Laser Surface Microtexturing for Enhanced Adhesive Bonding in Steel–Polymer and Steel–Ceramic Joints

Channel Cracking and Interfacial Delamination of Indium Tin Oxide (ITO) Nano-Sized Films on Polyethylene Terephthalate (PET) Substrates: Experiments and Modeling

This paper introduces a novel approach to increasing the loading ability of adhesive joints by adding adhesively filled columns. Following procedures are taken for making adhesive joints with adhesively filled columns: At first, holes are drilled at the overlap region of adherends, and then these holes are filled with adhesive or reinforced columns (such as reinforced fiber composite, metal columns, etc.). At the same time, adhesive is also applied on the surfaces of the overlap of adherends. After cured, the reinforced columns and adhesive in the holes form so-called adhesively filled columns. In this study, strengths of single-lap adhesive joints with adhesively filled columns were measured experimentally. Stress and strain distributions at typical positions in adhesive layer were analyzed by using Finite Element Method (FEM). Failure mechanics of the joint were analyzed. It was found that to well-bonded joints, the metal columns make the joint strength increase obviously and the joint strength increases with increasing of adherend thickness. Therefore, using reinforced columns in adhesive joints is an effective approach to generalizing adhesive joints from thin-walled joints to loading sizable bulk ones.

The main purpose of this paper was to determine the effect of biochemical modification of epoxy adhesive compounds on the mechanical properties of hot-dip galvanized steel sheet DX51+Z275 adhesive joints. The epoxy adhesives (resin and curing agent) were biochemically modified by lyophilized fungal metabolites (in the form of lyophilized fungal fractions or materials preparation containing low molecular weight secondary metabolites of lignocellulose-degrading white rot fungi (WRF) Pycnoporus sanguineus (L.) Murrill and prepared by two methods). The epoxy adhesives (epoxy resin Epidian 53 and poliaminoamide curing agent PAC) were biochemical modified by lyophilized fungal metabolites and prepared by two methods. In the first method (Method I), the epoxy resin and the curing agent were mixed with the fungal material in the desired concentration. In the second method (Method II), the resin was mixed with mortar-grounded lyophilized post-culture liquid of the desired concentration and after following thorough mixing, a suitable amount of the poliaminoamide curing agent was added. The single-lap adhesive joints were prepared by modified epoxy adhesive compounds and were cured in various climatic factors. The specimens of adhesive joints were cured at single stage at the same temperature and humidity as during adhesive bonding (Variant A and Variant B). At the second stage, Method I adhesive joints were seasoned for two months at the temperature of 50 °C and 50% humidity in a climate test chamber (Variant C). The shear strength tests of the single-lap adhesive joints were performed using a Zwick/Roell Z150 testing machine in accordance with the DIN EN 1465 standard. The analysis of results revealed that the addition of the biological modifier can lead to reduced adhesive joint strength in ambient conditions, yet at elevated temperature and the higher humidity it results in a significant increase in adhesive joint strength.

In this investigation, attempts are made to fabricate high performance polymer such as polybenzimidazole (PBI) (service temperature ranges from -260°C to +500°C) by nano silicate epoxy adhesive and to see its performance under space radiation. The polybenzimidazole sheets are fabricated by high performance nano adhesive i.e., by dispersing silicate nano powder into the ultra high temperature resistant epoxy adhesive (DURALCO 4703, the service temperature of the adhesive is -260°C to +350°C) with 2 to 20% weight ratios with the matrix adhesive. Prior to fabrication of polybenzimidazole sheet, the surface of the polybenzimidazole is ultrasonically cleaned by acetone followed by its modification through low-pressure plasma by using 13.56 MHz RF Glow Discharge with 30, 60, 120, 240 and 480 seconds at 100 W of power using nitrogen as process gas. It is observed that polar component of surface energy leading to total surface energy of the polymer increases with exposure time of low pressure plasma up to 120 seconds and then it saturates. Nano adhesive bonding of high performance polymer is exposed to two types of radiations (i) mixed field radiation for 24 hours at a dose rate of 37kGy/hr in the pool of a SLOWPOKE-2 (safe low power critical experiment) nuclear reactor and (ii) Co-60 irradiation with 100 % gamma radiation at a dose rate of 4 kGy/hr for 60 hours. Tensile lap shear strength reveals that when the polymer surface is modified by low pressure plasma, joint strength increases from 1 MPa to 13 MPa and increases further up to 23 MPa when the polymer is fabricated by nano silicate epoxy adhesive with increasing weight ratios of silicate nano powder up to 10% and then it deteriorates with the increasing weight ratio of silicate nano powder. When this nano silicate epoxy adhesive joint is exposed to high-energy radiation of mixed field, there is a further considerable increase in joint strength up to 30 MPa. However, when the nano silicate epoxy adhesive joint is exposed to 100 % gamma rays condition, joint strength deteriorates. Therefore, this is possible that mixed field radiation; basically increase the crosslink density of the adhesive resulting in increase in adhesive joint strength and in the second case: gamma radiation is detrimental and which could essentially makes chain scission to the basic adhesive and resulting in significant deterioration of joint strength. Finally, to understand the behaviour of nano silicate epoxy adhesive bonding of Polybenzimidazole, the fractured surfaces of the joints are examined by scanning electron microscope.

The friction coefficient was a key parameter for expressing the friction characteristics of the seal faces. The friction coefficient of the end faces of unbalanced mechanical seals with laser-textured micro-pores surface and spiral grooves surface were tested on the self-designed mechanical seal testing device, and compared with conventional smooth surface contacting mechanical seal. The experimental sealed medium was 25 °C water, the sealed medium pressures p=03 ∼ 0.9 MPa, and the rotating speeds n=1000 ∼ 3000 rpm. A series of experimental data of friction coefficient were obtained through experiments under different medium pressures and rotating speeds. The experimental results show that the friction coefficient of mechanical seals with laser surface micro-texturing were significantly lower than that of smooth surface mechanical seal, and the effect of spiral grooves end face on improve friction characteristics was better than that of micro-pores end face. Both medium pressure and rotating speed had influenced on the friction coefficient of mechanical seals with laser surface micro-texturing. The friction coefficient of micro-textured end face decreased with the increasing medium pressure, and it first decreased with the increasing rotating speed, and changes little when the rotating speed reaches a certain value.

Combined effect of surface pretreatment and nanomaterial reinforcement on the adhesion strength of aluminium joints

Additive manufacturing (AM) is often used for prototyping; however, in recent years, there have been several final product applications, namely the development of polymer-metal hybrid (PMH) components that have emerged. In this paper, the objective is to characterize the adhesion of single-lap joints between two different materials: aluminium and a polymer-based material manufactured by fused filament fabrication (FFF). Single-lap joints were fabricated using an aluminium substrate with different surface treatments: sandpaper polishing (SP) and grit blasting (GB). Three filaments for FFF were tested: acrylonitrile butadiene styrene (ABS), polyamide (PA), and polyamide reinforced with short carbon fibers (PA + CF). To characterize the behaviour of these single-lap joints, mechanical tension loading tests were performed. The analysis of the fractured surface of the joints aimed to correlate the adhesion performance of each joint with the occurred failure mode. The obtained results show the impact of surface roughness (0.16 < Ra < 1.65 µm) on the mechanical properties of the PMH joint. The ultimate lap shear strength (ULSS) of PMH single-lap joints produced by FFF (1 < ULSS < 6.6 MPa) agree with the reported values in the literature and increases for substrates with a higher surface roughness, remelting of the primer (PA and PA + CF), and higher stiffness of the polymer-based adherent.

The objective of this research is to study the damage behavior of bulk adhesive and single lap joint (SLJ) specimens during low cycle fatigue (LCF). Fatigue tests under constant stress amplitude were done and strain response was measured through cycles to failure using the bulk adhesive and SLJ data. A non linear damage model was used to fit experimental results. Identification of the damage parameters for bulk adhesive was obtained from the damage against accumulated plastic strain plot. It is shown that the plastic strain can be obtained from the constant stress test if the instantaneous elastic modulus, i.e. modulus affected by damage, is evaluated for each cycle. On the other hand, damage in SLJ was seen mainly in the adhesive for itself — no substrate failure — this fact is used to propose that fatigue response in the joint is due to continuum damage accumulation in the adhesive as the number of cycles increases. Damage behavior under compressive loads was not taken into account but good correlation of numerical and experimental data was obtained. It was found that damage evolution behaves in a non linear manner as the plastic deformation grows for each cycle: on fatigue onset an accelerated damage grow is observed, then a proportional evolution, and finally a rapid failure occurs; this characteristics were seen in both the SLJ and bulk adhesive specimen. So far, this research takes the damage model found in a standard adhesive specimen and assumes it is accurate enough to represent the damage behavior of the SLJ configuration.

Adhesive joints serve under thermal loads as well as structural loads. The different thermo-mechanical properties of the adhesive and adherend materials cause incompatible thermal strains along the adhesive and adherend interfaces. Consequently, nonuniform thermal stress distributions are observed in the adhesive joints. In case the adhesive joints are constrained, these thermal stresses become more evident even for a uniform temperature distribution. In practice the adhesive joints interact with fluids (air) with different temperature and velocity and experience conductive and convective heat transfers. The variable thermal boundary conditions introduce a new non-linearity in addition to the geometrical and material non-linearities which are observed in adhesive joints. The transient temperature distributions can be obtained by solving the energy equation under the thermal boundary conditions. The corresponding thermal strain and stress distributions can be calculated using the transient temperature distributions. The large displacement and rotations occurring in adhesive joints require the implementation of the small strain-large displacement theory to the elastic stress analysis. This study introduces a simple method for calculating the heat transfer coefficients between the fluid and adhesive joints and explains the implementation of the finite element method to the thermal analysis and the geometrical nonlinear stress analysis. The thermal stresses in the metal-metal adhesive single lap, tubular, metal-metal and composite tee joints were analysed for the variable thermal and specified structural boundary conditions. The variable thermal boundary conditions cause non-uniform temperature distributions through the adhesive lap joints; consequently, non-uniform thermal strain and stress distributions occur. The adherend and adhesive regions in the neighborhood of the adhesive-adherend interfaces were subjected to high stress concentrations.

Creep behaviour and tensile response of adhesively bonded polyethylene joints: Single-Lap and Double-Strap

Mechanism analysis of dual wavelength laser welding AlN-PC joint based on microtexture treatment

Experimental investigation of the effects of adhesive defects on the single lap joint strength

In aircraft structures, composite plate joints often present significant challenges. Mechanical fastenings such as pins, bolts, or rivets require holes to be drilled in the plates, which reduces the strength of the laminate due to stress concentrations around the hole edges. These joints frequently become sources of structural failure in aircraft. Therefore, the design of composite plate joints is crucial to maintain structural integrity. Adhesive joints offer several advantages over mechanical joints, including the ability to join two different materials, more uniform stress distribution along the joint, and reduced weight since no bolts or rivets are needed. The most common adhesive joint design is the Single Lap Joint (SLJ), which is popular due to its simple geometry and high structural efficiency. However, the main drawback of the SLJ is load eccentricity, which leads to secondary bending and undesirable normal stresses along the adhesive edges. The hypothesis of this study is that SLJ conditions with optimal shear strength can be achieved through the right combination of adhesive type, bond surface preparation, and joint configuration. This study analyzes the influence of various adhesive materials, joint designs, and manufacturing methods using numerical modeling methods, validated with analytical approaches and ASTM standard testing. Numerical modeling is conducted using the finite element method with a cohesive zone model (CZM) approach to examine stress distribution in various cases, such as the impact of geometry, adhesive thickness, and joint length. The normal and shear stress distribution along the joint is found to significantly affect the strength of the SLJ, highlighting the importance of careful design and material selection in these applications.

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.

PurposeThe purpose of this paper is to provide an insight into the techniques which are used and developed for adhesive bulk and joint specimens manufacturing.Design/methodology/approachAfter a short introduction, the paper discusses various techniques for adhesive bulk and joint specimens manufacturing and highlights their advantages and limitations. A number of examples in the form of different bulk and joint specimens of different types of adhesives are used to show the methods for determining the adhesive's mechanical properties needed for design in adhesive technology. In order to predict the adhesive joint strength, the stress distribution and a suitable failure criterion are essential. If a continuum mechanics approach is used, the availability of the stress‐strain curve of the adhesive is sufficient (the bulk tensile test or the TAST test is used). For fracture mechanics‐based design, mode I and mode II toughness is needed (DCB and ENF tests are used). Finally, single lap joints (SLJs) are used to assess the adhesive's performance in a joint.FindingsBefore an adhesive can be specified for an application, screening tests should be conducted in order to compare and evaluate the various adhesion parameters. Properties of adhesives can vary greatly and an appropriate selection is essential for a proper joint design. Thus, to determine the stresses and strains in adhesive joints in a variety of configurations, it is necessary to characterize the adhesive behaviour in order to know its mechanical properties. A great variety of test geometries and specimens are used to obtain adhesive properties. However, for manufacturing of adhesive bulk specimens and joints necessary for use in these tests, properly, moulds should be designed.Originality/valueThe paper summarises the main methods of preparing adhesive bulk and joint specimens and the test methods for determining the mechanical properties needed for design in adhesive technology. Emphasis is given to the preparation of specimens of suitable quality for mechanical property determination and the moulds designed for this purpose.