T-peel Joint Research Articles

Investigating strength increasing modifications to a friction stir welded AA7075 T-peel joint’s exit location: a modeling led study

Investigating strength increasing modifications to a friction stir welded AA7075 T-peel joint’s exit location: a modeling led study

Effect of overlap support characteristics on peel strength of weld-bonded joints

Bonded joints normally have a low peel tensile strength, since the stresses are concentrated on the small bond line. It has been proposed that adding a weld-bonded overlap support to the T-peel joint will enhance its peel strength tremendously. Since this support may increase the weight of the joint, a trade-off between weight increase (material type and thickness) and improved peel strength must be made. The aim of the present work is to investigate the effect of the overlap support characteristics (material and thickness) on the stress distribution of the T-peel joint. Different materials with different thicknesses are considered in order to strengthen the T-peel joint. A finite element technique was used for evaluating the current models. The results showed that the peak stress decreases with increasing thickness and stiffness of the overlap support.

Design a single overlap support plate for bonded and weld-bonded T-peel joints

In this study, a T-peel joint test is used to evaluate the resistance of bonded and weld-bonded joints to a peeling load. Bonded and weld-bonded peel joints have poor strength with respect to peeling loading. In the current study, experimental methods are proposed to study the strength enhancement by introducing a single overlap support for a T-peel joint. The results indicate that the peel strength enhancement increases significantly with the introduction of a single overlap support. Also, the strength enhancement further increases with increases in the overlap support length.

Enhanced layerwise model for laminates with imperfect interfaces – Part 1: Equations and theoretical validation

The aim of this paper is the enhancement and validation of a layerwise model applied to the analysis of laminates with thin layers of an elastic–plastic adhesive. The thin adhesive layers are modelled as imperfect interfaces across which displacement discontinuities exist. In a previous paper, the constitutive equations of the imperfect interfaces were empirically established without following the layerwise logic. The model equations are revisited and a solid theoretical justification of the new enhanced equations is obtained by making use of the Hellinger–Reissner functional. A theoretical validation of the model is performed by comparing its predictions to those of a solid finite element resolution in the case of a T-peel joint. The results of the enhanced version of the model are very accurate whereas those of the previous version are erratic for the considered joint. As compared to the solid finite element method, an important saving in computational cost is achieved.

Strength Prediction of Bonded T-Peel Joint with Single Overlap Support

Bonded structure are commonly three types, purely adhesive bonded, weld-bonded and adhesive/mechanical structures. Generally, peel and overlapped joints are commonly used in the development of bonded structures. T-Peel bonded joint has week tensile loading strength compare to double-overlap bonded joint. The present work aimed to predicting the strength of bonded T-peel joint with single overlap support using finite-element method. For comparison purposes, normal bonded T-peel joint is included in this study. It was found the introduction of a single overlap support for bonded T-peel joint strengthening the joint by 300%. Furthermore, it was reported that the proposed joint strength increased further with increase of the overlap support plate length and thickness.

Analysis of T-Peel Weld-Bonded Joint with Single Overlap Support

Bonded structure are commonly of three types, purely adhesive bonded, weld-bonded and adhesive/mechanical structures. Peel and overlapped joints are commonly used in the development of bonded structures. T-Peel bonded joint has week tensile strength load compared to double-overlap bonded joint. The present work aimed to predicting the strength of weld-bonded T-peel joint with single overlap weld-bond support plate using finite-element method. For comparison purposes, weld-bond T-peel joint without support is included in this study. It was found the peak stress is concentrated towards the inner far end of T-peel mid-layer of adhesive and through weld-nugget center. The introduction of single overlap weld-bond support for T-peel joint strengthen the joint by 500%.

Experimental and Numerical Analysis of T-peel Joints for the Automotive Industry

The T-peel joint is commonly used in the automotive industry, especially in the panels of the load compartment in vans. In order to determine the effect of using a structural adhesive instead of spot-welding, a detailed series of tests and finite element analyses were conducted. The adhesive was a toughened epoxy and the adherend was mild steel used in the manufacture of the car bodyshell. Various parameters were investigated such as the bondline thickness and adherend radius. The spew fillet was maintained flush in all cases. Contrary to the case of lap joints, there are no stress concentrations around the fillet area and, therefore, it is possible to use the maximum uniaxial tensile stress as a failure criterion for these joints. The bending moment at failure was found to be constant across the different geometries modelled, and it was also similar to that found in lap shear joints in previous studies.

Non-destructive evaluation of the adhesive fillet size in a T-peel joint using ultrasonic Lamb waves and a linear network for data discrimination : Bork, U.; Challis, R.E. Measurement Science and Technology, Vol. 6, No. 1, pp. 72–84 (Jan. 1995)

Non-destructive evaluation of the adhesive fillet size in a T-peel joint using ultrasonic Lamb waves and a linear network for data discrimination : Bork, U.; Challis, R.E. Measurement Science and Technology, Vol. 6, No. 1, pp. 72–84 (Jan. 1995)

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.

Static Strength and Fatigue Performance of Aluminium-Adhesive T-Peel Joints

Numerical predictions of the tensile stresses within adhesively-bonded aluminium T-peel joints have established where critical fatigue defects are likely to initiate and propagate to fracture. These predictions of maximum stress correlate directly with static strength measurements of such joints. The results presented within this article elucidate the region of cohesive crack initiation, its subsequent direction of propagation and the relative duration of the different stages of fatigue crack growth. Separate stages of embedded, surface and through-width fatigue growth of cohesive defects with a T-peel joint are identified and compared. In this manner the fatigue life of typical bonded aluminium-epoxy T-peel joints has been established from the first stages of crack initiation to final joint fracture. It has been shown that joint static and fatigue strengths are maximized by having a maximum amount of adhesive within the fillet region of the joint.

Fatigue Growth of Cohesive Defects in T-Peel Joints

Abstract This paper uses 2D and 3D finite element models to predict the stresses within bonded and weld-bonded T-peel joints. Epoxy adhesive is modelled as a homogeneous layer providing a perfect bond between aluminium adherends. Knowledge of the critical tensile stresses enables the likely region of fatigue crack initiation to be predicted. The long term reliability and durability of a joint depend directly on its fatigue strength. This research elucidates the region of cohesive crack initiation, the subsequent direction of crack propagation and the relative duration of the different stages of fatigue crack growth. The various stages of embedded, surface and through-width fatigue growth of cohesive defects within a T-peel joint are compared. This establishes fatigue life from crack initiation to final joint fracture for typical bonded and weld-bonded T-peel joints.

Development of cohesive fatigue cracks in T-peel joints

This paper uses two- and three-dimensional finite element models to predict the stresses within bonded and weld-bonded T-peel joints. Epoxy adhesive is modelled as a homogeneous layer providing a perfect bond between aluminium adherends. Knowledge of the critical tensile stresses enables the likely region of fatigue crack initiation to be predicted. The long-term reliability and durability of a joint depend directly on its fatigue life. This research elucidates the region of cohesive crack initiation, the subsequent direction of crack propagation and the relative duration of the different stages of fatigue crack growth. The various stages of embedded, surface and through-width fatigue growth of cohesive defects within a T-peel joint are compared. This establishes fatigue life from crack initiation to final joint fracture for typical bonded T-peel joints.