Effect Of Adhesive Thickness Research Articles

Investigation on bending collapse behavior of similar and dissimilar Aluminum-Steel hat-section sandwich beams jointed by structural adhesive: An experimental, numerical and theoretical study

A significant feature about the application of adhesive joints in various structures is their ability to join dissimilar materials, thus effectively maintaining the structural integrity regardless varying loads. In this paper, the bending collapse behavior of adhesively bonded hat section sandwich beam (HSSB) structures with using of aluminum and steel were investigated. Four configurations of HSSB with different materials for the upper hat beam and lower plate were subjected to quasi-static three-point bending tests as part of the experimental investigation. In comparing the specific absorbed energy (SEA) of the beams, a sample of a hat section sandwich beam with a steel upper hat and an aluminum lower plate had a higher SEA value despite the load-displacement and bending collapse behavior similar to the hat section sandwich beam with a steel upper hat and a steel lower plate. subsequently, a finite element model was developed for bending collapse analysis and a theoretical prediction based on the Kecman model was presented to investigate the hinge moment on HSSB. Based on this, the findings of the numerical study and the predicted theoretical model were in good agreement with the experimental results. The effect of adhesive thickness, the identical mass, and the thickness of the upper hat and lower plate were examined for the purpose of performing an in-depth analysis of the influencing parameters in HSSB structures.

Modeling and testing of a highly sensitive surface acoustic wave pressure sensor for liquid depth measurements

The fluid depth/level measurement application extends from industry to domestic contexts. This article explores the underutilized potential of Surface Acoustic Wave (SAW) sensor-based devices for liquid depth and pressure measurements. Experiments conducted at room temperature address design challenges using a quartz Y34° cut single-port resonator. Theoretically predicted longitudinal strain sensitivity of −1.15 kHz/μStrain (−1.32 ppm/μStrain) was reduced to −421 Hz/μStrain (-0.48 ppm/μStrain) due to adhesive layer thickness. Numerical simulations investigate the effect of adhesive thickness on strain transfer from a cantilever to the Surface Acoustic Wave (SAW) sensor's top surface. The sensor is tested on a cantilever and integrated into a 20 μm thick diaphragm-based depth gauge, achieving a depth sensitivity of 42 Hz/mm (0.048 ppm/mm). This sensitivity results from bending of the SAW sensor under hydrostatic pressure, causing compression at the top SAW surface, which was an interesting observation. Additional numerical investigations confirm this behavior, aligning well with experimental findings. The article summarizes the comprehensive study of the SAW resonator’s performance and effect of adhesive thickness and provides a guide for designing thin diaphragm-based SAW pressure and depth sensors. It also identifies the device’s high sensitivity compared to other sensors in the literature and outlines potential avenues for future research.

Effect of adhesive thickness and loading speed on bonding strength in single-lap adhesive joints with aluminum 5754-H111

This study provides shear test results of single-lap adhesive joints with aluminum 5754-H111. To investigate the effect of adhesive thickness on joint strength in single-lap adhesive joints, three different thicknesses (0.2, 1, and 2 mm) were applied. Increasing the adhesive thickness from 0.2 mm to 1 mm and from 0.2 mm to 2 mm resulted in a reduction in shear load of roughly 36% and 44%, respectively. It has been observed that the joint strength decreases with increasing adhesive thickness in single-lap adhesive joints with aluminum 5754-H111. In addition, single-lap adhesive joints were tested at various loading rates (1, 10, and 100 mm/min), and the influence of loading speed on adhesive strength was studied. The shear load increased with the loading speed in the test results of single-lap adhesive joints.

Experimental study and numerical simulation of adhesively bonded timber-concrete composite panels: bending behavior, adhesive shear and peel stress distributions

This study investigated the structural response of timber-plain concrete panels bonded with epoxy and PUR adhesives under a four-point bending load, both experimentally and numerically. Tests evaluating epoxy- and PUR-bonded glulam-plain concrete panels measured ultimate load (Fult), effective bending stiffness (EIeff), and mid-span deflection (∆ult). Shear stress within the adhesives was monitored using fiber optic sensors. Numerical simulations estimated Fult and EIeff with errors of 5% and 14%, respectively. These discrepancies may stem from assuming defect-free wood (e.g., no knots), idealized boundary conditions, uniform adhesive thickness assumptions, and unmeasured mechanical and damage properties of wood and concrete (Detailed error source analysis is available in Section 4). Qualitative validation involved comparing sensor-recorded shear stress with simulation results. A parametric study evaluated the effects of adhesive thickness (0.5, 1, and 3 mm), concrete-wood depth ratio (50/85, 85/85, and 150/85 mm/mm), wood type (spruce (Picea), beech (Fagus), and Azobe (Lophira)), concrete strength class (C12/15 and C30/37), and span length (2, 4, and 8 m) on the bending behavior of the panel, and the shear and peel stress distribution within the adhesive bond line. Shear stress prevailed over peel stress in the adhesives, with peel stress approaching shear stress as span length increased (max. τa / max. σa ∼ 3.5–7). The ultimate load typically resulted in concrete compression damage and wood fiber damage, influenced by the concrete strength class and wood type. Higher depth ratios led to tension damage in concrete, while adhesive thickness had a minimal impact on stress distribution and failure modes.

Enhancing fatigue life of steel plates with CFRP laminate: Effects of curing temperature, stress range, and adhesive thickness

Steel bridges often require rehabilitation and retrofitting to address cracks and deteriorations caused by age, environmental factors, and increased loads. Carbon fibre reinforced polymers (CFRP) strengthening is a reliable and efficient method used for strengthening steel structures, particularly in steel joints subjected to cyclic loading from traffic. This study explores the impact of adhesive curing temperature on the fatigue behaviour of CFRP-steel joints under various stress ratios and ranges, it also evaluates the effect of adhesive thickness on fatigue life of the joint. Results indicate that curing temperature has no effect on fatigue behaviour, and the stress range-fatigue limit is constant at 30 MPa. Strain readings were taken to monitor debonding initiation, and the failure mode was predominantly steel-adhesive debonding. Adhesive thickness <2 mm has no significant effect on fatigue life of steel joints strengthened with CFRP. This research provides valuable insights for improving durability of steel bridges and structures.

Effect of Adhesive Thickness on the Mechanical Property of Adhesively Bonded Corrugated Structure under Three-point Bending Load

Effect of Adhesive Thickness on the Mechanical Property of Adhesively Bonded Corrugated Structure under Three-point Bending Load

A new technique to measure shear fracture toughness of adhesives using tensile load

The end notched flexure (ENF) test is the most common method for measuring the mode II fracture energy of adhesives which provides reliable results but has some inherent problems. The shear fracture energy calculated using ENF for brittle adhesives is often based on a single data point (corresponding to the fracture load) obtained from the test where the crack grows catastrophically and the results are significantly sensitive to pre-crack tip conditions. The aim of the current study is to introduce a new pure mode II fracture test suitable for measuring the shear fracture energy of adhesives. A new technique for measuring the mode II critical strain energy release rate (SERR) of brittle adhesives is proposed based on the central cut ply (CCP) configuration. Fracture tests were carried out on adhesively bonded steel CCP specimens. It is shown that the crack growth in CCP joints is more stable, and the failure develops in multiple steps that generates more experimental data point during the crack propagation. The mode II fracture energy of a brittle epoxy-based adhesive is extracted using CCP method and is compared with the shear fracture energy obtained from the ENF tests. The effect of adhesive thickness on the obtained fracture energies is also analyzed. The CCP technique can be used to find both the crack initiation and crack propagation toughness values whereas the ENF method only provides the crack initiation fracture energy.

Adhesively bonding a reusable PZT transducer for structural health monitoring (SHM) with an ethylene-acrylic acid copolymer adhesive

A novel approach to bonding a piezoelectric lead zirconate titanate (PZT) transducer on a structure for health monitoring was developed to replace the traditional method of bonding PZT permanently. Several experiments demonstrated the feasibility of a reusable PZT transducer based on the adhesive film made using ethylene-acrylic acid copolymer (EAA). Additionally, the adhesion performance of using EAA for bonding PZT at different temperatures and the effect of heating temperature on reusable PZT transducer removal from the test structure was investigated. The effect of adhesive thickness on the mechanical property and the performance of PZT has also been explained. Experimental results showed that the optimized heating temperature of the adhesive film was around 140 °C due to the stability of PZT being sensitive to high temperature and the ease of removing PZT from the test structure without damage. An analysis of the varying thickness of the adhesive layer on PZT performance indicated that the amplitude of Lamb wave signals changed with adhesive thickness, increasing with greater adhesive thickness. Therefore, the adhesive layer made using EAA provides a new approach to conducting Lamb wave-based structural health monitoring.

Performance of Glass to Iron-based Shape Memory Alloy Adhesive Shear Joints with Different Geometry

Previous research has shown that glass beams with external, mechanical post-tensioning along their edges show better structural performance than glass beams without any such reinforcement. The initial and post-fracture load-bearing capacity of glass beams can be increased by reinforcing them with stainless steel or fiber-reinforced plastic (FRP) tendons that are post-tensioned and connected to the beam edges. However, post-tensioning of stainless steel or FRP bars or strips is complex and challenging because it often requires special setups, such as hydraulic jacks. Iron-based shape memory alloys (Fe-SMAs) are promising post-tensioning materials due to their efficient activation procedure and good mechanical properties. The target prestress level can be introduced by heating the Fe-SMA to a specific temperature followed by cooling down naturally to ambient temperature. As a contribution to assessing the feasibility of strengthening glass elements with adhesively bonded Fe-SMA strips, this paper focuses on the bond behavior of glass-to-Fe-SMA lap-shear joints based on numerical investigations. A finite element model is developed to evaluate the effect of adhesive thickness, Fe-SMA strip thickness and bond length on the structural behavior of glass to Fe-SMA lap-shear joints.

Experimental Bond Behaviour of Glued-In Rod Connection for Mengkulang Glulam under Pull-Out Loading

Mechanical joint and adhesive joint are the two most common types of timber connections. In the case of timber construction, bonded-in rods offer a long-term, aesthetically acceptable alternative to some of the more conventional steel moment connections. Bonded-in rod connections in timber need many desirable attributes inefficiency, manufacture, performance, aesthetics and cost. This paper presents pull-out experimental testing for glued-in rod made of Mengkulang (tarrietia javanica) glulam joints. Hundred and seven (107) specimens were prepared, each with a single glued-in rod parallel and perpendicular to the grain. The steel treaded rod with a diameter of 12 mm, 16 mm and 20 mm with three numbers of adhesive (Sikadur-30) thicknesses of 2 mm, 3 mm and 4 mm were used in this experiment. The pull-out tests observations were on the effects of adhesive thickness, parallel and perpendicular grain directions and modes of failure of the specimens. The result obtained that 4 mm adhesive thickness was the strongest and parallel specimens showed better results than the perpendicular specimens. The pull-out failure modes are affected by the selected factors, i.e. the adhesive thickness, rod diameter and grain directions. Most of the specimens show failures in the timber besides the adhesive to timber interface.

Strength and failure mechanism of single-lap magnesium-basalt fiber metal laminate adhesively bonded joints: Experimental and numerical assessments.

A quick literature search reveals the significant lack of data and information concerning magnesium-to-magnesium bonded joints as well as fiber-metal laminates (FMLs) made with magnesium alloys. Therefore, a systematic series of experimental and numerical investigations are carried out to assess the performance of single-lap joints mating FML adherends. The primary goal is to better understand the effects of geometrical and material parameters that influence the performance of magnesium-to-magnesium joints. The FML adherends used in this study consist of basalt natural fiber-epoxy laminate sandwiched in between thin sheets of magnesium alloys, which were subsequently adhesively bonded using a room-cured epoxy resin. The effects of two types of surface treatments, namely, “sandblasting” and “sandblasting with resin coating” on the bond strength and failure mechanism of the adhesively bonded joints (ABJs) are investigated. A 3D numerical model developed to simulate the response of the joints subjected to quasi-static lap-shear tests. This model, which accounts for the material and geometrical nonlinearity in the joints, is used to perform a parametric analysis for establishing the optimal overlap bond length. The distributions of the shear and peel stresses in the overlap region and the effects of adhesive thickness on the performance of the joints are systematically examined. The comparison of the experimental data and numerical results confirms the robustness and cost-effectiveness of the numerical model in predicting the response of such single-lap ABJs.

Integrated modelling method of bonding strength and residual life prediction for selective repair structure of aluminium alloy

To accurately describe and predict the overall strength and residual life of selective repair bonded structures, an integrated simulation model of crack propagation including bonding strength is established. Based on two methods, an integrated simulation model including a cohesive zone method model for predicting the residual life of a selective repair structure is established. By comparing the computational efficiency and accuracy of both the stress intensity factor and residual life of selective repair structures using different calculation methods, the modelling scheme is optimised. Based on this optimised scheme, the effect of adhesive thickness on the stress intensity factor and residual life of the repair structure is analysed. FM94 adhesive measuring 0.2–0.4 mm thickness is used to decrease the stress intensity factor and improve the remaining life such that material utilisation efficiency is guaranteed.

Mode I Crack Propagation Experimental Analysis of Adhesive Bonded Joints Comprising Glass Fibre Composite Material under Impact and Constant Amplitude Fatigue Loading

The T-90 Calima is a low-wing monoplane aircraft. Its structure is mainly composed of different components of composite materials, which are mainly bonded by using adhesive joints of different thicknesses. The T-90 Calima is a trainer aircraft; thus, adverse operating conditions such as hard landings, which cause impact loads, may affect the structural integrity of aircrafts. As a result, in this study, the mode I crack propagation rate of a typical adhesive joint of the aircraft is estimated under impact and constant amplitude fatigue loading. To this end, effects of adhesive thickness on the mechanical performance of the joint under quasistatic loading conditions, impact and constant amplitude fatigue in double cantilever beam (DCB) specimens are experimentally investigated. Cyclic impact is induced using a drop-weight impact testing machine to obtain the crack propagation rate (da/dN) as a function of the maximum strain energy release rate (GImax) diagram; likewise, this diagram is also obtained under constant amplitude fatigue, and both diagrams are compared to determine the effect of each type of loading on the structural integrity of the joint. Results reveal that the crack propagation rate under impact fatigue is three orders of magnitude greater than that under constant amplitude fatigue.

The bonding performances of carbon nanotube (CNT)-reinforced epoxy adhesively bonded joints on steel substrates

Carbon nanotubes (CNTs) are generally considered as a promising particle reinforcement of incorporating advanced properties and characteristics into epoxy nanocomposites. This paper investigated the bonding performances of CNT-reinforced epoxy adhesively bonded joints on steel substrates using the single lap shear (SLS) tests. The bonding performances (including bonding strength, fracture strain, toughness, and failure mode) were studied with three adhesive thicknesses (1 mm, 0.5 mm, and 0.25 mm) and three CNT weight fractions (0%, 0.375%, and 0.75%). The experimental results indicated that thinner bondlines and higher CNT additions could significantly improve the bonding performances and modify the failure mode of CNT-reinforced epoxy adhesively bonded joints. However, the effects of adhesive thickness became less significant with the increase of CNT weight fractions. In addition, the plastic behaviour of CNT-reinforced epoxy, CNTs pulling-out, and the aggregation of CNTs were observed by scanning electron microscopy (SEM) image analysis on the fracture surfaces of CNT-reinforced epoxy adhesively bonded joints, indicating the potential effectiveness of the CNT reinforcement.

Structural integrity of adhesively bonded 3D-printed joints

Fabrication of polymeric components with complex geometry has been increased in the recent years. As additive manufacturing (AM) showed its unique capabilities, it has been widely used in production of geometrically-complex parts. Although various types of bonding have been developed, utilizing adhesive joints is common in different polymeric structures. In the current study, influence of 3D printing parameters and adhesive thickness on the performance of adhesively bonded joints have been studied. To this aim, we have used fused deposition modeling (FDM) process and polylactic acid (PLA) material to fabricate single-lap joints. The specimens are fabricated under different printing conditions to determine influence of printing parameters on the mechanical behavior of the joints. Moreover, adhesive with three different thicknesses was used to investigate effect of adhesive thickness on the structural integrity of the 3D-printed joints. Additionally, a series of finite element analysis was performed and agreement between experimental observation and numerical results has been documented. As FDM process has garnered significant attention, the outcomes of this study can be used for further development.

Effect of the adhesive thickness on butt adhesive joints under torsional loads

Adhesive joints are extensively used in diverse industrial applications, exploiting the improved mechanical performance they offer over classical mechanical joining methods. To effectively design adhesive joints, it is first necessary to determine the mechanical properties of the materials being used (e.g. the adhesives and adherends). In this work, an epoxy based structural adhesive was characterized under tensile and shear loads using butt joints with solid adherends. The tensile tests were performed in a universal tensile machine and the shear tests were carried out in a torsional testing machine that ensures perfect alignment of the specimens and avoids any spurious bending moments, compression and tension loads during the test. The effect of adhesive thickness on the tensile and shear properties of the adhesive was evaluated, showing that under torsional loads there is a significant effect of the adhesive layer thickness on the shear strength and stiffness of the adhesive.

Effects of surface treatment and adhesive thickness on the shear strength of precision bonded joints

In the present work single-lap-joint specimens with an adhesive layer of micron-scale thickness were prepared, and the effects of adhesive thickness and surface treatments (Milling, SAA, PAA, and SB + SAA) on the bond strength were investigated by tensile tests and surface analyses. The shear strength increases with the increase of adhesive thickness for the milling surface, while it is not presented for the other treated surfaces. PAA treatment can significantly improve the bond strength, while the sandblasting treatment cannot despite the surface roughness greatly increased. The bond strength depends on many surface characteristics, such as the peak density, nano-scale pores, and texture direction, instead of only the roughness value or wettability. The shear energy consumption of the single-lap joints is positively correlated with the shear strength, which evaluates the surface treatment methods for improving the bond strength at a thin adhesive thickness as PAA > Milling > SB + SAA > SAA.

Numerical simulation and experimental analysis of vibration characteristics of heterogeneous sheet structure with adhesive

The use of steel-aluminum heterogeneous sheets and its adhesive-coated hemming process for cover parts helps to realize the lightweight of the car body, and its vibration characteristics greatly affect the NVH characteristics of the vehicle. Traditional cover parts vibration characteristics research ignores the influence of adhesives. Facing the higher performance of lightweight cover parts systems, it is necessary to establish a “sandwich”; multi-material structure model consisting of aluminum outer sheet-ductile structural adhesive layer-steel inner sheet. Based on the typical straight edge-flat surface unit structure of cover parts, this paper established a calculation model for the vibration characteristics of steel-aluminum heterogeneous sheet adhesive structure, and the effect of adhesive thickness is quantified through experimental verification. The results show that the natural frequencies of the finite element calculation model and the experimental model are highly consistent in the first two modes, and the first two natural frequencies become larger as the thickness of the adhesive increases. The shell element of finite element calculation model based on the laminated sheet vibration theory can effectively simulate the calculation of the first two modes of the steel-aluminum heterogeneous sheet adhesive structure.

Failure analysis of a composite wind turbine blade at the adhesive joint of the trailing edge

The trailing edge (TE) failure of a commercial wind turbine blade (WBT) is investigated in this article. The effect of adhesive thickness and band width on the TE failure is one of the most important issues in WTB production governing the integrity and soundness of the WTB structure. Different static load cases of a WTB are identified under various operating conditions as a case study. Static analysis is performed on a full 3-D finite element model of the blade and the critical region of its TE is determined. Then, sub-part modeling is performed focusing on the critical region of the TE. Adhesive joint in the constructed model is modeled using cohesive zone modeling (CZM). The failure of the adhesive joint with different dimensions of adhesive is examined under normal wind condition and gust condition. Taking into account the production limitations, the proper dimensions of the adhesive withstanding different conditions of the WTB are extracted.

Experimental investigation of the effects of adhesive thickness on the fracture behavior of structural acrylic adhesive joints under various loading rates

Designing joints requires a clear understanding of the appropriate thickness of the adhesive used. Structural acrylic adhesives have rarely been studied in terms of their thickness effect on the joint performance. To this end, the fracture resistance of a second-generation acrylic (SGA) adhesive was experimentally investigated by conducting a double cantilever beam (DCB) test. Because the SGA adhesive whitened when plastically deformed, the change of the plastic region with the crack growth was visualized. Therefore, the relationship between the fracture energy and the adhesive thickness was explained in terms of the plastically deformed area. With a thinner adhesive layer, the entire layer was whitened, and a linear relationship was obtained. In this region, the fracture energy increased from approximately 2 kJ/m2 with an adhesive thickness of 0.2 mm to approximately 4 kJ/m2 with 0.6 mm thickness. With more increase in the thickness, the fracture energy increased over 8 kJ/m2. Increasing the thickness, however, resulted in partial whitening, yielding a non-linear relationship. Moreover, increasing the loading rate changed fracture behavior. At the opening speed of 2.5 m/s, stick-slip crack propagation was observed in any adhesive thickness, and the critical fracture energy dramatically decreased. In contrast, the arrest fracture energy under unstable crack propagation was independent of the loading rate and the adhesive thickness as approximately 1 kJ/m2.