Adhesive Fillet Research Articles

Analysis and design of adhesively bonded tee joints with a single support plus angled reinforcement

In this study, stress and stiffness analyses of adhesively bonded tee joints with a single support plus angled reinforcement were carried out using the finite element method. It was assumed that the adhesive had linear elastic properties. In actual bonded joints, some amount of adhesive, called the spew fillet, accumulated at the free ends of the adhesive layer; therefore, the presence of the adhesive fillet at the adhesive free ends was taken into account. The tee joints were analysed for two boundary conditions: a rigid base and a flexible base. In addition, each boundary condition was analysed for four loading conditions: tensile, compressive, and two side loadings. The stress analysis showed that both side loading conditions resulted in higher stress levels in the joint region in which the vertical plate and supports are bonded to each other, as well as in the adhesive layer in this region for both rigid and flexible base boundary conditions. In adhesively bonded joints, the joint failure is expected ...

Analysis and design of adhesively modified double-containment corner joints part 1

In this study, the stress and stiffness analyses of modified double-containment corner joints, in which plates are bonded at a right angle into slots of a corner support, were carried out using the finite element method. It was assumed that the adhesive and plates had linear-elastic properties. The presence of adhesive fillet at the adhesive free ends was taken into account. The corner joint was analysed for three loading conditions, two linear and one bending moment. It was found that the loading in the y direction is the most critical loading condition and that maximum stress concentrations occurred around the adhesive free ends. A detailed study of adhesive stresses showed that the peak adhesive stresses occurred at the lower free end of the left vertical adhesive layer-slot interface for the loading conditions Py and Mb respectively and the lower free end of the right vertical adhesive layer-slot interface for the loading condition Px. In addition, the effects of horizontal and vertical support lengths, slot depth and support thickness on the peak adhesive stresses and the overall joint stiffness were investigated. Dimensions of the corner support were given relative to the plate thickness.

Non-destructive evaluation of the adhesive fillet size in a T-peel joint using ultrasonic Lamb waves and a linear network for data discrimination

This paper describes a novel application of ultrasonic Lamb waves combined with network methods for data analysis for a non-destructive evaluation of the adhesive fillet size in the cusp of an aluminium T-peel joint. The ultrasonic signals were transmitted and received using a purpose-built cross correlator system, which generated filtered pseudo-random binary sequences tailored to excite s0 and a1 wave modes in the specimens. Signals received after propagation across the joint area were analysed in the modulus frequency domain by means of a standard fast Fourier transform. Simple statistical measures (such as mean and standard deviation) applied to peaks in the frequency spectra did not provide a robust basis for automatic discrimination between classes of bond fillet size, with 'recognition' success being of the order of chance alone. The most basic form of artificial neural network, the linear network, was then trained to recognize bond fillet radius as belonging to one of three categories of size. When presented with regions of bond fillet that were not included in its training data, it was able to 'recognize' fillet sizes with a success rate of 95%. The sensitivity of the method to experimental arrangements was examined by comparing the results obtained with well-collimated water-coupled transducers with those obtained by using mode-converting contact probes, which exhibited greater angular dispersion in the excited waves. Comparisons were made between different transducer excitations designed to excite s0 alone, a1 alone, s0 and a1 together and also a broadband excitation. Various training protocols for the network were also compared as were the results of output thresholding to minimize the number of wrong decisions made by the network. Overall we find that the best fillet size recognition performance was obtained with the broadband excitation applied to mode-converting wedge transducers set on either side of the bond.

Non-linear analysis and optimization of adhesively bonded single lap joints between fibre-reinforced plastics and metals

Abstract Non-linear finite element methods are applied in the analysis of single lap joints between fibre-reinforced plastics (FRP) and metals. The importance of allowing for both geometric and material non-linearities is shown. The optimization of single lap joints is done by modifying the geometry of the joint ends. Different shapes of adhesive fillet, reverse tapering of the adherend, rounded edges and denting are applied in order to increase the joint strength. The influence of the joint-end geometry is shown for different metal adherend/FRP adherend/adhesive combinations. The results of the numerical predictions suggest that with a careful joint-end design the strength of the joints can be increased by 90–150%.

Analysis and design of adhesively bonded corner joints: fillet effect

In this study, stress and stiffness analyses of corner joints with single corner support, consisting of two plates, one of which was plain and the other bent at right angles, have been carried out using the finite element method. In actual adhesively bonded joints, a certain amount of adhesive, called the spew or fillet, gathers around the free ends of the adhesive-adherend interfaces. A previous study neglected the effect of the adhesive fillet on the adhesive stresses. Therefore, in order to obtain more reliable and accurate results, the effect of the adhesive fillet on the adhesive stresses and the stiffness of the corner joint has been investigated. It was assumed that the plates and adhesive had linear elastic properties. The corner joint was analysed under three loading conditions, two linear and one bending moment. For loading in the y- direction and the bending moment the peak adhesive stresses occurred at the lower free end of the vertical adhesive layer-support interface, around the support corner inside the adhesive fillet, and at the lower free end of the vertical adhesive layer-vertical plate interface for the corner joint whose adhesive layer had a square end. The adhesive fillet also resulted in considerable decreases in the peak adhesive stresses for loading in the y- direction and the bending moment. However, for loading in the x- direction it caused small increases in the adhesive stresses, with the peak stresses again around the corner of the vertical plate inside the fillet. A second corner joint with double corner support, whose horizontal plate is reinforced by a support which is an extension of the vertical plate (designed to reduce the peel stresses which are critical for the first corner joint), was investigated. Although the adhesive fillet had the same effect on the stress distribution, the second corner joint resulted in considerable decreases in the adhesive stresses, particularly the peel stresses. A third corner joint with single corner support plus an angled reinforcement member was investigated as an alternative to the previous two configurations. The adhesive fillet had the same effect on the adhesive stresses around the adhesive free ends and the adhesive stresses were low compared to those of the previous types of corner joints and those in all corner joints whose adhesive layers had square ends. In the stiffness analysis, the effects of the geometry of the corner joints, particularly the adhesive fillet, were investigated under three loading conditions. The analysis including the adhesive fillet gave corner joints with higher stiffnesses for all loading conditions. For the three types of corner joint, the results were compared with those of the previous study and recommended designs were determined based on the stress analysis and on the overall static stiffness of the corner joints.

フィレットを持つ重ね合せ接着継手の応力分布と疲労強度

In adhesive bonded lap joints, stress in the adhesive layer is concentrated at the lap end because of difference in elastic moduli of constituents and abrupt thickness change. Hence, in order to improve the joint stength by reducing the stress concentration in the adhesive layer, it is practiced in industry to form it with a fillet of adhesive spew or to round the corners of the adherend. However, there are few studies on the fatigue strength charactristics of these improved adhesive joints.In order to investigate the relation between the fatigue stength of these joints and the local stress distribution near the lap end, a series of fatigue tests were conducted on the adhesive bonded lap joints with an adhesive fillet plus a rounded adherend, and the local stress near the adherend corner was analysed by FEM. Furthermore, the fatigue crack propagation behavior was observed with an optical microscope.As a result, It is confirmed that the fatigue strength of lap joints with different corner radii can be standardized by the maximum value of maximum shear stress near the lap end.

Heat-resistant thermoplastic/ chromic acid anodized Ti-6Al-4V single lap bond evaluation

Abstract Structural, heat-resistant thermoplastic adhesives were evaluated in single lap bonds. The amorphous thermoplastics tested were polyphenylquinoxaline, glass filled Ultem polyetherimide, unfilled Ultem polyetherimide, and Victerex polyethersulfone. The adherend was chromic acid anodized Ti-6Al-4V, tested unprimed and primed with Lica 44 titanate. Initial bond strengths were similar for all adhesives. In general, Lica 44 titanate primer did not affect bond strength. Bond strength was not influenced by 170°C ageing, but 232°C ageing did decrease bond strength when polyphenylquinoxaline was the adhesive. Failure occurred primarily in the adhesive fillet and propagated into the unprimed or primed anodic oxide/polymer interphase.

The Interaction of Adhesive Joint Strength and Adherend Cladding

Abstract The paper presents the results of an investigation concerning the effect of the cladding layer on the strength of a bonded joint. This has been carried out by combining the results from both experimental and analytical studies. The former involved a direct comparison of clad and unclad joints, providing data for the analytical work which was achieved through detailed non-linear finite element analysis of both clad and unclad configurations. Good estimates for failure strengths were found and, although adhesive yielding characteristics for both configurations were similar, the key to the differences in joint strength appear to be due to the presence of the adhesive fillet at the ends of the overlap.

The influence of local geometry on the strength of adhesive joints

This paper describes a two-part investigation into the effect of local geometry changes at the edges of the overlap in single lap joints. In the first part, finite element analysis has been used to model the effects on the stress distribution of geometry changes which are small in relation to the dimensions of the local geometry, in order to provide an improved model for failure prediction. The model used is that of an adhesive around a rigid corner, and the effect of rounding the corner has been considered. The second part deals with local geometry changes of the same order of magnitude as the dimensions of the geometry and their effect on joint strength. Three types of joint — one with a square-edged adhesive layer, one with a fillet of adhesive and one with an adhesive fillet plus a radiused adherend — were manufactured, tested and analysed. Improvements to the finite element models were also made following the results of part 1. It is found that finite element analysis is capable of predicting the significant strength increases that may be achieved in single lap joints by filleting the adhesive at the edges of the overlap and rounding the ends of the adherends.

Prediction of the fatigue strength of bonded joints between multi-directional laminates of CFRP

This paper presents the acquisition of fatigue properties of the constituent materials in bonded carbon fibre reinforced plastic joints, which, when used in a failure criterion with the stresses in the joint found by a finite element package, can predict the fatigue strength of that joint. Comparison with joint test results shows that initial failure (first crack), as predicted, occurs in the adhesive fillet, followed by shear failure in the nearest 0° ply in the composite bar. The latter failure site and mode can be predicted but the prediction of endurance from first crack to failure is beyond the scope of this paper.

Stress Analysis of Adhesive Bonded Tubular Lap Joints

Abstract The stresses in adhesive bonded tubular lap joints, subjected to axial and torsional loads, have been analysed using axisymmetric quadratic isoparametric finite elements. In the axial load case, the results are compared with a previously published closed-form solution and in the torsional case the results are compared with a closed-form solution presented here. The influences on the stress distributions of an adhesive fillet and of partial tapering of the adherends are also investigated, and an extension to the range of validity pf Goland and Reissner's second criterion is proposed.