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Adhesively bonded joints are used in many fields, especially in the automotive, marine, aviation, defense and outdoor industries. Adhesive bonding offers advantages over traditional mechanical methods, including the ability to join diverse materials, even load distribution and efficient thermal-electrical insulation. This study aims to investigate the mechanical properties of adhesively bonded joints, focusing on adherends produced with auxetic and flat surfaces adhered with varying adhesive thicknesses.

The research uses three-dimensional (3D)-printed materials, polyethylene terephthalate glycol and polylactic acid, and two adhesive types with ductile and brittle properties for single lap joints, analyzing their mechanical performance through tensile testing. The adhesion region of one of these adherends was formed with a flat surface and the other with an auxetic surface. Adhesively bonded joints were produced with 0.2, 0.3 and 0.4 mm bonding thickness.

Results reveal that auxetic adherends exhibit higher strength compared to flat surfaces. Interestingly, the strength of ductile adhesives in auxetic bonded joints increases with adhesive thickness, while brittle adhesive strength decreases with thicker auxetic bonds. Moreover, the auxetic structure displays reduced elongation under comparable force.

The findings emphasize the intricate interplay between adhesive type, bonded surface configuration of adherend and bonding thickness, crucial for understanding the mechanical behavior of adhesively bonded joints in the context of 3D-printed materials.

Fibre reinforced polymer composites (FRPs) are finding increasing usage in many industrial sectors. Adhesive bonding is often the most attractive joining technique for these materials in terms of structural efficiency and cost of manufacture. However, concerns regarding the lack of reliable design methods, the long term ageing behaviour and the difficulties in non‐destructive evaluation and repair of bonded joints has led to a reluctance to use adhesives in primary structures. DERA has been involved in the assessment of adhesive bonding for joining FRPs for many years. This paper focuses on investigations at DERA into the effects that environment and fatigue loading have on the performance of bonded composite joints, and briefly reviews current approaches to strength and lifetime prediction. It is seen that adhesively bonded composite joints can be significantly affected by the service environment, however, this is highly dependent on the joint type and materials involved.

Adhesively bonded joints are gaining importance in the structural joining processes competing against welding and bolting processes. However, long-term behaviour of adhesively bonded joints is still an open question. Due to the increasing interest in adhesively bonded joints, mainly in the transports industry, there is a need to deep the knowledge about the fatigue behaviour of adhesive joints with metallic substrates allowing the development of reliable joints to resist cyclic loadings. The paper aims to discuss these issues.

An experimental research aiming at characterizing the fatigue behaviour of adhesively bonded aluminium substrates is presented in this paper, covering both fatigue crack propagation and global S-N behaviours. Double cantilever beam (DCB), end notch flexure (ENF) and double lap joints (DLJ) specimens built using the AA6061T651 substrate and epoxy adhesive were used to evaluate the pure modes I and II fatigue crack propagation rates and the S-N fatigue behaviours.

DCB and ENF specimens allowed the formulation of pure modes I and II fatigue crack propagation laws including the propagation thresholds. DLJs showed higher static shear strength than recommended by the manufacturer for aluminium substrates, but fatigue resistance of the DLJs was lower than suggested by the manufacturer. The fatigue damage process in the DLJs was dominated by a fatigue crack initiation process.

A consistent fatigue research on adhesively bonded aluminium substrates is presented covering in the same study aspects of fatigue crack propagation and fatigue crack initiation. Data reduction schemes involving both numerical and analytical procedures were followed. Proposed work constitutes a rigorous basis for future fatigue prediction models developments.

Due to its inexpensive production costs, low stress concentration and maintenance-friendliness, the adhesive bonded pipe joint is frequently utilized for pipe connection. However, further theoretical analysis is needed to understand the debonding failure mechanism of such bonded pipe joints under axial tension.

In this study, based on the bi-linear cohesive zone model, the integrated closed-form solutions were derived by considering the axial stiffness ratio and failure stage to determine the relative interfacial slip, interfacial shear stress and relationship of tension–displacement in the bonded pipe joint.

Additionally, solutions for the critical bonded length and the ultimate load capacity were put forth. Besides, the numerical study was conducted to verify the theoretical solutions regarding the load–displacement relationship. The interfacial shear stress distribution at different failure stages was presented to understand the interfacial shear stress transmission and debonding process. The effect of bonded length on the ultimate load and ductility of pipe joints was also discussed.

The findings in this study can give a reference for the design of bonded pipe joints in their actual engineering applications.

The purpose of this paper is to evaluate and exploit the combination of additive manufacturing polymeric technology and structural adhesives. The main advantage is to expand the maximum dimension of the 3D printed parts, which is typically limited, by joining the parts with structural adhesive, without losing strength and stiffness and keeping the major asset of polymeric 3 D printing: freedom of shape of the system and low cost of parts.

The materials used in the paper are the following. The adhesive considered is a commercial inexpensive acrylic, quite similar to superglue, applicable with almost no surface preparation and fast curing, as time constraint is one of the key problems that affects industrial adhesive applications. The 3D printed parts were in acrylonitrile butadiene styrene (ABS), obtained with a Fortus 250mc FDM machine, from Stratasys. The work first compares flat overlap joint with joints designed to permit mechanical interlocking of the adherends and then to a monolithic component with the same geometry. Single lap, joggle lap and double lap joints are the configurations experimentally characterized following a design of experiment approach.

The results show a failure in the substrate, due to the low strength of the polymeric adherends for the first batch of typical bonded configurations, single lap, joggle lap and double lap. The central bonded area, with an increased global thickness, never does fail, and the adhesive is able to transfer the load both with and without mechanical interlocking. An additional set of scarf joints was also tested to promote adhesive failure as well as to retrieve the adhesive strength in this application. The results shows that bonding of polymeric AM parts is able to express its full potential compared with a monolithic solution even though the joint fails prematurely in the adherend due to the bending stresses and the notches present in the lap joints.

Because of the 3D printed polymeric material adopted, the results may be generalized only when the elastic properties of the adherends and of the adhesive are similar, so it is not possible to extend the findings of the work to metallic additive manufactured components.

The paper shows that the adhesives are feasible way to expand the potentiality of 3 D printed equipment to obtain larger parts with equivalent mechanical properties. The paper also shows that the scarf joint, which fails in the adhesive first, can be used to extract information about the adhesive strength, useful for the designers which have to combine adhesive and additive manufactured polymeric parts.

To the best of the researchers’ knowledge, there are scarce quantitative information in technical literature about the performance of additive manufactured parts in combination with structural adhesives and this work provides an insight on this interesting subject. This manuscript provides a feasible way of using rapid prototyping techniques in combination with adhesive bonding to fully exploit the additive manufacturing capability and to create large and cost-effective 3 D printed parts.

The aim of the paper is to study the feasibility of direct ultrasonic bonding between contact pad arrays on flexible printed circuit boards (FPCB) and rigid printed circuit boards (RPCB) at ambient temperature.

Metallization layers on the RPCB comprised Sn on Cu while the pads on the FPCB consisted of Au/Ni/Cu. Prepared RPCB and FPCB were bonded by ultrasound at ambient temperature using an ultrasonic frequency of 20 kHz, a power of 1,400 W, and 0.62 MPa of bonding pressure. The bonded samples were cross‐sectioned and the joints and microstructures were observed by Field Emission Scanning Electron Microscopy (FE‐SEM) and Energy Dispersive Spectroscopy (EDS). The soundness of the joints was evaluated by pull testing.

Robust bonding between FPCB and RPCB was obtained by bonding for 1.0 and 1.5 s. This result has confirmed that direct room temperature ultrasonic bonding of Au and Sn is feasible. At a longer bonding time of 3.0 s, cracks and voids were found in the joints due to excessive ultrasonic energy. The IMC (intermetallic compound) between the Sn layer and pads of the RPCB was confirmed as Cu₆Sn₅. On the FPCB side, Cu₆Sn₅ and Ni₃Sn₄ were formed by contact with the facing Sn coating, and mechanically alloyed Cu_0.81Ni_0.19 was found within the pads. Meanwhile, the strength of bonded joints between FPCB and RPCB increased with bonding time up to 1.5 s and the maximum value reached 12.48 N. At 3.0 s bonding time, the strength decreased drastically, and showed 5.75 N. Footprints from the fracture surfaces showed that bonding started from the edges of the metal pads, and extended to the pad centers as ultrasonic bonding time was increased.

Direct ultrasonic bonding with transverse vibration at ambient temperature between the surface layers of the pads of FPCB and RPCB has been confirmed to be feasible.

Contact problems are among the most difficult ones in mechanics. Due to its practical importance, the problem has been receiving extensive research work over the years. The finite element method has been widely used to solve contact problems with various grades of complexity. Great progress has been made on both theoretical studies and engineering applications. This paper reviews some of the main developments in contact theories and finite element solution techniques for static contact problems. Classical and variational formulations of the problem are first given and then finite element solution techniques are reviewed. Available constraint methods, friction laws and contact searching algorithms are also briefly described. At the end of the paper, a bibliography is included, listing about seven hundred papers which are related to static contact problems and have been published in various journals and conference proceedings from 1976.

This paper aims to study the benefits of use of bi-adhesive (combination of two different adhesives) over conventional single adhesive in bonded lap joints. Characterise damage severity due to cohesive and adherent failure as feedback for operating load levels that assist in developing damage tolerance design of the adhesively bonded joints.

Single lap joint where the adherent plate is made up of aluminium alloy joined together with bi-adhesives is analysed. The nature of adhesives ranges from brittle, elastic-plastic, moderately ductile to largely ductile. Numerical analysis is performed considering the material and geometric non-linear behaviour of the joint. The optimum bond ratio of bi-adhesives and the effect of the location of adhesive on the stress distribution are studied. The cohesive zone modelling (CZM) is adopted to account for the cohesive failure of the joint. The adherent plate failure is also addressed by modelling and studying the behaviour of the crack at different locations in the plate using modified virtual crack closure integral (MVCCI).

The results obtained from the stress analysis show some important characteristic behaviour of the bi-adhesive joint. Although bi-adhesive is expected to result in improved joint strength, the purpose gets defeated if a brittle adhesive is used at the corners and ductile adhesive at the middle. The joint strength based on CZM, evaluated for a single adhesive, is in good comparison with the experimental results from the literature. Also, the location of the crack in the adherent plate plays a significant role in the failure of the joint.

Estimating joint strength for the bi-adhesive model using CZM and evaluating damage severity in the presence of de-bond and crack in the bi-adhesive lap joint model assists in developing robust damage tolerance design models of such joints.

This paper aims to present the classification, representation and extraction of adhesively bonded assembly features (ABAFs) from the computer-aided design (CAD) model.

The ABAFs are represented as a set of faces with a characteristic arrangement among the faces among parts in proximity suitable for adhesive bonding. The characteristics combination of the faying surfaces and their topological relationships help in classification of ABAFs. The ABAFs are classified into elementary and compound types based on the number of assembly features exist at the joint location.

A set of algorithms is developed to extract and identify the ABAFs from CAD model. Typical automotive and aerospace CAD assembly models have been used to illustrate and validate the proposed approach.

New classification and extraction methods for ABAFs are proposed, which are useful for variant design.

The purpose of this study is to investigate the effect of chip and substrate thickness on the thermal cycling reliability of flip chip joints assembled with anisotropic conductive adhesives (ACA) on FR‐4 substrates.

Four test lots were assembled with two substrates and two test chips. The thicknesses of the substrates were 710 and 100 μm and the thicknesses of the chips were 480 and 80 μm. To study the effect of the bonding pressure each test lot contained four test series bonded with four different bonding pressures. The reliability of the test samples was studied using a temperature cycling test.

The reliability of the test lots varied widely during the test. The test lot with a thin substrate and thin chip demonstrated considerably better reliability than the other test lots. In addition, the test lots had different failure mechanisms. After the test delamination was found in every test lot except the one assembled with the thin chip and the thin substrate.

The work shows that the thermal cycling reliability of ACA flip chip joints can be markedly increased by using thinned chips or reducing the thickness of the substrate.