In this research, the transient SHEAR stress distribution in an adhesive joint due to fiber breakage has been investigated. Transient stress is a dynamic response of the joint to the fiber discontinuities till their static equilibrium state. To study this behavior, equations governing the motion of fibers in the matrix, due to their breakage, are derived and the effect of number of broken fibers is studied on transient response of the structure. SHEAR lag model is used to extract fiber displacement. The equilibrium equations are solved using the explicit finite difference method. The effect of fiber materials and adhesive thickness is also studied on stress distribution. Results show that for an increase in the number of broken fibers, the stress concentration in the composite structure increases. Moreover, the SHEAR stress created in the matrix and the adhesive layer is reduced with an increase in fiber elastic modulus, such that for glass and graphite fibers (E=74 and 130 GPa respectively), the maximum SHEAR stresses in the adhesive are 0.861 and 0.461 MPa, while in the adherends, they are equal to 3.192 and 2.409 MPa respectively.

In this study, the strengthening of cross-laminated timber (CLT) with glass fiber reinforced polymer (GFRP) on the lateral resistance (LR) of the SINGLE SHEAR LAP joints was investigated. Poplar (Populus alba) layers were used to construct the three-layer CLT. In first step, the effect of GFRP strengthening of CLT panel with three layers of FRP fastened with a lag screw, concrete screw, wood screw, and steel nail at an end distance of 1 cm on the lateral load capacity was investigated. In second step, the effect of the number of GFRP layers on the LR of the joint assembled with the lag screw with an end distance of 1 cm was investigated. Finally, the main effects of panel strength directions (major and minor axes), fastener types (lag screw, concrete screw, wood screw, and steel nail), and end distances (1and 2 cm) and their interaction on LR were investigated. The results showed that LR was increased by 22 to 53% with reinforcement, which was more considerable in joints with smaller diameter fasteners. By increasing the number of GFRP layers from one to three layers, LR was increased by 27%. By increasing the end distance, changing the fastener types and panel directions, LR was changed 114.7%, 219.6%, and 7%, respectively. The interaction of variables on LR showed that by simultaneously changing the fastener types × end distance, LR changed about 447%, which implied the importance of choosing the proper fastener with sufficient end distance to construct the joints with a metal connector such as brackets.

Polymer-based adhesives undergo creep deformation under constant loading due to their viscoelastic nature. The aim of this study was investigation of the effects of temperature level and stress-to-strength ratio on creep behavior of SINGLE LAP joints (SLJs) manufactured with adhesive Araldite 2011. Static tensile tests were done on the samples at 40 and 50° C. Then, the tensile creep tests were done at 40 and 50° C and at stress-to-strength ratios of 0. 25 and 0. 35. With increasing the stress-to-strength ratio from 0. 25 to 0. 35 at 40° C, the creep displacement and the slope of the second creep stage were increased by 24% and 96. 7%, while at 50° C such increase reached to 14. 3% and 79. 9%, respectively. With increasing the temperature from 40 to 50° C, at the stress-to-strength ratio of 0. 25, the creep displacement was increased by 20. 6% and the slope of second creep stage increased by 49. 5%. Whereas, at the stress-to-strength ratio of 0. 35, changing the temperature from 40 to 50° C resulted an increase in the creep displacement by 11. 1% and the slope of second creep stage by 36. 6%.

Constant loading causes creep deformation in polymer-based adhesives due to their visco-elastic nature. The aim of this study was Investigating the effect of 2-D defects on tensile and creep behavior of SINGLE-LAP ceramic-metal joints (SLJs) manufactured with adhesive Aqua-Flex. Static tensile test was performed at three ambient temperatures, 40°, C and 60°, C for flawless and defected adhesive joints in ceramics as well as defects in ceramics and aluminum, and then by applying final stress-to-strength ratios equal to 0. 40 and 0. 60, tensile creep test has been also performed. By increasing the final stress-to-strength ratio from 0. 40 to 0. 60 at ambient temperature, the creep displacement for flawless connection is 36%, this amount increases to 33% for defected ceramics and to 40% for ceramics with more defections. At 40°, C and 60°, C, respectively, this increase is 35% and 18% for defected connection, 54% and 5% for defected connection in ceramic and 39% and 42% for connection with defected connection in ceramic and aluminum. Also, as the temperature increases from ambient temperature to 60°, C, the breaking force for the three types of connections is reduced by 46%, 25% and 80%.

Reinforced concrete SHEAR walls have a wide range of applications as one of the main lateral load-bearing elements in the construction industry. Implementation constraints often require the use of longitudinal rebar LAP-spliced. The presence of rebar LAP-spliced allows for longitudinal rebar slippage in the connection zone, which, if it occurs, leads to a reduction in ductility and undesirable seismic performance of the wall. To further investigate this issue, after validating the numerical results with obtained previous laboratory experiments, the behavior of 24 wall models with different longitudinal rebar diameters, LAP-spliced lengths, percentage of longitudinal rebar, and rebar debonding were studied numerically and using finite element analysis. The selected models, considering bond strength and slippage at the connection zone, were examined under gravity and cyclic lateral loading using numerical and finite element methods. By comparing the obtained results, including hysteretic curves, ductility, energy dissipation, rebar strain, and crack propagation, with walls using continuous rebar, it was demonstrated that the presence of LAP-spliced in the wall causes rebar slippage in the connection zone. Additionally, in walls with 18mm and 20mm rebars diameter, ductility was reduced by approximately 2 times. The results indicated that the ductility of walls with LAP-spliced can be increased by up to 50% using debonding methods.

In aeronautical and automotive industries the use of rivets for applications requiring several joining points is now very common. In spite of a very simple shape, a riveted junction has many contact surfaces and stress concentrations that make the local stiffness very difficult to be calculated. To overcome this difficulty, commonly finite element models with very dense meshes are performed for SINGLE joint analysis because the accuracy is crucial for a correct structural analysis. Anyhow, when several riveted joints are present, the simulation becomes computationally too heavy and usually significant restrictions to joint modelling are introduced, sacrificing the accuracy of local stiffness evaluation. In this paper, we tested the accuracy of a rivet finite element presented in previous works by the authors. The structural behaviour of a LAP joint specimen with a rivet joining is simulated numerically and compared to experimental measurements. The Rivet Element, based on a closed-form solution of a reference theoretical model of the rivet joint, simulates local and overall stiffness of the junction combining high accuracy with low degrees of freedom contribution. In this paper the Rivet Element performances are compared to that of a FE non-linear model of the rivet, built with solid elements and dense mesh, and to experimental data. The promising results reported allow to consider the Rivet Element able to simulate, with a great accuracy, actual structures with several rivet connections.

Fatigue is one of the most important failure sources of material that is caused by repeatedly applied loads. It is a progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The experimental results of fatigue tests on Al-alloy 2024-T3 in double SHEAR LAP joints were used to estimate (model) fatigue life with artificial neural networks (ANN). Artificial neural networks with experimental data processing can find the knowledge or law lies behind the data, and unlike mathematical models, itas not necessary to determine the mathematical relation between inputs and outputs. To model by artificial neural network, one of the experimental data of fatigue life randomly selected for validation and two other were selected for testing, the rest of the data were used to find the optimal values of weights and bias. After being ensured of the model accuracy, it was used to predict the fatigue life at different loads in the working phase that had not been tested. Comparison of experimental results and the results of the model shows that a 3-layer artificial neural network with less than 10% error could be used to predict the fatigue life at different loads.

Adhesive joints find numerous applications in various industrial fields. They represent a valid alternative to traditional joining methods. Much of the available scientific literature has focused on the study of adhesive joints subjected to tensile loads. There have also been numerous studies concerning the stresses distributions in the adhesive layer. However, in real case applications, adhesive joints could also be subject to cyclic tensile-compression loads and therefore could be subject to buckling phenomena. The objective  of  the  present  paper  is  to  investigate  the  numerical  study  of  the  stress  distribution  in  the adhesive layer under buckling condition. The study presented develops with the analysis of a SINGLE-LAP joint  with  a  combination  of  steel  adherends  and  three  different  structural  adhesives  with  different thickness  and  Young’s  modulus.  The  joints  are  modeled  using  FE  ANSYS©19  software.  Through numerical  analyzes,  it  is  possible  to  predict  the  value  of  the  critical  load  for  each  SINGLE  analyzed combination. Once the critical load is determined, the stresses in the middle plane of the adhesive layer are determined. The results obtained show that for small adhesive thicknesses (i.e. 0.30 mm) it is possible to reduce the stress peaks - with the same critical load value - by using structural adhesives with low elastic modulus (e.g. silicones).

Adhesive joints are becoming increasingly popular in various industrial sectors. However, in spite of numerous recent studies in literature, the design phase of the adhesive joint is still challenging. The main issue in the design phase is the determination of the stress distribution in the adhesive layer under external mechanical loads. In the present study, a classical adhesive joint is analysed in comparison to its modified geometric configuration (i.e. tapered) aimed at reducing the magnitude of stress peaks. In particular, a SINGLE-LAP joint with steel adherends bonded with a commercial epoxy adhesive is analysed. A 3D FE analysis is conducted to determine the distribution of normal and SHEAR stresses in the mid-plane of the adhesive layer. The results obtained from the present study show that the inclusion of a small taper angle (i.e. 5°) leads to a remarkable reduction of normal stresses (up to 30%) compared to the classical configuration. It is observed that the further increase of the taper angle (up to 15°) does not lead to significant reductions of the stress peaks. The trend in SHEAR stresses, on the other hand, is in contrast: an increase in the taper angle leads to an increase in the SHEAR peaks. The method of tapering the adherends is effective in reducing the normal stresses, which are responsible for triggering the failure in the adhesive joint.

A novel semi analytical method is developed for transient analysis of SINGLE-LAP adhesive joints with laminated composite adherends subjected to dynamical loads. The presented approach has the capability of choosing arbitrary loadings and boundary conditions. In this model, adherends are assumed to be orthotropic plates that pursuant to the classical lamination theory. Stacking sequences can be either symmetric or asymmetric. The adhesive layer is homogenous and isotropic material and modelled as continuously distributed normal and SHEAR springs. By applying constitutive, kinematics, and equations of motions, sets of governing differential equations for each inside and outside of overLAP zones are acquired. By solving these equations, the time dependent SHEAR and peel stresses in adhesive layer as well as deflections, stress resultants, and moment resultants in the adherends are computed. The developed results are successfully compared with the experimental research presented in available literates. It is observed that the time variations of adhesive peel and SHEAR stress diagrams are asymmetric for the case of symmetric applied load with high variation rate. Moreover, it is reported that although the magnitude of applied transverse SHEAR force is reduced to 10% of applied axial force, however a significant increase of 40% in the maximum peel stress attained.