Papers by Keyword: Adhesive Bonding

Abstract: The aim of this paper is to investigate the effect of bending on the actual stress distribution of a cantilevered single-lap adhesive joint under tension using the 3D FEA method. Five layers of elements were used across the adhesive thickness in order to obtain an accurate indication of the variation of stresses. All the numerical results obtained from the FEA show that the spatial distribution of all components of stress are similar for different interfaces though the stress values are obviously different. The results also show that the maximum value of the stress component S33 is higher than the maximum value of the stress component S11 which would have been expected to be the most dominant since the joint is subjected to tensile loading. The reason for this behaviour is the effect of bending at the bonded section of the joint.

Abstract: Adhesive bonding is a high-speed fastening method which is suitable for joining advanced lightweight sheet materials that are hard to weld. Latest literature relating to finite element analysis (FEA) of fatigue behaviour of adhesively bonded joints is reviewed in this paper. The recent development in FEA of fatigue behaviour of adhesively bonded joints is described with particular reference to three major factors that influence the fatigue behaviour of adhesively bonded joints: failure mechanism, environmental effects and hybrid joining techniques. The main FE methods used in FEA of fatigue behaviour of adhesively bonded joints are discussed and illustrated with brief case studies from the literature.

Abstract: Based on 3D elastic-plastic finite element method (FEM), the geometry size effect on strength in aluminum alloy adhesive joints is presented in this paper. The numerical and experimental results show that with the adhesive thickness increased, the adhesive joint strength first increases then decreases, and in a certain range, with the adhesive thickness increased, the adhesive joint strength is nonlinear to the overlap length but linear to the overlap area. In the case of the same overlap area, the adhesive joint strength can be increased by increasing overlap length and decreasing overlap width.

Abstract: Adhesive bonding is a high-speed fastening technique which is suitable for joining advanced lightweight sheet materials that are dissimilar, coated and hard to weld. Major advances have been made in recent years in adhesive bonding technique. Latest literature relating to finite element analysis (FEA) of adhesively bonded single-lap joints (SLJs) is reviewed in this paper. The recent development in FEA of SLJs is described with particular reference to three major factors that influence the success of adhesive bonding technique: failure mechanism, environmental effects and mechanical behavior. The main FE methods used in FEA of SLJs are discussed and illustrated with brief case studies from the literature. Areas where further useful progress can be made are also identified.

Abstract: The present work involves a numerical modelling of the Embedded Process Zone (EPZ) by utilizing the elastoplastic Mode I and Mode II fracture models for the simulation of plastically deforming adhesive joints. A traction-separation law was developed separately for Mode I and Mode II. For the analysis of the mixed-mode fracture processes, the cohesive zones in Mode I and Mode II fracture were assumed uncoupled. The experimental programme involved the fabrication and testing of Double Strap Joints (DSJs) and Single Lap Joints (SLJs). By fitting the numerical results to the experimental ones, the basic cohesive parameters of the problem were defined.

Abstract: With increasing application of adhesive bonding structures, the quality assessment of adhesive bonding became critical. Ultrasonic approach was an acknowledged promising method in many Nondestructive testing (NDT) techniques. The research object was to use analytical models to develop a quantitative understanding of the affections in different situations on the dispersion properties. An improved global matrix method was introduced to compute the dispersive curves, which can effectively eliminate the instability for thicker layers and higher frequencies. In order to evaluate the disbond defect, the cohesive strength degradation mode and the spring mode were then adopted to describe the cohesive failure and the interface failure, respectively. In the paper, cohesive failure, interface failure and mixed failure were analyzed for the steel/adhesive layer/insulation layered structure. Interface failure induced the modes of multilayer structure to regress to the modes of single layers, while the cohesive failure made the dispersive curves move to the lower frequency direction, and changing the relative position of spring layer led the dispersive curves shift to the higher frequency direction. Among all the factors, the interface failure was dominant. Finally, the variety of the dispersive modes in a special frequency band (1~1.5MHz) was found that can be regarded as parameters of the adhesive bonding quality.

Abstract: This paper presents a method to fabricate the microfluidic devices with insulated electrodes on top and bottom sides of the channel. To form the channel containing vertically opposing electrodes, two processed substrates were bonded together with an SU-8 intermediate layer sandwiched in between. An adhesive bonding technique, at wafer level, with accurate alignment was developed. Instead of using wafer bonder, the bonding was conducted on a hotplate, which relieves the requirement on the process equipment to a great extent.

Abstract: An excellent pressure sensor based a simple fabrication technology is presented. Differently from the present prevailing fabrication process of silicon piezoresistive pressure sensor: platinum is used as the sensing material, with a smaller but acceptable sensitivity and much simpler processes; adhesive bonding with SU-8 is used as an alternative choice to anodic bonding, and we choose a vacuum hot plate to avoid using a bonding machine. To achieve a successful bonding, it is found that pre-bake time and pumping time are the most important factors. Bonding quality is evaluated by inspection through the glass with 95% of the area successfully bonded and the failed area in the edge of the wafers. The measured bonding strength is 17.34 MPa. The Pressure-Voltage characteristic test results display a good linearity within 0.2% and especially a good precision within 0.035% in square fitting. The temperature drifting is also tested and the TCO is 1250 ppm/(°C FSO). The long-term stability of the sensor at a constant pressure is a fluctuation within 40 Pa (0.098% FSO) in 7 days. Both the simple fabrication process and the excellent performance of the sensor suggest that this sensor is a much good choice in measuring atmospheric pressure.

Abstract: Failure strength evaluation on resistance welding mixed adhesive bonding was studied. Tensile-shear tests were carried out with the single-lap specimen, using both resistance welding and adhesive bonding. Peel tests were also carried out with DCB specimen. Composites were manufactured using the polyester as a matrix and bamboo natural fiber layer as a reinforcement. Adhesive bond, having bonding strength that remains unaffected by heat at resistance welding, were selected. Generally, adhesive bond require a long curing time and have little strength before hardening. Resistance welding helps weakness of adhesive bond both curing time and peel strength. And the spew fillet of adhesive bonding also helps to release stress intensity of edge of joining. The failure mechanism was discussed in order to explain higher peel and tensile-shear strength of resistance welding mixed adhesive bonding.

Abstract: The failure in an adhesive-bonded structure starts at the interface, and the interfacial fracture is of interest whenever adhesion between different materials is concerned. One of primary factors limiting the application of adhesive-bonded joints to structural design is the lack of a good evaluation tool for adhesion strength to predict the load-bearing capacity of boned joints. The adhesion strength of composite/steel bonding has been evaluated using interfacial fracture mechanics characterization. The energy release rate of a composite/steel interfacial crack was compared with the fracture toughness of the interface, which was measured from bi-material end notched flexure (ENF) specimens, to predict the failure loads of bi-material lap joints. Fracture toughness, IIc G , was regarded as a property of the interface rather than a property of the adhesive. The results show that interfacial fracture mechanics characterization of adhesion strength can be a practical engineering tool for predicting the load-bearing capacities of adhesive-bonded joints.