Effect Of Adhesive Layer Thickness Research Articles

Effect of Adhesive Layer Thickness and Slant Angle on Piezoelectric Bonded Joints

Piezoelectric materials have found their parts in numerous manufacturing applications such as transducers and sensors. Piezoelectric material shows anisotropy; in addition, its elastic field and electric field are integrated. The analysis of piezoelectric materials has obtained great interest among researchers with the development of smart structures. It is significant to explain the distribution of stress and electric displacement fields along the bonded edge. It has never been obvious how stress singularity and electric displacement fields are distributed at the vertex of piezoelectric dissimilar material joints. Stress and electric displacement distribution near the vertex along the interface of piezoelectric boned joints are investigated in this present research. Numerical analysis of piezoelectric dissimilar material joints is carried out by using Abaqus FEA software. From the numerical analysis, it is observed that stress, displacement, electric potential, electric displacement field evolvement along the interface edge rises with the increment of adhesive layer thickness and slant angle. So, a thin adhesive layer thickness and small slant angle are more reliable for operation.

Temperature dependent fatigue crack growth in electrical steel laminates with μm-thick epoxy layers

The effect of adhesive layer thickness on monotonic roll peel strength and fatigue crack-growth kinetics was investigated for electrical steel laminates with bond line thickness values ranging from 7 to 48 μm. Roll peel strength was increasing with epoxy layer thickness up to 20 μm. In contrast, roll peel strength was leveling at higher thickness values. The fatigue fracture mechanics approach in mode I delivered an equivalent ranking such as roll peel testing. However, energy-based fracture mechanics analysis was much more sensitive than monotonic roll peel testing, also at thicker bond lines. The different failure modes were correlated with the plastic deformation zone size developing at the propagating crack. In case of a constrained plastic zone, cohesive failure mainly within the epoxy layer was ascertained. In contrast, interfacial failure and interestingly also a better fatigue crack growth resistance was deduced for a weakly or non-constrained plastic zone. Regarding the temperature dependency, an enhanced fatigue crack resistance was obtained at 60 °C. At this temperature about 50 °C below the maximum of the loss factor of the epoxy adhesive, the effect of epoxy layer thickness was much smaller than at 23 °C. At testing temperatures slightly below or above the glass transition temperature, the fatigue crack propagation rate was a factor of 10 to 100 higher.

Fracture and structural performance of adhesively bonded 3D-printed PETG single lap joints under different printing parameters

The present study, deals with fracture behavior of adhesively bonded 3D-printed joints. Polyethylene terephthalate glycol (PETG) is used to print standard specimens with different printing parameters (raster angle, raster width, and layer thickness) using fused deposition modeling (FDM) process. Moreover, adhesive layer with different thicknesses is employed to determine effects of adhesive layer thickness on the structural integrity of 3D-printed joints. By a series of tensile tests on the single lap joint specimens, influence of above-mentioned 3D printing parameters on the mechanical behavior of PETG joints is determined. Moreover, numerical study was conducted to verify experimental results and provide enhanced knowledge on fracture behavior of these types of joints. The nonlinear 3D finite element model of the joint supports mechanical characteristics of both 3D-printed adherends and adhesive materials. The effect of above mentioned 3D printing parameters in stress distribution and failure behavior of the joints are examined and reported. Considering a growing interest in FDM 3D printing technology in manufacturing and numerous applications of adhesively bonded joints, reported results are beneficial for future developments of new designs of 3D printed adhesively bonded products with a higher strength and better structural performance.

Experimental Study on Crack Characteristics of Damaged Reinforced Concrete Beams strengthened with CFRP

The bending tests of 2 control beams and 6 damaged beams strengthened with CFRP (DBSC) were carried out to study the effects of adhesive layer thickness, number of CFRP layers and reinforcement ratio on crack characteristics of DBSC. The test results show that the crack development of the DBSC is accelerated and the crack resistance of the DBSC is reduced compared with the intact beam. With the increase of the thickness of the adhesive layer, the crack development of the DBSC is slowed down and the crack resistance is improved. Increasing the number of CFRP layers is helpful to restrain the crack development of DBSC under high load level. The increase of reinforcement ratio can significantly improve the crack resistance of DBSC.

The Effect of Adhesive Layer Thickness on Joint Static Strength.

One of the most relevant geometrical factors defining an adhesive joint is the thickness of the adhesive layer. The influence of the adhesive layer thickness on the joint strength has not been precisely understood so far. This article presents simplified analytical formulas for adhesive joint strength and adhesive joint coefficient for different joint loading, assuming, inter alia: linear-elastic strain of adhesive layer, elastic strain of adherends and only one kind of stress in adhesive. On the basis of the presented adhesive joint coefficient, the butt joint was selected for the tests of the influence of adhesive thickness on the adhesive failure stress. The tests showed clearly that with an increase in the thickness of the tested adhesive layers (up to about 0.17 mm), the value of their failure stress decreased quasi linearly. Furthermore, some adhesive joints (inter alia subjected to shearing) may display the optimum value of the thickness of the adhesive layer in terms of the strength of the joint. Thus, the aim of this work was to explain the phenomenon of optimal adhesive layer thickness in some types of adhesive joints. The verifying test was conducted with use of single simple lap joints. Finally, with the use of the FE method, the authors were able to obtain stresses in the adhesive layers of lap joints for loads that destroyed that joints in the experiment, and the FEM-calculated failure stresses for lap joints were compared with the adhesive failure stresses determined experimentally using the butt specimens. Numerical calculations were conducted with the use of the continuum mechanics approach (stress-based), and the non-linear behavior of the adhesive and plastic strain of the adherends was taken into account.

Basic study on improvement of plastic drape adhesion for surgery: effect of adhesive layer thickness on drape detachment from wound edge.

Plastic drapes are used in surgery for a wide range of purposes, but currently marketed drapes often become detached from the wound edge during surgery. The purpose of this study was to determine the appropriate adhesive layer thickness for optimal peel and shear strength and the smallest peeled area to improve surgical drape wound adhesion. Thirty-two rats were randomly assigned to four groups of different adhesive layer thickness (50, 100, 300 and 800-1000 μm). The rats were anaesthetized, and drapes were applied to the dorsal chest. After incision, the peeled area was visualized by dropping ink in the wound site to measure the peeled area over time. All drapes peeled off from the wound edge, and the peeled area increased over time. The peeled area decreased in the order of 50 μm > 100 μm > 800-1000 μm > 300 μm. It is possible to control the peeling of plastic drapes during surgery by limiting the peeled area at the time of cutting. Three-hundred micrometres is the suitable adhesive layer thickness to minimize the peeled area at cutting.

Effect of adhesive thickness on the strength of steel-composite joints aged in wet environment

This paper presents the effect of adhesive layer thickness on the static strength of adhesively bonded steel-glass fiber-reinforced unsaturated polyester resin (GFRP) lap joints after being aged in water at a temperature of 60°C for 15 days. The adhesive thickness was varied from 0.1 mm to 0.5 mm. It was found that for the dry joints, the static strength increased with the increase of adhesive thickness. However, in wet condition, water really had a significant detrimental effect on the strength of the joints, as most of the strengths of wet joints were much lower than those of the dry joints. In dry condition, mode of failure changed from interfacial (at the adhesive thickness of 0.1 mm) to mix failure; however, for the wet joints; most of failures were at the interface of adhesive/steel.

Failure behaviour of the adhesive layer and angle ply composite adherends in single lap joints: A numerical study

In the last decades, composite materials have been increasingly used in advance engineering fields such as aerospace and automobile industries due to their advantages in terms of stress concentrations, structural weight and manufacturing. Joining composite parts in such applications has been increasingly achieved by adhesives compared to welded, riveted or bolted connections. Mechanical testings of adhesively bonded composite joints are often time consuming and expensive due to a number of parameters involved and their analytical modellings are complicated. Therefore, numerical analysis is increasingly used in recent years to overcome these limitations. In this work three-dimensional FE modelling of the single lap joints (SLJs) of angle ply composite adherends subjected to tensile loading was developed using ABAQUS/Explicit. Cohesive zone model was adopted for the modelling of damage in the adhesive layer. The continuum damage mechanic model implemented via a user defined VUMAT subroutine was used to model the intraply damage in composite adherends. The model accounted for the damage initiation, the damage evolution, and the nonlinear shear behaviour of the material. Experiments of the SLJs of [±10]5s, [±20]5s, [±45]5s and [±55]5s adherends under tensile loading were performed. The adherends were manufactured from glass reinforced polymer matrix and the adhesive layer was AF163-2K. For verification of the developed model, numerical results were compared with those of the experiments mentioned above. The SLJs of [±10]5s and [±20]5s adherends failed due to failure in the adhesive layer and those of [±45]5s and [±55]5s failed mainly due to failure in the adherends. The peel and shear deformation modes in the adhesive layer were invoked in different ways for different SLJ configurations. The effects of adhesive layer thickness and the overlap length on the response of the SLJ were investigated in detail.

Evaluation of adhesive scarf joint strength by using singular stress field of small interface crack

In the present study, the adhesive strength of scarf joint is examined by using the stress intensity factor of the fictitious small interface crack. The stress intensity factor of small crack near the interface edge is dominated by the singular stress field of the interface corner. In this study, to evaluate the joint strength, small crack is assumed at the interface corner of the scarf joint. The stress intensity factor of the interfacial crack is calculated by changing the thickness of the adhesive layer and the scarf angle. By using the experimental fracture strength of the scarf adhesive joint specimens under tension, the values of the critical stress intensity factor are calculated. From the analysis result, when the combination of adhesive materials and the scarf angle are fixed, the critical stress intensity factors of the small interface crack are constant value irrespective of the adhesive layer thickness. Therefore, the adhesive joint strength can be evaluated as the constant stress intensity factor of small interface crack. In addition, it is possible to evaluate easily the stress intensity factor by using the dimensionless coefficients depending only on the material combination when the crack length is sufficiently smaller than the thickness of the adhesive layer. The effects of adhesive layer thickness and adhesion angle of scarf joint specimen were discussed and the effectiveness of the proposed method was indicated.

Elastic constants for adhesively bonded corrugated core sandwich panels

In this paper, the adhesively bonded corrugated core sandwich panel is introduced and its elastic properties are discussed. Due to the relative displacement and rotation between face and core plates in adhesive joints caused by adhesive layer distortion, traditional elastic constants with considering both face and core plates to be fastened to each other are no longer fit for adhesively bonded sandwich panels. Therefore, its elastic constants with effect of adhesive layer distortion have been derived and presented in this paper. By submitting these elastic constants into closed-form solution, the response of simply supported sandwich panel under uniform load with small deflection is calculated which agrees well with 3D FEM analysis. Lastly, with the elastic constants, the effects of adhesive layer thickness and its elastic modules on both transverse shear stiffnesses with different shapes and dimensions are further studied and discussed.

Proposal of Method to Evaluate Adhesive Layer Strength under Multiaxial Stress State and Investigation on Effect of Adhesive Layer Thickness

Proposal of Method to Evaluate Adhesive Layer Strength under Multiaxial Stress State and Investigation on Effect of Adhesive Layer Thickness

Effect of Adhesive Layer Thickness on the Shear Strength of Adhesively Bonded Steel Joints in Wet Environment

The paper presents the static strength of adhesively bonded steel joints aged in deionized water at a temperature of 60°C for 15 days at various adhesive thicknesses from 0.1 mm to 0.5 mm. Water uptake and the bulk adhesive tensile properties after aged in the same environment as the joints were also presented. It has been shown that water diffusion into the adhesive is non Fickian. The absorbed water in the adhesive significantly decreases the mechanical properties and it affects the static strength of the bonded steel joints. The effect of water is shown to be significant when the adhesive thickness is thicker than 0.2 mm as the static strength decreases sharply. This information is useful when designing the adhesive joints using thick adhesive layer exposed in moist environment.

Experimental Verification of Effect of Adhesive Layer Thickness Used for Strain Gauge Mounting

Strain measurement from the strain gauge is partially affected by carrier and adhesive materials and their thickness. Effect of adhesive layer thickness has been addressed in this paper. Well characterized tensile experiments have been conducted using Al 6061-T6 specimens attached with strain gauges at mid length of the specimen and strain gauges are attached with different materials namely epoxy and polyurethane to understand the effect of adhesive layer thickness in strain measurement. The strain at a location has been noted for one particular adhesive layer thickness value (0.13 mm) and similar experiments have been carried out with different adhesive thickness values (0.16 mm, 0.18 mm and 0.26 mm). The results obtained from experiments have been compared with analytical results from Basic Strength of Materials approach. Good agreement is seen between the experimental and analytical results. It has been observed that the thickness of the adhesive layer plays significant role for getting accurate strain.

On the intralaminar and interlaminar stress analysis of adhesive joints in plated beams

An improved bimaterial adhesive joint model is proposed for the intralaminar and interlaminar stress analysis of adhesively-bonded interfaces in plated beams with thin or moderately thick adhesive layer. To overcome the limitations or unreasonable assumptions in the existing theoretical joint models, both the shear and normal stresses along two adherend–adhesive interfaces are assumed to be different in the present model, and the adhesive layer is modeled as a simplified 2-D elastic continuum. Deformable interfaces are assembled to establish the continuity conditions between the adherend–adhesive interfaces, and the local deformations near the end of the adhesive layer are fully captured. The longitudinal and transverse displacements of the adhesive layer are introduced as two new independent parameters, and the missing “degrees of freedom” in the conventional elastic foundation models are retrieved. Differential governing equation of an adhesively-bonded bi-layer beam is established, and explicit closed-form expressions of beam forces and interface stresses are derived. Comparisons of the present solution with the existing elastic foundation models as well as the full 2-D continuum elastic solutions by the finite element analysis are conducted to validate the presented model. Parametric studies are then conducted to reveal the roles of the adhesive thickness and local interface deformations on the stress distributions both along the adherend–adhesive interfaces (interlaminar) and through the adhesive layer thickness (intralaminar), from which a feasible measure to reduce the strain or stress concentrations is obtained. The present improved adhesive joint model in plated beams sheds light on the effect of adhesive layer thickness in bimaterial bonding assembly and provides a better understanding of potential interface debonding initiation and its propagation path.

Effect of Adhesive Layer Thickness and Drug Loading on Estradiol Crystallization in a Transdermal Drug Delivery System

The effects of adhesive layer thickness and drug loading on estradiol crystallization were studied in a drug-in-adhesive patch. Patches containing different estradiol loadings (1.1% and 1.6% w/w) in different thicknesses (45, 60, and 90 μm) were prepared by coating of a homogenous mixture of adhesive solution and the drug on a siliconized release liner by a film applicator. After drying, the film was laminated on a Poly(ethylene terephthalate) backing layer and cut into appropriate size. Release tests were performed using thermostated Chien-type diffusion cells. Cross-section of the patches was observed by optical microscopy. Scanning electron microscopy was done for surface analysis of the patches after drug release test. Crystal formation was not expected in the adhesive layer based on the linear free-energy relationship formalisms however; crystalline regions were observed in different locations through the thickness of the patches. These regions were significantly more discontinuous in 45 μm samples which elucidated the effective role of adhesive layer thickness in drug crystallization. Extensive crystallization observed for thicker patches was attributed to the strong crosslinking capability of estradiol hemihydrate. Drug release study confirmed some of the crystallization results. No significant increase was observed in the burst release with increasing in thickness from 45 to 60 μm which can be attributed to the severe increase in the crystallization extent. Also, formation of a crystalline layer near the releasing surface and more discontinuous pattern of the crystals in some samples was confirmed by investigation of the drug release curves.

Experimental and Analytical Investigations of the Dynamic Response of Adhesively Bonded Single Lap Joints

Dynamic response of single lap joints, subjected to a harmonic peeling load is studied theoretically and experimentally. In the theoretical part, dynamic response of a single lap joint clamped at one end and subjected to a harmonic peeling load at the other end is investigated. Adherents are modeled as Euler-Bernouli beams joined in the lap area by a viscoelastic adhesive layer. Both axial and transverse deformations of adherents are considered in deriving the equations of motion. The effects of adhesive layer thickness, mechanical properties and its loss factor on the dynamic response of the joint are investigated. Furthermore, effects of defects such as a void in the lap area on the dynamic response of the joints are studied. The results showed that frequencies where peak amplitudes occurred were little dependent on the adhesive loss factor. However, peak amplitudes reduced for joints with a higher adhesive loss factor. Furthermore, the results indicated that for the joint geometries and properties investigated the system resonant frequencies were not affected by the presence of a central void covering up to 80% of the overlap length. In the experimental part, single lap joints were fabricated using 6061-T6 Aluminum. Adherents were joined together using Hysol EA 9689 adhesive film. Joints with various central voids were manufactured by removing adhesive film from the desired area of lap joints prior to bonding adherents. Dynamic responses of the joints were investigated using the hammer test technique. The system response was measured using both an accelerometer and a noncontact laser vibrometer. The natural frequencies of the joints obtained by using the laser vibrometer were very close to those obtained theoretically. However, natural frequencies obtained by using an accelerometer depended on the accelerometer location in the system, which was attributed to its mass contribution to the over- all system mass. A central void covering less than 80% of the overlap length had little effect on the system resonance frequencies. This was in agreement with the theoretical results. In contrast total system-damping ratios were a function of the void size. Joints without a void exhibited higher damping.

Adhesive failure analysis of pressure-sensitive adhesives

In this article we use a linear elastic fracture mechanics approach to characterize the adhesive performance of two commercially available pressure-sensitive adhesives (PSAs). An axisymmetric adhesion test involving the contact of a spherical indenter with a thin adhesive layer is used to generate “tack” curves for both adhesives. These curves describe the relationship between the normal loads and displacements during the test. Adhesive failure is understood in terms of crack propagation at the indenter/adhesive interface. We investigate the effects of adhesive layer thickness and crosshead velocity on the tack curves. Using fracture mechanics equations developed for thin layers, we show that the energy release rate is a unique function of the crack velocity for a given adhesive. Based on the tack curves and energy release rates, we discuss the coupling of the bulk and interfacial properties that produce the large adhesion energies typical of pressure-sensitive adhesives. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3455–3472, 1999

Effect of adhesive layer thickness on fatigue strength of adhesively bonded butt, scarf and butterfly type butt joints

Fatigue tests under multiaxial stress conditions were conducted for the three types of butt, scarf and butterfly type butt joints in a variety of scarf angle and adhesive layer thickness

Effect of adhesive layer thickness on the bond strength of a zinc polycarboxylate dental cement

This study reports the effect of varying the thickness of a commercial zinc polycarboxylate dental cement on its adhesion in a metal-to-metal single lap joint. The thickness was controlled externally in a specially designed apparatus, rather than by the inclusion of isodimensional glass spheres, as has been done previously. The results show that both the tensile shear bond strength and the mode of failure of the cement are influenced by the thickness of the cement layer in the bonded joints. Hence, these results confirm previous findings that there is an optimum thickness for the zinc polycarboxylate layer. They also show that failure is more likely to be cohesive with thicker layers. The optimum thickness of the adhesive layer was 205 μm for the particular cement studied, PolyF Plus (De Trey, Dentsply, Weybridge, Surrey, UK), for which the average shear bond strength was found to be 4.03 MPa. Using stress analysis, the maximum shear and tensile stresses, τ 12(max) and σ 11(max), have also been obtained. These analyses showed that joints failed at the interface between the cement layers and the lap joint at adhesive layer thicknesses of below 100 μm. This resulted from the high stress concentrations in bonded joints with thin adhesive layers. On the other hand, thicker joints failed cohesively within the adhesive layer because of greater contributions from tensile stresses in these joints.