Single-lap Adhesive Joints Research Articles

Experimental Study of Effect of Adhesives on Strength of Composites Adhesive Joints

Tension tests on T700/EXOPY unidirectional laminates and 3-D and six-directional braided composites single-lap adhesive joints with different adhesive types under uniaxial tensile loading are performed in the presented paper. Failure modes, strengths and load-displacement curves of two kinds of different adhesive joints are compared and analyzed. According to the experimental results, it is found that the strength of the joints of the smaller adhesive shear strength is less, in contrast, the strength of the joints of the bigger adhesive shear strength is greater, Failure shear strength average is grown 27% relatively. And the starting position of the crack is appeared at the overlap ends, and the whole joint is failed with propagation of the crack.

Experimental and FEM studies on mechanical properties of single-lap adhesive joint with dissimilar adherends subjected to impact tensile loadings

The rupture initiation position, the stress wave propagations and interface stress distributions of the single-lap adhesive joint with dissimilar adherends under impact tensile loadings are analyzed via experiments combined with FEM calculations taking account of the strain rate dependency property of the adhesive. It is obtained that rupture initiates at the interface of the adherend with higher Young's modulus (steel side in this study) in the joint under impact tensile loadings, which shows the opposite characteristic in the same type of joint under static loadings. A fairly good agreement is observed between the experimental measured and FEM calculated results. In addition, it is also found that the strength of the joint with dissimilar adherends is smaller than that of the joint with similar adherends when the joint is subjected to the impact tensile loadings owing to the different extent of the wave impedance mismatch which depends on the material properties. Finally, the design guideline for the single-lap adhesive joint is summarized and provided.

Modelling adhesive joints with cohesive zone models: effect of the cohesive law shape of the adhesive layer

Adhesively-bonded joints are extensively used in several fields of engineering. Cohesive Zone Models (CZM) have been used for the strength prediction of adhesive joints, as an add-in to Finite Element (FE) analyses that allows simulation of damage growth, by consideration of energetic principles. A useful feature of CZM is that different shapes can be developed for the cohesive laws, depending on the nature of the material or interface to be simulated, allowing an accurate strength prediction. This work studies the influence of the CZM shape (triangular, exponential or trapezoidal) used to model a thin adhesive layer in single-lap adhesive joints, for an estimation of its influence on the strength prediction under different material conditions. By performing this study, guidelines are provided on the possibility to use a CZM shape that may not be the most suited for a particular adhesive, but that may be more straightforward to use/implement and have less convergence problems (e.g. triangular shaped CZM), thus attaining the solution faster. The overall results showed that joints bonded with ductile adhesives are highly influenced by the CZM shape, and that the trapezoidal shape fits best the experimental data. Moreover, the smaller is the overlap length (LO), the greater is the influence of the CZM shape. On the other hand, the influence of the CZM shape can be neglected when using brittle adhesives, without compromising too much the accuracy of the strength predictions.

Thermal behavior of DGEBA (Diglycidyl Ether of Bisphenol A) adhesives and its influence on the strength of joints

Adhesives, especially epoxies, are widely used as joints, repairs and corrosion protection in the petroleum onshore and offshore industry. Performance temperature is a key factor for such material. Mainly they are designed by the thermal properties but when they are in real service operation the behavior changes drastically. In this work, three different epoxy adhesives used in the offshore industry are characterized by DSC, DMA and TGA methods. The main objective is to verify if thermo mechanical tests on adhesives produces enough information to use in temperature service situation instead of test single lap joints (SLJ) at different temperatures. From the tests results it can be seen that adhesive SLJ should be tested in order to proper service design.

静的曲げモーメントを受ける被着体が竹板である単純重ね合わせ接着継手の応力と強度

木質材資源としてあまり有効に活用されていないタケを板材に加工し，接合方法の開発として単純重ね合わせ接着継手を作った。静的曲げモーメント作用させ継手の応力を有限要素法で計算した。継手表面のひずみに関する実験を行い実験結果と有限要素法による計算結果はかなりよく一致した。接着剤層界面端部の応力値が大きくなることがわかった。応力成分は繊維方向の引張応力と繊維直角方向（法線方向）の引張応力が同じ程度の大きさとなりせん断応力は小さくなることが分かった。この位置から繊維直角方向（法線方向）への被着体の破壊も予想された。強度実験を行い，破壊は被着体と接着剤層の界面端部のはく離から始まることが観察された。破面より被着体のはく離も観察された。接着剤層界面における繊維直角方向引張応力の応力特異場の強さから強度予測を行い強度実験結果と比較したところ推定値は実験値とかなりよく一致した。

Characterization of Aluminium Single-Lap Joints for High Temperature Applications

In this study, an experimental investigation into the shear strength behaviour of aluminium alloy single-lap adhesive joints was carried out in order to understand the effect of temperature on the strength of adhesively bonding joints. Single lap joints (SLJs) were fabricated and tested at RT and high temperatures (100°C, 125°C, 150°C, 175°C and 200°C). Results showed that the failure loads of the single-lap joint test specimens vary with temperature and this needs to be considered in any design procedure. It is shown that, although the tensile stress decreased with temperature, the lap-shear strength of the adhesive increased with increasing of temperature up to the glass transition of the adhesive (Tg) and decreased for tests above the Tg.

Research on the static strength performance of adhesive single lap joints subjected to extreme temperature environment for automotive industry

Adhesive bonding technique is widely studied and adopted in automotive industry in recent years, which leads to satisfactory joint mechanical properties and lightweight effects. In this study, the static mechanical performance of adhesively bonded joints after different temperature exposures was investigated through joint quasi-static shear-strength test. A response surface method using MATLAB programming was utilised to analyse the influences of exposure temperature and adhesive mechanical attributes on joint static strength. Visual inspection and scanning electron microscopy were later performed on the fracture surfaces to explain the failure mechanisms. Test results showed that long-term temperature exposure caused degradation in joint strength and failure displacement. It was found through response surface curve that comparing to higher temperature exposure, lower temperature causes greater and faster environmental degradation. Different types of fracture surfaces in the overlap zone were also detected through comparing adhesive joints under different environmental treatments.

Hygrothermal ageing of adhesive joints with nanoreinforced adhesives and different surface treatments of carbon fibre/epoxy substrates

The effect of water absorption on the strength of single lap adhesive joints subjected to accelerated hygrothermal ageing (55°C, 95% relative humidity, 800h) was analysed. Two different variables were studied: the surface treatment of the carbon fibre/epoxy laminates (peel ply, grit blasting and atmospheric pressure plasma) and the addition of carbon nanofillers (0.5wt% nanofibres and 0.25wt% nanotubes) to the epoxy adhesive. The joint strength and the failure mode of the joints were investigated. Furthermore, the amount of water absorbed by the adhesive was determined.Adhesive joints with peel ply-treated laminates exhibit an increase in their strength, which is attributed to a relaxation of stresses in the adhesive/laminate interface; with grit blasting, this property remains almost constant. Plasma treatment provides the worst ageing behaviour because this treatment results in a surface with a higher surface free energy, which is more susceptible to environmental attack. The nanoreinforcement of the adhesive has a beneficial effect: it decreases the amount of absorbed water.

Effect of temperature on the shear strength of aluminium single lap bonded joints for high temperature applications

An experimental and numerical investigation into the shear strength behaviour of adhesive single lap joints (SLJs) was carried out in order to understand the effect of temperature on the joint strength. The adherend material used for the experimental tests was an aluminium alloy in the form of thin sheets, and the adhesive used was a high-strength high temperature epoxy. Tensile tests as a function of temperature were performed and numerical predictions based on the use of a bilinear cohesive damage model were obtained. It is shown that at temperatures below Tg, the lap shear strength of SLJs increased, while at temperatures above Tg, a drastic drop in the lap shear strength was observed. Comparison between the experimental and numerical maximum loads representing the strength of the joints shows a reasonably good agreement.

Mechanical Behavior of Single-Lap Adhesive Joints with Reinforced Pins

An approach to increasing the loading ability of adhesive joints by adding reinforced pins is presented. Following procedures are taken for making adhesive joints with reinforced pins: At first, holes are drilled at the overlap region of adherends, and then one hole is filled with a metal pin and adhesive. At the same time, adhesive is also applied on the surfaces of the overlap of adherends. After cured, the metal pin and the adhesive in one hole form an adhesive-metal reinforced pin. In this study, strengths of single-lap adhesive joints with the reinforced pins were measured experimentally. It is found that to well-bonded joints, (1) the strength of single-lap adhesive joints with adhesive-metal pins are obviously greater than those without adhesive-metal pins; (2) the strength of single-lap adhesive joints with adhesive-metal pins is highest when the pins are located at the positions of 5mm from the two ends of the overlap segment, the strength of single-lap adhesive joints with adhesive-metal pins is lowest when the pins are located at the middle of the overlap segment, about 10mm from the two ends of the overlap segment.

Failure Analysis of Laminates Single-Lap Adhesive Joints under Uniaxial Tensile Loading

Tension tests on three different types of T700/EXOPY unidirectional laminates single-lap adhesive joints under uniaxial tensile loading were performed and effect of adherend thickness and spew fillets on strength of single-lap adhesive joints were analyzed in this paper. According to the experimental results, it is found that joint strength was not linear with the adherend thickness and much affected by spew fillets in overlap ends. At the same time, finite element simulations are carried out to analyze the peel/shear stress fields along joint interfaces and the intermediate layer of adhesive. The simulation results show that it is the main factor to leading to joint failure that the maximum peel/shear stress is occurred at overlap area edges and peel/shear stress of joints with spew fillet at the overlap area edges is less than that of joints with no spew fillet. Good agreements between the present simulations and the experimental results are found.

Effect of Parameters on Strength of Composites Single-Lap Adhesive Joints

Based on popular and maturate application of the finite element analysis method, a numerical study is presented for effect of parameters, that are composed of lap length, adhesive thickness and ply styles of adherend, on maximum peel/shear stress of T700/EXOPY composite single-lap adhesive joints in this paper. Finite element simulations are carried out to analyze the peel/shear stress fields along the interfaces between the adhesive and the adherends. The simulation results show that the joint maximum peel/shear stress decreases with increasing the lap length, and peel stress of the joint of adherends of ply style [0/90/±45/0]S is much less, and the maximum shear stress in the interfaces between the adhesive layer and the adherends do not dcreases all the times with increasing the adhesive thickness. Good agreements between the present simulations and the experimental results are found.

0712 静的曲げモーメントを受ける被着体が竹板である単純重ね合わせ接着継手の強度と強度推定(GS07-6 材料力学・計算力学,オーガナイズドセッション 3:「熱・流体の可視化と計測」)

0712 静的曲げモーメントを受ける被着体が竹板である単純重ね合わせ接着継手の強度と強度推定(GS07-6 材料力学・計算力学,オーガナイズドセッション 3:「熱・流体の可視化と計測」)

1809 引張荷重を受ける擬似等方積層CFRP単純重ね合せ接着継手の応力解析と強度(G04-2 複合材とサンドイッチ材,G04 材料力学部門)

Recently, carbon fiber reinforced plastic (CFRP) material has been used in structural element of transport vehicles. Besides, adhesive bonding is known as better method for joining the CFRP structures The purpose of our work was to examine the characteristics of strength for CFRP composite structures. We modeled single-lap adhesive joints composed of quasi-isotropic CFRP laminates having various lay-up pattern subjected to static tensile load to carry out finite element method analysis, and compared the analysis results of stress distribution at adhesive layer. In addition, failure load of various adhesive joint specimens were measured. As a result, it was found that the stress distributions on adhesive layer and failure load for joints were affected by each lay-up patterns of CFRP adherends.

Vibration Analysis of Single Lap Adhesive Joint with Non-Uniform Adhesive Thickness: Experimental and Analytical Investigation

This paper deals with the analytical and experimental vibration analysis of the single lap adhesive joint with non-uniform adhesive thickness . In the theoretical part, an analytical modal is described and a motion equation is built. A joint consists of two different adherends are bonded over a certain length by a viscoelastic material, epoxy resin. Adherends are modeled as Euler-Bernoulli beams. Both ransverse and axial deformation of adherends are considered in deriving the equations of motion. In the experimental part, the steel use Q235, the aluminium use 6016-T4 and the adhesive use ESP110 and AV138, epoxy resin. Dynamic responses of the joints are investigated using the hammer test technique, natural frequencies and model shapes obtained by using an accelerometer depended on the accelerometer location in the system, which is attributed to its mass contribution to the overall system mass. The investigates are also carried out using the finite element method(FEM) and simulated with ABAQUS. Both results show that resonant frequencies decrease with the slant angle increase.

Effect of Supports on Stress Distributions in the Adhesive Joints

The aim of this paper is to investigate the effect of supports on the actual stress distribution of the single-lap adhesive joints under tension using the three-dimensional finite element methods. Five layers of elements were used across the adhesive thickness in order to obtain an accurate indication of the variation of stresses. All the numerical results obtained from the finite element analysis show that the spatial distribution of all components of stress are similar for different interfaces though the stress values are obviously different. The results also show that most of the maximum stresses occur at the interface 1. It can be seen from the results that the stresses are concentrated near the left free ends of the adhesive layer while the centre region of the adhesive layer is mostly stress-free.

Strength prediction of adhesive joints after cyclic moisture conditioning using a cohesive zone model

This paper presents a methodology to predict the strength of adhesive joints under variable moisture conditions. The moisture uptake in adhesive joints was determined using a history dependent moisture prediction methodology where diffusion coefficients were based on experimental cyclic moisture uptake of bulk adhesive samples. The predicted moisture concentrations and moisture diffusion history were used in a structural analysis with a cohesive zone model to predict damage and failure of the joints. A moisture concentration and moisture history dependent bilinear cohesive zone law was used. The methodology was used to determine the damage and failure in aluminium alloy – epoxy adhesive single lap joints, conditioned at 50 °C and good predictions of failure load were observed. The damage in the adhesive joints decreased the load carrying capacity before reaching the failure load and a nonlinear relationship between the load and displacement was observed. Changes in crack initiation and crack propagation were also observed between different types of joints. The presented methodology is generic and may be applied to different types of adhesive joint and adhesive.

Influence of Mechanical Behavior of Adhesives on Shear Stress Distributions in the Single-Lap Adhesive Joints

This paper deals with the effects of mechanical behavior of adhesives on the shear stress distributions of single-lap adhesive joints under tension using the three-dimensional finite element analysis (FEA) technique. Numerical examples are provided to show the influence on the shear stresses of the joints using adhesives of different characteristics which encompass the entire spectrum of viscoelastic behavior. FEA solutions of the shear stress distributions in the adhesive layer have been obtained for four typical characteristics of adhesives. The results indicate that Young’s modulus and Poisson’s ratios of adhesives strongly affect the shear stress distributions of the joints.

Failure analysis of adhesively bonded joints in composite materials

The present paper is concerned with a phenomenological model to perform the failure analysis of composite adhesive single lap joints with arbitrary glued area. The theory is conceived for joints composed by highly resistant elastic adherends bonded with brittle–elastic adhesives. It is shown that, under certain conditions, the rupture forces (in the case of monotonic loading) and lifetimes (in the case of cyclic loading) of two joints with different glued areas can be correlated using a shape factor. Results from experimental static and fatigue testing of joints with carbon/epoxy laminates bonded with epoxy adhesive and different bonding areas are compared with model prediction showing a good agreement.

3-D FEM stress analysis and strength evaluation of single-lap adhesive joints subjected to impact tensile loads

The stress wave propagations and interface stress distributions in the single-lap adhesive joint under impact tensile loads are analyzed using the three-dimensional finite element method (3D-FEM) taking into account the strain rate sensitive of the adhesive using Cowper–Symonds constitutive model. It is found that the rupture of the joint initiates near the middle area of the edges of the interfaces along the width direction. In addition, the effects of Young's modulus of the adherend, the overlap length and the thickness of the adhesive layer, and the initial impact velocity of the impacted mass on the stress wave propagations and the interface stress distributions are examined. The characteristics are compared with those of the joint under static loads, which show the different properties. Furthermore, experiments are also carried out for measuring the strain responses and the joint strength. A fairly good agreement is observed between the numerical and the measured results. The strength of the single-lap adhesive joint, which is described using impact energy, is obtained between 5.439 and 5.620 J for the present joint.