Influence Of Adhesive Thickness Research Articles

Exploring strain rate variation in the adhesive layer during constant speed mode I fracture tests: Loading speed and test temperature effects

The existing literature primarily explores fracture energy concerning test rate. However, for numerical simulations and bonded joint design, understanding the fracture energy strain rate sensitivity is key, not test speed. Even at a constant speed in fracture tests, adhesive strain rate varies during crack propagation, complicating strain rate sensitivity analysis. The current study aims to comprehend the strain rate sensitivity of the fracture energy, as opposed to the loading rate sensitivity of two different polyurethane adhesives subjected to mode I loading conditions. The study experimentally examines strain rate variations under constant loading rates and investigates how test speed affects the strain rate in mode I fracture tests. The impact of testing temperature on the strain rate is also explored by performing tests at −30 °C and 23 °C. Digital image correlation (DIC) and tracking methods are employed to improve the understanding of strain rate characteristics in these tests. To analyse the effect of loading rate on strain rate, the tests were conducted at different speeds as well. The influence of adhesive thickness on the strain rate was also explored. It was experimentally found that the strain rate at the crack tip varies even at a constant loading rate. The variation in strain rate is mainly evident in tests performed at higher loading rates, where the strain rate range increases. The tests performed at low temperature revealed less variation of strain rate than the ones tested under the same loading rate condition at 23 °C. For the same adhesive, thicker bondlines are less likely to cause a substantial error in fracture energy results than thinner bondlines.

Influence of adhesive thickness and defect on mechanical property of adhesive bonded joint of flexible polymer substrate and cable for solar panel application

Flexible polymer substrate and flat polymer cable were adhesive bonded to fabricate the solar panel in the present study. The relationship between the adhesive thickness, mechanical properties and fracture morphologies of the joints were systematically investigated to figure out how the adhesive layers with different thickness affected the joints’ mechanical properties. The influence of the defects on the joint quality was also studied via an artificial defect introduction method. Adhesive failure accompanied with low tensile-shear strength was easy to occur to the joints with extremely thin adhesive thickness due to the weak boundary formation between the adhesive and the adherent. When the adhesive thickness increased, the joints started to show the cohesive failure with higher tensile-shear strength since the adhesive completely fill the surface crevices. The joints’ mechanical properties however decreased again with further increasing the adhesive thickness, owing to the generation of more defects and higher residual stress within the thicker adhesive layer. On the other hand, adhesive failure was more likely to occur around the defect, which significantly deteriorated the joints’ mechanical properties. The defect located in the center of the bonding area led to a larger adhesive fractured area, thereby having a greater impact on the mechanical properties in comparison to the same-size defect located in the corner or the marginal center.

Fatigue Crack Propagation Prediction of Corroded Steel Plate Strengthened with Carbon Fiber Reinforced Polymer (CFRP) Plates.

The purpose of this study is to investigate the mechanism of improving fatigue performance and the estimation model of fatigue life for corroded steel plate strengthened with CFRP plates. A new two-stage fatigue crack propagation prediction model for the corroded steel plate strengthened with CFRP plates was proposed; moreover, the identification of critical rust pits and the equivalent method of initial cracks, and the calculation method of stress intensity factor (SIF) values at the crack tip were established. The accuracy of the proposed model was verified by comparing the predicted and tested fatigue life of the corroded steel plate strengthened with CFRP plates. Finally, the proposed two-stage crack propagation model was applied to carry out a parameter analysis to investigate the effect of weight loss rate, equivalent initial crack size, adhesive thickness, CFRP stiffness and CFRP prestress level on the fatigue crack propagation of the corroded steel plate strengthened with CFRP plates. Results showed that the maximum depth and the average width of the rust pits were suggested to be taken as the equivalent dimensions of the initial semi-elliptical surface crack for the fatigue crack propagation prediction of corroded steel plate strengthened with CFRP plates. Increasing the weight loss rate of the corroded steel plate, the initial crack size or the adhesive thickness would accelerate the crack growth and reduce the fatigue life, whereas increasing the stiffness or prestress level of the CFRP plate would significantly reduce the crack growth rate and increase the fatigue life. The smaller the initial crack size, the more sensitive the crack propagation life was to the variation of equivalent initial crack size. The influence of adhesive thickness on the fatigue life was limited and convergent, and the application of prestressing could significantly improve the utilization rate of CFRP materials and the fatigue strengthening effect of the corroded steel plate.

Direct measurement of axial compressive strength of carbon fibers using multifilament method

AbstractTo measuring the compressive strength of carbon fibers accurately and effectively, a specially designed fixture was applied for directly measuring axial compressive strength of carbon fibers using T800HB‐12 K multifilament. Influence of adhesive thickness and specimen length on the testing results was investigated. Adhesive of epoxy effectively transferred compressive stress from the fixture to the specimen and provided enough support of multifilament rod from bending during compressive load. Typical shear failure for multifilament rod was realized for T800HB‐12 K carbon fibers during compression testing using the purposely designed fixture at adhesive thickness of 0.101–0.110 mm and test length of 2.0–3.0 mm. Compressive strength of about 2700 MPa with variation coefficient of 8% was obtained for T800HB‐12 K carbon fibers. The fixture and method established were capable for characterizing axial compressive strength of 1–24 K carbon fibers.

Simplified stress analysis of multilayered bonded structure under 1D-bar kinematics

Many current materials and structural systems are layered. The structural performances of these multilayered systems are dependent on interfaces, the presence of which is inherent to them. A methodology for the simplified stress analysis of such structures under 1D-bar kinematics is presented. The macro-element technique is used to solve the set of ordinary differential equations involved. A dedicated macro-element is formulated through the approximation of displacements fields by Taylor expansion power series. The predictions of the simplified stress analysis are in close agreements with those obtained by FE analyses. Finally, the influence of adhesive thickness and of the overlap length on the adhesive stress peaks is presented.

An improved four-parameter model on stress analysis of adhesive layer in plated beam

The prediction of stresses in an adhesive layer is helpful in revealing the mechanism of debonding failure in plated beams. This study proposes an improved analytical model for the stress analysis of an adhesive layer in a plated beam. The beam and the soffit plate are individually modelled as a single Timoshenko sub-beam with separate rotations, while the adhesive layer is modelled as a two-dimensional elastic continuum in plane stress, which considers different adherend-adhesive interface stresses. The internal forces of the adhesive layer are assumed to satisfy the Timoshenko beam theory, and the shear deformation and bending moment of the adhesive layer can be considered. The internal forces and displacements of the adhesive layer are fully considered in the displacement compatibility equations, and deformable interfaces are assembled so that the effect of interface stresses on local deformation is captured. Based on equilibrium equations and displacement continuity, the governing differential equations of beam forces are derived, and then the analytical solutions of interface stresses and stresses along the thickness of the adhesive layer are obtained. Comparisons of the results of the finite-element analysis and the existing four-parameter model solutions show that the present model is reasonable. The influence of adhesive thickness on stress distributions in adhesive layers is also investigated.

The effects of Al surface treatment, adhesive thickness and microcapsule inclusion on the shear strength of bonded joints

The influences of various Al surface treatments, adhesive thicknesses as well as the incorporation of synthesized microcapsules into epoxy adhesive on the shear strength of adhesive/ Al joints have been investigated using lap-shear tensile tests. First, the influence of adhesive thickness on the shear strength of joints has been presented. Then, the effects of various Al surface treatments on the surface roughness of Al and shear strength of joint have been researched. Atomic force microscopy was used to study the Al surface morphologies and textures. Finally the few micron-sized polymeric microcapsules were synthesized and the shear performances of microcapsule filled epoxy adhesives were inspected. It was observed that the HCl acid based etching increased both micro-roughness and nano-texture of the Al surface and led to the peak shear strength. Moreover, HCl-nitric acid treatment offered the maximum value for the cohesive failure. Capsule inclusions into the adhesive displayed different influences on the joint shear performances depending on the capsule morphology and the surface treatment of Al.

Ballistic Impact Simulation of Ceramic/Metal Armor Structures

The study presents a comparative numerical investigation on ballistic performance of ceramic/metal armor structures. 2D axisymmetric numerical model was developed for ballistic impact simulations using LS-DYNA ® finite element software. The armor structures included combinations of boron carbide (B 4 C), Al6061-T6 and 4340 steel constituents. The interfaces in the armor structure were modelled with an epoxy resin adhesive. In order to define proper material behavior, Johnson-Holmquist-Ceramics material model for B 4 C and Plastic-Kinematic material model for Al6061-T6, 4340 steel and epoxy resin was used . The armor structures were subjected to 7.62 mm ogive-nosed steel projectile impact. In the first section, the influence of back plate material on the ballistic performance of the armor structure for bi-layers ceramic/metal configuration (ceramic front face and metal back plate) was investigated for Al6061-T6 and 4340 steel materials under same thickness and areal density. In the second section, the effect of removing half thickness of the metal constituent from the back plate and placing on the front face was investigated for both Al6061-T6 and 4340 steel materials. Finally, the influence of adhesive thickness on the ballistic performance of the armor structure was investigated. Perforation response of the armor structures were examined in terms of residual velocity of the projectile and damage mechanisms of the armor structure.

胶层厚度对三点支撑反射镜面形的影响

胶层厚度对三点支撑反射镜面形的影响

Influence of adhesive thickness on high velocity impact performance of ceramic/metal composite targets

Influence of adhesive thickness on high velocity impact (HVI) performance of ceramic (Al2O3-99.5)/aluminium (Al5083 H116) composite targets is critically examined in this paper through numerical investigations. Detailed parametric studies are carried out by choosing a practical problem and for a range of adhesive thickness between 0.1mm and 1.5mm. Studies are focussed on normal impact of the composite target by ogive nosed projectile with a velocity of 830m/s. Numerical simulation is carried out by adopting the Lagrangian approach and an axisymmetric finite element model. Impact responses are compared in relative terms among different cases of analysis to highlight the role played by adhesive thickness. Various response parameters such as shear strain developed at the interface of adhesive layer, target deformation, energy transformation, depth of penetration and deflection profile of back plate are considered in the investigations. These response parameters are observed to be influenced to different degree by the adhesive thickness. In particular, the depth of projectile penetration into the aluminium back plate is found to have non-monotonic variation with the thickness of adhesive layer.

Influence of adhesive thickness on local interface fracture and overall strength of metallic adhesive bonding structures

Adhesive bonding structures are widely used in a variety of engineering fields. Their overall strength is dependent on the cohesive properties involving local interface fracture. In the present research, the influence of the adhesive thickness on the cohesive properties and the overall strength of metallic adhesive bonding structures are investigated, with the cohesive zone model employed to equivalently simulate the adhesive layers with various thicknesses. A theoretical approach has been developed to determine the cohesive parameters for the present model when the adhesive thickness is varied. And then some numerical examples are given to explore the adhesive thickness-dependence overall strength of the adhesive joints, followed by some comparisons with the existing experimental results. Furthermore, the variations of both the cohesive parameters and the overall strength with the various thicknesses are influenced by some intrinsic characteristics of adhesives, which are investigated finally. The results show that both the cohesive parameters and the overall strength of metallic adhesive bonding structures are much dependent on the adhesive thickness, and the variations of overall strength resulting from the various thicknesses have discrepancy due to the toughness and strain hardening capacity of adhesives.

Influence of adhesive thickness on the behaviour of bonded assemblies under shear loadings using a modified TAST fixture

This paper presents contributions of numerical modelling for the analysis of adhesively bonded assemblies for marine applications. Such applications are often characterised by relatively thick, 0.5 mm or more, adhesive joints and by a possible variability of the bond line thickness associated with large-scale structures manufactured in boatyard environment. Experimental and numerical analysis in the case of shear tests are proposed to study the influence of bond line thickness on the mechanical behaviour of the adhesive. In order to accurately analyse the complete non-linear behaviour of an adhesive in an assembly, specimens with low edge effects have to be used. An increase in the thickness of the bond line leads to an increase in the influence of the edge effects, computed under elastic assumption. As those numerical results are not able to completely analyse all the experimental observations, various 2D simulations, with refined meshes, taking into account the non-linear behaviour of the adhesive are proposed to complete the analysis. Even for bonded assemblies with low edge effects, computed under elastic assumptions, the analysis of the stress distribution throughout the thickness of the joint, taking into account the non-linear behaviour of the adhesive underlines that an increase in the bond line thickness leads to an increase in equivalent plastic deformation close to the free edges. This property can explain that an increase in the bond line thickness can lead to a reduction in the transmitted load associated to crack initiation.

1406 弾性接着突合せ継ぎ手の疲労強度に及ぼす接着層厚さの影響(OS14-2 締結・接合部のプロセスと信頼性評価-接着接合-)

1406 弾性接着突合せ継ぎ手の疲労強度に及ぼす接着層厚さの影響(OS14-2 締結・接合部のプロセスと信頼性評価-接着接合-)

Influence of adhesive thickness and filler content on the mechanical performance of aluminum single-lap joints bonded with aluminum powder filled epoxy adhesive

The objective of this study was to develop information on the influence of adhesive thickness and aluminum filler content on the mechanical performance of aluminum joints bonded by aluminum powder filled epoxy. The adhesive strength of the joints was determined by utilizing the single-lap shear test. The influence of adhesive thickness and aluminum filler content on stress distribution within the adhesive was also analyzed by finite element method (FEM). Both FEM analysis and the experimental investigation show that in general adhesion strength decreases as the thickness of the adhesive increases. It is observed from the predictions (FEM simulations) that the stress level increases at the adhesive–metal substrate interface as the aluminum filler content in the adhesive increases. Experimental results show that epoxy adhesive retains its strength up to the 50 wt% aluminum filler content. The joints fail in cohesive mode (failure within the adhesive) due to the high stress levels generated in the adhesive, which indicates that the adhesion to the metal surface is stronger than that of the interior part of the adhesive.

The influence of adhesive thickness on bonding strength of the new bonding system -Tokuyama Bond Force.

The influence of adhesive thickness on bonding strength of the new bonding system -Tokuyama Bond Force.

Performance of butt strap joints for marine applications

The use of adhesive as a structural fastener is progressively taking place in shipbuilding. However, a series of issues needs to be looked at such as ageing and influence of the tolerance in the adhesive application in order to enhance the knowledge of this technology and reinforce its use in this industry. This paper hence presents the work carried out on butt strap adhesive joints bonding metallic adherends. The influence of adhesive thickness under different ageing conditions on the performance of the joints was investigated. Finite element analysis was carried out to model the joint behaviour taking into account geometric non-linear effects to explain the mechanisms leading to failure. Different failure modes were identified, depending on the level of adhesive thickness. The finite element analysis confirms experimental observations that failure initiated at the horizontal adhesive free surface. Accelerated ageing of the joints suggests interfacial degradation at the steel interface at the edges of the joint overlap.

Numerical investigation of the influence of material properties and adhesive layer thickness on the heating efficiency of microwave curing of an adhesive‐bonded joint

AbstractIn the process of microwave curing of an adhesive‐bonded joint, both the adhesive layer and the adherends affected the heating efficiency of the joint. As an extension of previous studies, the influences of changing the properties of the components of the joint on the heating efficiency were predicted by simulations that were based on the numerical model developed previously. The influence of adhesive thickness was also studied. The properties that directly affected power dissipation and heat loss of the adhesive layer were found to be important to the heating efficiency of the process. The heating rate was also sensitive to the thickness of the adhesive layer. Polym. Eng. Sci. 44:1414–1418, 2004. © 2004 Society of Plastics Engineers.

The interrelationships between electronically conductive adhesive formulations, substrate and filler surface properties, and joint performance. Part I: the effects of adhesive thickness

Electronically conductive adhesives (ECAs) have received a great deal of attention for interconnection applications in recent years. Even though ECAs have excellent potential for being efficient and less costly alternative to solder joining in electronic components, they still possess a number of problems with respect to durability and design to meet specific needs. One of the issues that requires understanding is regarding the optimum adhesive thickness (AT) to be used. This study addresses this issue in relation to the formulations of the conductive adhesives and their interactions with adherend surfaces. For this purpose, two different adherends varying in surface characteristics were utilized along with three different conductive adhesive formulations with varying particle loadings, and shapes and sizes of conductive nickel fillers. Joints were also prepared with two different AT values, to gain insight into the influence of AT on the joint strength, deformation and joint conductivity. As the AT was increased, only a small reduction in failure load and ultimate displacement values were observed with unetched adherends. With etched adherends, however, a small increase in joint stretchability was evident with higher adhesive thickness tested at a lower crosshead speed. When the AT was increased, we also noted a corresponding increase in the initial joint resistance.

An Analytical Model of the Mechanical Behaviour of Elastic Adhesively Bonded Joints

Abstract Contact and adhesion between two elastic solids bonded by a thin elastic adhesive are considered. The peculiar case of a rigid flat cylindrical punch being adhered to an elastic layer is considered. In order to evaluate the influence of adhesive thickness on the mechanical behaviour of the bonded solids, an approximate solution of the contact problem is derived, using the Ritz method. Comparison of the analytical solution with FE calculations shows a good convergence towards the asymptotic value when the ratio of the punch radius to the layer thickness is greater than 4. Numerical simulation reveals a strong effect of the adhesive compressibility, for a thin adhesive. This effect is assessed quantitatively from a double asymptotic expansion of the analytical solution. Lastly, the rupture stress is evaluated as a function of the adhesive thickness, from the knowledge of the solution of the contact problem: the asymptotic value for a very thin adhesive is determined independently.