Modulus Of Adherends Research Articles

Buckling of functional graded polymeric sandwich panel under different load cases

In the present paper, the buckling behaviors of adhesively bonded sandwich plates subjected to in-plane shear force, in-plane normal compression force, and out-of-plane distributed load were studied for both point supported concept and linear supported concept. The functionally gradient polymeric adherends and elastic, homogeneous adhesive were used in the assembly. The epoxy resin was used and two types of graphite powder materials were selected PAM96/98 and PV60/65 as filler. The graphite powders were added to the epoxy resin as 3%, 6%, 9%, and 12% vol. The structure and graphite distribution were investigated by light microscope and the elasticity modulus of adherends were predicted based on the image processing program. The influences of the type and volume of graphite powders on the buckling behavior were studied by finite element analyses. The critical buckling loads were predicted and their mode shapes were presented. The highest critical buckling load was determined in PV60/65 structure panels for three different load cases due to the fact that the PV60/65 graphite powder was compatible with epoxy resin.

Numerical Stress Analysis of Epoxy Adhesively Bonded Dissimilar Joint

A two-dimensional adhesively bonded dissimilar single lap joint model was analyzed under tension. An explicit closed-form solution was formulated by using MATLAB tool for analysis of shear and peel stresses distribution along the bondline under effect of variation of overlap length, adherend thickness ratio and adherend Youngs modulus ratio. The solution was formulated based on analysis of Bo Zhao et al. [2]. The bending moment at the edge joint of the Bo Zhaos solution was replaced by the bending moment at the edge joint that have been proposed by X. Zhao et al. [5] to compare the accuracy of solutions. The least stress intensities in dissimilar joint could be achieved with a suitable ratio of thickness and Youngs modulus of adherends.

Effect of substrate modulus on the fatigue behavior of adhesively bonded joints

The effect of the substrate material on mode-I fatigue behavior of a toughened epoxy adhesive system was examined in terms of the substrate stiffness and curing residual stress. It was found that a change in adherend material from aluminum to steel caused a reduction in the fatigue performance; i.e. the threshold energy release rate decreased and the crack growth rate increased for a given applied energy release rate. The possibility that these observations were a result of adhesive curing residual stresses was studied experimentally and analytically, but it was found that such effects were relatively small. Finite element modeling showed that the fatigue results could be explained in terms of an increase in the crack tip stresses and an enlarged plastic zone due to the greater modulus of steel compared with aluminum. The local influence of the adherend modulus proved to be much more significant than the global effect of the adherend stiffness (product of modulus and moment of inertia). The effects of adherend modulus are expected to diminish as the phase angle increases.

Application of beam mechanics to sensing the cure development of wood-phenolic joints by dynamic mechanical analysis

Modeling and optimizing of wood-based composite manufacture is playing a larger role in the design of processes and manufacturing equipment. In these models, internal temperature and moisture conditions are predicted with an aim towards predicting when polymeric cure is sufficient to avoid delamination. However, most cure kinetics models are focused on predicting the chemical state of the resin rather than the resulting mechanical properties. The objective of this research is to examine the feasibility of obtaining kinetic cure data using dynamic mechanical analysis (DMA). Dynamic three-point bending tests were conducted on a sandwich specimen of two wood adherends bonded with an adhesive layer. The specimen was cured using various isothermal and linear heating regimes. In addition, two commercial PF resins of different molecular weights distributions (labeled as PF-high and -low, respectively) were evaluated under different experimental conditions influencing moisture loss. Theoretically, the E′ ratio, defined as, R = E ′ max / E ′ min should be good parameter to evaluate bond development because it eliminates the variation in adherend modulus. However, this parameter was found to be sensitive to variables such as resin loading and changes in the adherend modulus due to moisture loss and thermal softening. The shear modulus and flexural storage modulus of the adhesive were calculated by an analytical solution. The values were in general agreement with the results obtained by parallel-plate rheometry. Overall, the sandwich beam was deemed to be simple in both sample preparation and measurement procedure for obtaining PF resin cure transitions and modulus development.

Three-dimensional finite element analysis of stress response in adhesive butt joints subjected to impact bending moments

The stress wave propagation and the stress distribution in adhesive butt joints of T-shaped similar adherends subjected to impact bending moments are calculated using a three-dimensional finite-element method (FEM). An impact bending moment is applied to a joint by dropping a weight. The FEM code employed is DYNA3D. The effects of the Young's modulus of adherends, the adhesive thickness, and the web length of T-shaped adherends on the stress wave propagation at the interfaces are examined. It is found that the highest stress occurs at the interfaces. In the case of T-shaped adherends, it is seen that the maximum principal stress at the interfaces increases as Young's modulus of the adherends increases. In the special case where the web length of T-shaped adherends equals the flange length, the maximum principal stress at the interfaces increases as Young's modulus of the adherends decreases. The maximum principal stress at the interfaces increases as the adherend thickness decreases. The characteristics of the T-shaped adhesive joints subjected to static bending moments are also examined by FEM and compared with those under impact bending moments. Furthermore, strain response of adhesive butt joints was measured using strain gauges. A fairly good agreement is observed between the numerical and the experimental results.

Modulus Graded Composite Adherends for Single-Lap Bonded Joints

The effect of spatial grading of adherend elastic modulus on the peak stress and stress distribution in the single-lap bonded joint is studied. Single-lap joint with various modulus grading profiles were studied and the results compared with the traditional uniform modulus adherends using linear elastic finite element analysis. Braided preform with continuously varying braid angle was fabricated and the variation of the braid angle measured to realistically evaluate the performance of adherend modulus grading in single-lap bonded joint. The peak stress, stress distribution and transverse displacement at the adhesive mid-thickness were used to compare between the different adherend modulusgrading. The maximum shear stress reduced by about 20% and the shear stress was more uniformly distributed in the adhesive for an actual case of adherend modulus grading. It was also noticed that the joint rotation wasminimum for thisactual case of adherend grading.

Three-dimensional finite element analysis of single-lap adhesive joints subjected to impact bending moments

This paper deals with the stress wave propagations and stress distributions in single-lap adhesive joints subjected to impact bending moments with small strain rate. The elastic stress wave propagation and the stress distribution in single-lap adhesive joints of similar adherends subjected to impact bending moments are analyzed using three-dimensional finite-element method (FEM). A three-point impact bending moment is applied to the joint by dropping a weight. FEM code employed is DYNA3D. The effects of Young's modulus of the adherends, the lap length, the adherend thickness and the adhesive thickness on the stress wave propagation at the interfaces are examined. It is found that the maximum value of the maximum principal stress, σ1, appears at the interface between the adhesive and the upper surface of upper adherend which is impacted. The maximum stress, σ1, increases as Young's modulus of adherends, the lap length and the adhered thickness increase. It is also found that the maximum stress, σ1 increases with decreasing adhesive thickness. In addition, experiments were carried out to measure the strain response of single-lap joints subjected to impact bending moments using strain gauges. A fairy good agreement was observed between the numerical and experimental results.

A Two-dimensional Stress Analysis and Strength of Single-lap Adhesive Joints of Dissimilar Adherends Subjected to External Bending Moments

The stress distributions of single-lap adhesive joints of dissimilar adherends subjected to external bending moments are analyzed as a three-body contact problem by using a two-dimensional theory of elasticity (plane strain). In the analysis, dissimilar adherends and an adhesive are replaced by finite strips. In the numerical calculations, the effects of the ratio of Young's moduli of adherends, the adherend thickness ratio and the adherend length ratio between dissimilar adherends on the stress distributions at the interfaces are examined. The results show that the stress singularity occurs at the ends of the interfaces, and its intensity is greater at the interface of the adherend with smaller Young's modulus. It is also noted that the singular stress is greater at the interface of the thinner adherend. It is found that the effect of the adherend length ratio on the stress singularity at the interfaces is very small. Joint strength is predicted by using the interface stress and it was measured by experiments. From the analysis and the experiments, it is found that the joint strength increases as Young's modulus of adherends and the adherend thickness increase while the effect of the adherend lengths on the joint strength is small. For verification of the analysis, a finite element analysis (FEA) is carried out. A fairly good agreement of the interface stress distribution is seen between the analytical and the FEA results.

Elastoplastic FEM Stress Analysis and Strength of Adhesive Butt Joints of Dissimilar Hollow Shafts Subjected to External Bending Moments.

Stress distributions and deformation of adhesive butt joints are analyzed by the elastoplastic finite-element method when the joints of dissimilar shafts are subjected to external bending moments. The effects of the ratio of Young's modulus of adherends to that of adhesive and the adhesive thickness on the interface stress distribution are investigated. Joint strength is predicted from using the elastoplastic interface stress distributions. As a result, it is found that the singular stress at the interface edges increases with an increase of the ratio of Young's modulus. Measurement of strains in joints and experiments on joint strength were conducted. The calculated results are in fairly good agreement with the experimental results. It is found that the joint strength of dissimilar shafts is smaller than that of similar shafts. A fracture of dissimilar adhesive shafts occurs at interface between an adhesive and an adherend which has a smaller Young's modulus. It is observed that joint strength increases as the adhesive thickness increases.

Two-Dimensional Stress Analysis of Single-Lap Joints Subjected to External Bending Moments.

The stress distributions of single-lap adhesive joints subjected to external bending moments are analyzed as a three-body contact problem by using a two-dimensional theory of elasticity. In the analysis, two similar adherends and an adhesive are replaced by finite strips, respectively. In the numerical calculations, the effects of the ratio of Young's modulus of adherends to that of adhesive and the adhesive thickness on the stress distribution at the interface are examined. As the results, it is found that the stress singularity occurs near the edges of the interface, and the peel stress at the edges of the interface increase with a decrease of Young's modulus of adherends. In addition, photo-elastic experiments are carried out. A fairly good agreement is obtained between the analytical and the experimental results.

Two-Dimensional Stress Analysis of Single-Lap Adhesive Joints Subjected to Tensile Shear Loads.

The stress distributions and the deformations in single-lap adhesive joints consisting of similar adherends are analyzed using a two-dimensional theory of elasticity when the joints are subjected to tensile shear loads. In numerical calculations, the effects of the ratios of Young's modulus and the thickness ratios between an adhesive and adherends on the stress distributions at the interfaces are examined. As the results, it is seen that the stress singularity caused at the edges of the interfaces increases with a decrease of Young's modulus of adherends. In addition, the stress distributions in joints are analyzed by the finite-element method. A fairly good agreement is seen between the analytical result and the result obtained by the finite-element method.

Two-Dimensional Stress Analysis and Strength Evaluation of Band Adhesive Butt Joints of Dissimilar Adherends Subjects to Tensile Loads.

The stress of band adhesive butt joints in which the interfaces are partially bonded, was analyzed using a two-dimensional, theory of elasticity in order to establish fracture criteria for the case in which the joints of dissimilar adherends are subjected to tensile loads. In the analysis, when the interfaces are bonded by an adhesive at two regions, the dissimilar adherends and the adhesive are replaced with finite strips. In the numerical calculations, the effects of the ratio of Young's modulus of adherends to that of adhesives, the thickness of the adhesives, the bonding area and position and load distributions on the stress distributions at the interfaces were demonstrated. In addition, with use of the stress distribution, a method for evaluating joint strength was proposed. As a result, it was observed that band adhesive joints were available when the bonding area and positions were varied taking into account external load distribution. For verification, experiments were performed on the strain of adherends and the joint strength. Analytical results were consistent with the experimental ones.

Two-dimensional stress analysis of adhesive butt joints subjected to cleavage loads

This paper deals with the two-dimensional stress analysis of adhesive butt joints subjected to cleavage loads. The purpose of the paper is to contribute to the establishment of fracture criteria of adhesive joints. Similar adherends and an adhesive bond are replaced with finite strips in the analysis. Stress distributions in adhesive joints are analysed using the two-dimensional theory of elasticity. The effects of the ratio of Young's modulus of adherends to that of an adhesive and the thickness of the adhesive bonds on the stress distributions are shown by numerical calculations. For verification, strains produced on adherends are experimentally measured and a photoelastic experiment is carried out. The analytical results are in fairly good agreement with experiment.

A two-dimensional stress analysis of band adhesive butt joints subjected to tensile loads. The case of finite strip adherends.

In this paper, the stresses of band adhesive butt joints, in which adhesive bonds were used partially at the interfaces, were analyzed using a two-dimensional theory of elasticity in order to determine the usefulness of the joints. In the analysis, similar adherends and adhesive bonds which were set at two or three regions were replaced with finite strips. In numerical computations, the effects of the ratio of Yound's modulus of adherends to that of adhesives, the thickness of the adhesives, the bonding area and position, and the load distribution on the stress distributions at the interface were shown. It was seen that band adhesive joints were effective when the bonding area and positions were varied with external load distributions. Photoelastic experiments and experiments concerning the strains of adherends were performed. The analytical results were fairly consistent with the experimental results.

A two-dimensional stress analysis of band adhesive butt joints subjected to external bending moments.

The stresses of band adhesive butt joints subjected to external bending moments, in which adhesive bonds were used partially at the interface, were analyzed using a two-dimensional theory of elasticity in order to establish the fracture criteria of joints. Similar adherends and adhesive bonds which were used at two or three regions at the interface were replaced with finite strips in the analysis. In numerical computations, the effects of the ratio of Young's modulus of adherends to that of adhesives, the thickness of the adhesive and the bonding area and positions on the stress distributions at the interface were shown. It was found that band adhesive joints were effective when the bonding area and positions were varied with external load distributions. The stress distribution near the singular point at the interface were expressed approximately. Photoelastic experiments and experiments concerning the strains of adherends were performed. The analytical results were fairly consistent with the experimental results.

Two-dimensional stress analysis of adhesive butt joint subjected to external bending moments. (The case where adherends are dissimilar materials).

In the present paper, the stresses of butt adhesive joints are analyzed by a two-dimensional theory of elasticity in order to establish the fracture criteria when dissimilar adherends are bonded by an adhesive. Dissimilar adherends and an adhesive are replaced with finite strips, respectively, and the analyses are done as a three body contact problem. In numerical computations, the effects of the ratio of Young's modulus of dissimilar adherends, the ratio of Young's modulus of adherends to that of an adhesive and the thickness of the adhesives are shown on the distributions at the interfaces of the joints. As a result, it is seen that the principal stress becomes maximum at the interface between the adhesive and the adherend having high Young's modulus. For verification, experiments are performed. Analytical results are in fairly good agreement with experimental ones.

Two-dimensional stress analysis of adhesive butt joints subjected to tear loads.

This paper deals with a two-dimensional stress analysis of adhesive butt joints subjected to tear loads. The purpose of the present paper is to contribute to an establishment of the fracture criteria of joints. Similar adherends and an adhesive bond are replaced with finite strips in the analysis. Stress distributions in adhesive joints are analyzed by using the two-dimensional theory of elasticity. The effects of the ratio of Young's modulus of adherends to that of the adhesive and the thickness of adhesive bonds on the stress distributions are shown by numerical computations. For verification, experiments are performed with respect to the strain of adherends. The analytical results are in fairly good agreement with the experimental ones.

Strength design of the thin walled butt joint bonded with adhesive resin between dissimilar adherends.

The effects of the mechanical properties of adherend materials on the strength of adhesive joints were studied by applying a tensile and torsional load to the tubular butt joints of dissimilar adherends. The specimen materials used in the experiment were carbon steel, copper, brass, aluminium alloy for adherends and epoxy resin for adhesive. The strength of the cured adhesive joint under the tensile load was compared with that without curing to investigate the effect of the difference in the coefficient of thermal linear expansion on the strength of the adhesive joints. The strength of the cured joints was higher than that of the non-cured joints. This showed that there was no remarkable influence of the coefficient of thermal linear expansion on the joint strength. The effects of ratio of Young's modulus on the joint's strength under tensile load decreased when the difference in Young's modulus of adherends was larger. This decrease of the joint strength was discussed on the basis of the analytical stress distribution in the inter face between adhesive layer and the adherend.

Strength evaluation of asymmetric single lap joints (3rd report, Effects of the mechanical properties of adherends)

The deformation and strength of single lap joints having adherends of dissimilar materials were investigated analytically and experimentally. The strain distributions of the joints of carbon steel and aluminum alloy boded with epoxy resin under tensile shear loads were analyzed by the finite element method. The analytical strain distributions coincided approximately with the experimental results. The analytical results of the strength were less than the experimental strength, because the analytical results predicted the initial cracking loads which were different from the final fracture loads. The Young's modulus of adherends and the adhesive lap length had much effect on the joint strength. The strength of joints of carbon steel and aluminum alloy had intermediate values between the strength of joints having carbon steel adherends and aluminum alloy adherends. The curing process of the adhesive resin improved the joint strength overcoming the difference of thermal properties in the adherends.

Strength Evaluation of Asymmetric Single Lap Joints : 3rd Report, Effects of Mechanical Properties of Adherends

The deformation and strength of single lap joints having adherends of dissimilar materials were investigated both analytically and experimentally. The strain distributions under tensile shear loads of the joints of carbon steel and aluminum alloy bonded with epoxy resin were analyzed using the finite element method. The analytical result was shown to coincide approximately with the experimental one. The analyzed strength was less than the experimental one probably because the former predicted the initial cracking loads whereas the latter predicted the fracturing loads which were different from the former. Young's moduli of adherends and the adhesive length had great effect on the joint strength. The strength of joints of carbon steel and aluminum alloy had valued intermediate between the strengths of joints having carbon steel adherends and aluminum alloy adherends. The curing process of the adhesive resin improved the joint strength overcoming the difference in thermal properties of the adherends.