength TRIP(transformation induced plasticity) steel. In the case of single lap shear behavior, the weldbond joint of 1.2GPa TRIP steel showed lower maximum tensile load and elongation than that of the adhesive bonding only. It was considered to be due to the reduction of real adhesion area, which was caused by the degradation of adhesive near the spot weld, and the brittle fracture behavior of the spot weld joint. In the case of L-tensile behavior, however, the maximum tensile load of the weldbond joint of 1.2GPa TRIP steel was dramatically increased and the fracture mode was change to the base metal fracture which is desirable for the spot weld joint. These synergic effect of the weldbond hybrid joining process in 1.2GPa TRIP steel was considered to be due to the stress dissipation around the spot weld joint by the presence of adhesive which resulted in the change of crack propagation path.