In the present research, the modulus of a double lap bonded joint in the strain rate ranges of 0 to 1055 S-1 is predicted by a theoretical model. In this approach, using geometrical parameters of bonded joint, elastic young modulus of adherends and shear modulus of the adhesive layer at two different strain rates, strain rate sharing of bonded joint’ constituents can be calculated. Also, using these data, shear modulus of the adhesive layer at its share of strain rate is calculated; Then, using these data, dynamic modulus of double lap bonded joint can be computed. Calculating stiffness of the double lap bonded joint using geometrical parameters of bonded joint and mechanical parameters of constituents without need to do the test is the advantage of this model. Also, in this manuscript, a finite element model (using Abaqus Explicit) is presented in order to predict dynamic modulus of double lap bonded joint using elastic mechanical properties of bonded joint constituents, their densities and bonded joint geometrical parameters. The two presented models show a similar trend in the prediction of double lap bonded joint’ modulus; in a way that, at the two models, bonded joint’ modulus is increased by increasing strain rate. The maximum difference between the two models is about nine percent.

In this paper, the strain energy release rate of first mode of failure in the adhesive bonding of two composite plates composed of unidirectional glass fiber is calculated using double cantilever beam specimen. Araldite 2011 adhesive connection which is widely used in the aerospace industry has been employed. Strain energy release rate is calculated by the modified beam method, compliance calibration method and modified compliance calibration method from experimental results. For modeling crack growth in adhesive bonding of two composite plates, the Extended Finite Element Method has been employed. Average value of critical strain energy release rate calculated by the modified compliance calibration method is considered as software input. After comparing force - displacement curve obtained from experimental data and numerical solution that represents good precision of the Extended Finite Element Method in calculating the maximum force and corresponding displacement and also linear part of force-displacement curve, strain energy release rate - force curve, stress intensity factor – force curve, strain energy release rate – displacement of the load effective point and failure stress - stress intensity factor curve are evaluated.

Compared to mechanical joining methods, adhesive bonded joints have uniform stress distribution, good fatigue performance and better weight reduction effect. Some failures in the adhesive bonded joints are caused by the presence of contamination and inappropriate roughness in the joint surfaces. In this study, the effect of different surface treatment on the mechanical behavior of the composite/aluminum adhesive joint in the mode I of fracture is investigated by using Double-cantilever beam specimen. Surface treatment has been done with three methods of Peel Ply Processing, Sanding and Laser for composite adherent and two methods of Sanding and Laser for aluminum adherent. In the laser surface treatment method, the transverse distance of the grooves and the spots diameter are fixed, and the scanning speed and power of the machine are variable. The surface roughness measurement of the adherents shows the increase of the surface roughness up to a certain value of the laser energy density, but after that the roughness has decreased due to the melting of the adherent surface. The results show an increase of 13.43% and 7.46% in the critical strain energy release rate of the mode I of fracture using the laser surface treatment method compared to the Sanding method and the Peel Ply Processing method, respectively. Also, examination of the fracture surface of the joint shows an increase in the failure mode of fiber tearing at the joint surface with the correct selection of laser parameters, which has improved the strength of the joint.

Due to the increasing need of composite materials to achieve desired properties and functions, the use of composite materials in the construction industry is significantly in a growing trend. In this study, it is tried to introduce the structure and variety of FRP composite materials and then to express about the behavior and mechanical properties of FRP composites and how to find these specifications using tensile testing. The important point in using these materials is their connections. It is tried to initially present about bolted and adhesive connection and then by 3 tests of beam to column connection, using bolted, enhanced bolted and adhesive connections, the performance of these connections have been checked. Innovation used in these study is applying enhanced bolted connection provided by beams and columns. By doing these tests can be seen in terms of strength parameters, the bearing capacity of enhanced bolted connection and adhesive joints is approximately equal and to double amount of corner bolted connection can bear the load. Considering initial stiffness of the frame, enhanced bolted and adhesive was about equal and their initial stiffness was five times more than corner bolted connection. In term of the rotational stiffness, adhesive joints that have the most rotational stiffness with 1.75 times more rather than enhanced bolted connection and 8 times of bolted connection. Adhesive joint has much better performance than bolted connection, but with very little shift rather than bolted connection, will be fragmented (brittle fracture). So in bolted connection, it should be used some enhancers to enhance the performance of mechanical performance and in adhesive joints, the adhesion between the fibers in the composite should be increased. One of the ways to increase adhesion between fibers in FRP composites is to use strong resins such as epoxy and also to monitor the proper curing of resins.

Application of the adhesive joint due to great advantages are increasing in many packaging industries. Knowing the effective parameters on the adhesive joints can led to better joint strength and therefore increase in the adhesive joint quality. In the current study, the theories on the adhesive joints have been expressed and then the stress variation along the joint area for different loading conditions and different failure modes will be discussed. Peel and cleavage are known as the key stresses in adhesive failure. To improve the adhesive strength these two stresses must be uniformed along the adhesive area. Two kind of failures are considered for adhesive joint. Adhesive failure mainly occurs due to the lake of strength of the adhesive material or improper cooking condition. Cohesive failure arises because of inappropriate surface preparation. To optimize the adhesive joints key factors in adhesive properties, adhesive area geometry and pre adhesive preparation are investigated.

Adhesive joints have been employing in engineering structures such as marine, aerospace, automotive, oil and gas industry. Since the joints are the weakest part of engineering structures, the fracture possibility in adhesive joint is high. Therefore, structural health monitoring of adhesive joint is an important issue. The aim of this paper was condition monitoring of damage in the single lap adhesive joint by multiwall carbon nanotubes. This work is carried out by recording the electrical resistance change during the mechanical loading. This damage propagation is observed as a crack extension in adhesive joint. Firstly, MWCNTs with 9 wt.% are dispersed in an epoxy resin by ultrasonic device. Then, the hardener is added to the nonoadhesive. The obtained material is immediately poured into single lap adhesive joint mold. The defective adhesive joints were manufactured with circular and square defects in different sizes i.e. 10%, 30% and 70% overlap area. The specimen is subjected to tensile test and electrical resistance change are recorded during the shear load. The results showed that the maximum value of relative resistance change is occurring in the adhesive joint comprises of square defect with 30% overlap area of defect. In this situation, the crack was propagated in nanoadhesive and a small part of a crack was extended from defect boundary.

In this paper، the influencing factors on hybrid adhesive-riveted joints were investigated. For this purpose، first a finite element model was validated based on experimental results، then the effects of influencing material and geometrical factors on the strength of the hybrid joints were studied using the explicit finite element analyses. The numerical model was able to simulate damage in the adhesive layer and in the rivets. The results showed that in a hybrid adhesive-riveted joint، it is better to position the rivets where a minimum reduction in the adhesive joint due to the rivet holes obtained i. e. as far as possible from the joint ends. This is in contrary to the riveted joints in which placing the rivets closer to the joint ends resulted higher joint strength. In general، incorporating rivets in an adhesive joint for manufacturing a hybrid joint can result higher or lower joint strength in comparison with the adhesive joint in different conditions that were studied in this research. It should be noted that in case that a low-strength adhesive is utilized in a hybrid adhesive-riveted joint then placing the rivets closer to the joint ends can results higher strength for the joint similar to the riveted joints.

In this article, failure and damage in second mode of adhesive composite joint was investigated according to the bending in endnotch flexure specimen. To create an adhesive joint between two composite plates made of unidirectional glass fiber, Araldite 2011 resin was used which is widely capable in manufacturing turbine blades and aerospace industries. At the first, failure of second mode fracture of adhesive joint mechanisms has experimentally investigated. Then with considering this result with strain energy release rate on mode II of fracture in specimen for Araldite 2011, 776.22 J/m2 was calculated. In the following calculating critical strain energy release rate on mode II by using experimental results, XFEM method used for modeling crack growing in adhesive joint by using Abaqus software. At the end the amount of mode II fracture toughness for Araldite 2011 is calculated from numerical method which is 40.53MPa√m.

Due to the need of some industries for the direct bonding of metal and composite layers to each other and its special applications in the industry, this paper examines the solution for adhesive bonding between steel and carbon-phenolic composite. Since this composite layer does not inherently have a good adhesion to the steel surface, steel substrate surface preparation is inevitable in order to create a resistant bonding. In this research, for the preparation of steel surfaces, the knurling process with four types of knurl wheels with different geometries and pitches was used and then, by applying the adhesion tensile test, the strength of adhesive bonding of the composite layer to their surface was investigated. The results showed that in about 50% of all samples, the knurling operation was able to increase the adhesive bond strength compared to the sample with smooth metal surface. In Comparison of adhesive bond strength for two cross and straight knurl patterns, the tensile bond strength created by straight knurl shape was reported about 5 times greater than the cross knurl shape in the case of equal tensile and at pitch equal 0.6 mm. Also, the highest value for adhesive bond strength was reported in 12.62 MPa for preparated surface by using of straight knurl shape at pitch equal 0.6 mm which increased by 76% compared to machined smooth surface.

One of the causes of failure of adhesive joints is the stress singularity that often occurs at the free edge of the bond end. Geometric model change at the joint end can be used to reduce the stress concentration at this location. In this study, a new design called "arc adhesive model" is suggested for adhesively bonded joint of the cap of a rotational composite tank; and is compared with two conventional geometrical models including baseline model, and concave end model. Regarding to importance of transverse shear stress and normal peeling stress in examination of bonding strength, the stresses at the free end of bond are investigated using numerical analysis for all three models. Also, effect of tank rotation frequency on the stress components is investigated. Results show that the arc adhesive model can cause a significant decrease in transverse shear stress and peeling stress in adhesive joint of the cap.