Elastic Modulus Of Adhesive Research Articles

A numerical study on the bonding of the thin-walled and large-deformation composite components

Thin-walled and large-deformation composite components that need to be stowed and deployed as space deployable structures require a high bonding property. The purpose of this work is to study the failure mode and influence of scroll radius, adhesive elastic modulus, adhesive thickness, and layup angle on the stress of the adhesive layer and strain energy through a numerical method. A good agreement between experimental and numerical results was obtained verifying the numerical method. Firstly, results show that as the scroll radius increases, the shear and peel stress of the adhesive layer, as well as the strain energy, decrease and the failure of the adhesive layer is mainly peel failure. Furthermore, in addition to the shear and peel stress, the strain energy is also substantially affected by the ply angle. Considering the shear stress, peel stress, and strain energy, the [90/0]s ply becomes the best choice. The shear and peel stress increase with increasing adhesive elastic modulus. Lastly, an increase in adhesive thickness is found to decrease the shear and peel stress of the adhesive layer. However, the change in strain energy corresponding to the change in adhesive thickness is small. This study paves the way for the selection of bonding parameters of thin-walled and large-deformation composite components.

Effect of adhesive properties on the bond behaviour of externally bonded FRP-to-concrete joints

The influence of adhesive properties on the bond behaviour of externally bonded fibre-reinforced polymer (FRP)-to-concrete joints is the focus of this paper. First, FRP-to-concrete double-lap shear specimens were tested with different types of bonding adhesives. The test results indicate that when softer adhesives are adopted, the peak load, interfacial fracture energy and FRP effective bond length increase while the peak shear stress decreases. Then, a finite element (FE) model including the adhesive layer was proposed to further investigate the influence mechanism of the adhesive properties. A numerical parametric study indicates that the adhesive tensile strength, ultimate strain, elastic modulus and thickness all have varying degrees of impact on the bond behaviour of FRP-to-concrete joints. Finally, a bond-slip model that considers the adhesive elastic modulus is proposed based on experimental and numerical results. To validate this model, a comprehensive test database that includes 128 FRP-to-concrete joints with different adhesives was collected. The proposed model has been shown to have a higher accuracy and lower dispersion than the existing models for the prediction of the peak loads of FRP-to-concrete joints with different adhesives.

Adhesively bonded single lap joints with non-flat interfaces

A series of experiments and detailed finite element simulations were carried out to study the performance of single lap joints with non-flat interfaces loaded at a small angle to the mean bond plane. In the experimental part, fiber reinforced epoxy composite adherends with sinusoidal bonding surfaces (but no change to the exterior sample dimensions) were fabricated in a purpose-built mold. This construction method allowed the fibers to follow the sinusoidal profile for maximum strength. Then the sinusoidal surfaces were joined by a controlled-thickness layer of epoxy. Single lap joints with a flat interface were also fabricated using the same composite material and with the same overall shape. The experiments showed that the interface non-flatness has significant effect on the mechanical behavior and strength of the bonded joints. Finite element simulations of a simplified two-dimensional model with isotropic adherends were also carried out to estimate the distribution of shear and peeling stresses along the bonded joints, and the results were related to the experimental observations. Parametric variations were studied via FEA to highlight the role of interface shape, adhesive elastic modulus and a central void size on the distribution of stresses, and inherently the overall strength and behavior of the bonded joints.

Precision of the one-dimensional solutions for bonded double lap joints

The solutions that have been proposed for the stress state in bonded joints inevitably adopt a simplified description. By comparison with finite element results, it can be noticed that the analytical solutions reproduce in general terms the stress field, but in the end zones of the overlap mismatches are frequently observed. The present paper focuses the attention on the double lap joint. The classical solutions found by Volkersen (Construction métallique 4, 1965) and Hart-Smith (Technical Report NASA CR-11234, 1973) are compared with a solution, developed in this work, which accounts for bending in the external adherends and axial stiffness imbalance. Several cases of adherend to adhesive elastic modulus ratio, thickness and overlap length are considered; finite element results are taken for reference. It is found that the analytical solutions give acceptable results when the elastic modulus of the adhesive is much lower than that of the adherends. The Volkersen's solution, although it fulfils the zero-traction boundary condition, does not give better results than the others and often underestimates the peak values. It is likely that a better description of stress variation through the adhesive thickness could improve substantially the situation.

Stress Analysis of Shaft-Tube Bonded Joints Using a Variational Method

Functionally modulus graded bondline (FMGB) adhesives can be employed in bonded joints to reduce stress concentration and, hence, achieve higher joint strength. This study presents an analytical framework for the stress analysis of a shaft-tube bonded joint based on a variational technique which minimises the complimentary energy of the bonded system. This cylindrical assembly consists of similar or dissimilar adherends and a FMGB adhesive. The effect of functional grading of adhesive elastic modulus on the peak stresses and their distributions in the adhesive layer are studied. The joint with various modulus grading profiles is assessed and the results are compared with a conventional mono-modulus bondline (MMB) adhesive joint. Stress analysis indicates that the peel and shear peak stresses in the FMGB are much smaller and their distributions along bondlength are more uniform than those of MMB adhesive joints under the same axial tensile load. Numerical examples are provided to illustrate the effects of geometrical and material properties on the distributions and intensities of stresses in the bondline. Furthermore, optimal peel and shear strengths of the joint can be achieved by spatially controlling the modulus of the adhesive.

Dynamic response of a repaired composite beam with an adhesively bonded patch under a harmonic peeling load

The dynamic response of repaired composite beams under a harmonic peeling load was studied theoretically and experimentally. The repair method was based on removal of the damaged region and bonding a composite patch into the gap with adhesive. In the theoretical part, the equations of motion in the axial and transverse directions were derived assuming that the viscoelastic adhesive layer resists both peeling and shear stresses and both the patch and parent materials behave as Euler–Bernouli beams. The validity of the theoretical model for evaluating the dynamic response of repaired composite beams was examined with the results of the finite element model. The finite element results indicated that the deformation mechanism of the repaired composite beam depends on the adhesive elastic modulus. For low values of the adhesive elastic modulus, shear deformation in the adhesive layer is the dominant deformation mechanism and the proposed theoretical model replicated the results of the computational analysis. In the experimental part, the response of unidirectional fiberglass-reinforced epoxy composite specimens with various repaired patch lengths, thickness, and material properties were measured by hammer test technique using a non-contact laser vibrometer. The patch section was either the fiberglass-reinforced epoxy composite or E-glass fiber reinforced composites with various stacking sequences. The repairing patches were bonded to the composite beam with an epoxy. The experimental results were compared to those of the theoretical model and finite element analyses. The experimental results were related to the adhesive material properties, its loss factor and to the patch material properties.

複合はりの曲げおよびねじり振動試験による接着剤の動的弾性係数の比較測定

複合はりの曲げおよびねじり振動試験による接着剤の動的弾性係数の比較測定

Nonlinear finite element analysis of stress and strain distributions across the adhesive thickness in composite single-lap joints

A geometrically nonlinear, two-dimensional (2D) finite element analysis has been performed to determine the stress and strain distributions across the adhesive bond thickness of composite single-lap joints. The results of simulations for 0.13 and 0.26 mm bond thickness are presented. Using 2-element and 6-element mesh schemes to analyze the thinner bond layer, good agreement is found with the experimental results of Tsai and Morton. Further mesh refinement using a 10-element analysis for the thicker bond has shown that both the tensile peel and shear stresses at the bond free edges change significantly across the adhesive thickness. Both stresses became increasingly higher with distance from the centerline and peak near but not along the adherend–adhesive interface. Moreover, the maximum shear and peel stresses occur near the overlap joint corner ends, suggesting that cohesive crack initiation is most likely to occur at the corners. The dependence of stress and corresponding strain distributions on bond thickness and adhesive elastic modulus are also presented. It is observed that the peak shear and peel stresses increase with the bond thickness and elastic modulus.