Sharif Digital Repository

In this paper, several numerical simulations are performed to study the failure of epoxy adhesive joining composite plates. Different geometries for the joint and its edge are considered, and the effects of these geometries on the failure load are investigated. Moreover, the joints are subjected to different types of loading in order to determine the failure load. The failure theories of composite materials are implemented into the finite element software ABAQUS, and the failure propagation in the joint is studied. © 2020, Shiraz University  

The aim of this research is to optimize the geometry of the overlap in mixed adhesive single-and double-lap joints using a modified version of Bees and Genetic Algorithms (BA and GA). Accounting for adherends Poisson's ratio in the deduced equilibrium equations, the proposed shear lag model gives a more accurate approximation of joint failure load in comparison with Volkersen's solution. The objective functions used in this work are used separately to maximize the load bearing capacity f and the specific strength (f/w) of the joint. This procedure is applied to optimize aeronautical adhesively bonded assemblies, while taking manufacturing constraints into account. The employed constraints... 

Three-dimensional thermo-mechanical stress analysis of composite joints with bi-adhesive bonding is presented using the full layerwise theory. Based on three-dimensional elasticity theory, sets of fully coupled governing differential equations are derived using the principle of minimum total potential energy and are simultaneously solved using the state space approach. Results show that bi-adhesive bonding substantially relieves the edge effects. Moreover, series of parametric studies reveal the nonlinear effects of bonding length ratio and the relative stiffness and coefficient of thermal expansion of the mid- and side-adhesives. It is also concluded that the optimum design of a bi-adhesive... 

Space environments have a significant influence on advanced composite structures and adhesive joints. Degradation in the mechanical properties of aerospace materials changes the dynamic behavior of the structures and adhesive joints. In this paper, a typical tubular adhesive joint with material degradation due to geostationary orbit (GEO) thermal cycles has been studied numerically with Python scripts. Adhesive joint geometry and boundary conditions are the main parametric study parameters. The results show that the first non–zero natural frequencies of the clamped-free tubular adhesive joint decreased due to mechanical property degradation. A dynamic behavior comparison of the degradation... 

The creep behaviour of adhesively bonded joints is one of the major concerns in modern industry due to their application at relatively high temperature. In this re-search, the effect of added RGO on the creep behaviour of the Araldite 2011 adhesive is investigated. Uni-axial creep tests have been carried out on neat Araldite 2011 and RGO added adhesive at different stress and temperature levels. It has been shown that adhesive with RGO particles demonstrate higher creep resistance. Also, general time hardening models are developed for both materials and their constitutive coefficients have been determined using creep test data. Based on these models, the creep behavior of single lap joints... 

This study investigated the mode I fracture behavior of double cantilever beam (DCB) epoxy adhesive joints with similar adherends on the both sides (i.e., aluminum-aluminum or copper-copper) at different strain rates; i.e., quasi-static (∼10−3 s−1), low (∼7 s−1) and intermediate (∼14 s−1) rates. The fracture energy of the DCB joint in Al-adhesive-Al specimens decreased (i.e., by ∼62%, p = 0.0013) with an increase in the applied strain rate from quasi-static to low values, while it remained almost unchanged with further increase of stain rate to intermediate range (p > 0.05). For Cu-adhesive-Cu cases, however, the fracture energy was found to be almost insensitive to the applied strain rate... 

This paper deals with analytical thermomechanical stress analysis of adhesively bonded composite joints in presence of a structural imperfection in the form of an interfacial void within the adhesive layer based on the full layerwise theory (FLWT). The joints are subjected to mechanical tension, uniform temperature change, or steady-state heat conduction. The proposed adhesive joint is divided into three distinct regions along its length and a large number of mathematical plies through its thickness. Three sets of fully coupled governing equilibrium equations are derived employing the principle of minimum total potential energy. The three-dimensional nonlinear interlaminar stress... 

In this research, Araldite 2011 has been reinforced using different weight fractions of Reduced Graphene Oxide (RGO). Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analyses were conducted and it has been shown that introduction of the RGO greatly changes the film morphology of the neat adhesive. Uni-axial tests were carried out to obtain the mechanical characteristics of the adhesive-RGO composites. It has been observed that introducing 0.5 wt% RGO enhances the ultimate tensile strength of the composites by 30%. In addition, single lap joints using neat adhesive and adhesive-RGO composites were fabricated to... 

Hybrid weld-adhesive bonding (AB) was used as an approach to improve the mechanical properties of martensitic stainless steel resistance spot welds. The weld fusion zone in both techniques was composed of predominantly martensite and δ-ferrite. It was found that the presence of adhesive does not induce excess hardening effect in the fusion zone. It was shown that hybrid AB/resistance spot welding) i.e. weld-bonding) technique can double the peak load and energy absorption of the joints compared to those of the resistance spot welds. To obtain high performance weld-bonded joints, heat generation during welding should be controlled to produce weld bonds with large fusion zone size, but without...