Shear Strength Of Adhesive Joints Research Articles

Effect of epoxy resin and hardener containing microcapsules on healing efficiency of epoxy adhesive based metal joints

Dual component microcapsules of epoxy resin and polyamine hardener with polymethyl methacrylate (PMMA) shell were synthesized using a water-oil-water emulsion solvent evaporation method. The high concentration of sodium dodecyl sulfate (SDS) was used to reduce the thickness of shell wall of dual component microcapsules. The dual microcapsules of 1:1 weight ratio were introduced in the epoxy adhesive to study the healing effect. The morphology, chemical structure and thermal characteristics of the microcapsules were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA), respectively. The insertion of dual component microcapsules in epoxy matrix reduced the lap shear strength of adhesive joints, which may be attributed to the generation of stress concentration cites because of micron sized capsules. However, the extension and absorbed failure energy of adhesive joints under uniaxial loading increased with the increase of concentration of dual microcapsules. The viscoelastic nature of the dual microcapsules may be responsible for this enhancement. Significant enhancement in the healing efficiency (90.93%) of the joints was achieved for 10 wt% of dual microcapsules. The crack pinning and crack blunting mechanisms at the vicinity of the crack path adjacent to the microcapsules were found responsible for significant enhancement in the healing efficiency of the adhesive joints.

Using Non-Destructive Testing to Determine the Correlation between Dynamic Mechanical Properties and Bonding Strength of Wood-Plastic Composite Adhesive Joints

Wood-plastic composites (WPC) have been developed into new and important wood-based composites because of their benefits for the environment, economy, and recyclability. When combined with structural adhesives, WPCs will have a greatly broadened application in the construction field. In this work, epoxy resin and acrylic ester were used to bond WPC adhesive joints. The shear strength of the adhesive joints was determined and investigated. Resonant frequency and dynamic modulus of elasticity (MOE) of the WPC adhesive joints were measured using the longitudinal vibration method. The correlation between different vibration parameters and shear strength of WPC adhesive joints was also investigated. Results showed that the epoxy resin had a better bonding quality than the acrylic ester on the bonding of WPC adhesive joints. The resonant frequency, dynamic MOE, and the dynamic MOE ratio of the WPC adhesive joints had close correlations with their shear strength for the samples bonded with epoxy resin.

RESISTÊNCIA AO CISALHAMENTO DAS JUNTAS ADESIVAS PRODUZIDAS COM TRÊS DIFERENTES ESPÉCIES DE MADEIRAS E ADESIVOS VINÍLICOS PARA APLICAÇÕES NÃO ESTRUTURAIS

Os adesivos utilizados na colagem de madeiras para aplicações não estruturais normalmente contêm uma emulsão de poli(acetato de vinila) (PVAc) estabilizada com poli(álcool vinílico) e alguns aditivos. A ligação adesiva formada com essa classe de adesivo é pobre quando exposta à umidade e à temperatura. Nesse contexto, a classificação prévia dos adesivos utilizados para aplicações não estruturais, com resistência à umidade e à temperatura, é muito importante para a qualidade e durabilidade das juntas adesivas. Neste trabalho, foi estudada a influência de três espécies de madeiras (Fagus sylvatica L., Mimosa scabrella Bentham e Micropholis cf. venulosa Mart. & Eichler) na resistência ao cisalhamento das juntas adesivas preparadas com três adesivos vinílicos, sintetizados com diferentes concentrações do N-butoximetilacrilamida (NBMA). Os ensaios de resistência ao cisalhamento, na linha de colagem, foram realizados sob diferentes ciclos de acondicionamento das juntas adesivas. Os resultados indicaram que há diferenças significativas na resistência de colagem das juntas adesivas e na porcentagem de falha na madeira provocada, tanto pela espécie de madeira quanto pelo tipo de adesivo utilizado. Os adesivos produzidos foram classificados de acordo com a classe de durabilidade, após várias etapas de acondicionamento. Os valores mais altos de resistência ao cisalhamento foram observados nas juntas coladas com as madeiras de Micropholis cf. venulosa Mart. & Eichler e Fagus sylvatica L., com o adesivo AD-3. O menor valor de resistência ao cisalhamento foi observado nas juntas adesivas preparadas com a madeira da espécie Mimosa scabrella Bentham. A madeira Micropholis cf. venulosa Mart. & Eichler mostrou-se mais adequada para a substituição da madeira Fagus sylvatica L.

A replacement of chromate coating for adhesive bonding of stainless steel in a corrosive environment

For adhesive bonding of stainless steel to itself, a surface treatment involving chromates is used. However, chromates are environmentally unfriendly so a replacement is being sought. In this paper, an alternative to chromate was investigated. The standard test method, ASTM D 1002, was used to measure the failure load of adhesively bonded stainless steel samples. A general-purpose epoxy adhesive was used. To simulate marine exposure, adhesively bonded samples were placed in a 5% salt spray for extended periods of time, up to five weeks. Results indicated that the initial shear strength of adhesive joints prepared with a traditional chromate preparation was 25% greater than the new, alternative coating. However, more importantly, the rate of decrease in strength with salt spray exposure was greater for the chromate than for the alternative. After 21 days, both bonding surface treatments had the same strength. However, after this period of time, the alternative was stronger than the chromate treatment, indicating that the alternative was a more durable coating. An adhesive/adherent coated system was investigated using a finite element method in order to investigate the influence of adhesive thickness between the adhesive and the adherent, and the residual stress in the adhesive layer. Keywords: Adhesive, Alternative Coating, Crevice Corrosion, Potentio-Dynamic, Salt Spray.

Fracture Characteristics of Shear Adhesive Dissimilar Joint

In this study, the effect of bond thickness upon shear strength and fracture toughness of epoxy adhesively bonded joint with dissimilar adherents was addressed. The bond thickness, t between the adherents was controlled to be ranged between 0.1 mm and 1.2 mm. Finite element analyses were also executed by commercial ANSYS 11 code to investigate the stress distributions within the adhesive layer of adhesive joint. As a result, shear strength of adhesive joint reduces with increasing bond thickness. The strength of shear adhesive joint was also depended on elastic modulus of adherent. Moreover, the failure of dissimilar adherents bonded shear joint originated at a location with critical stress-y which was the interface corner of ALYH75/epoxy. In the case of shear adhesive joint with an interface crack, the fracture also occurred at the ALYH75/epoxy interface even in the steel-adhesive-aluminum (SEA) specimens. Fracture toughness, Jc of aluminum-adhesive-steel (AES) joints was similar to those of SES and demonstrates strong dependency upon bond thickness. Furthermore, the interface crack in SEA specimen has relatively large fracture resistance if compared to those in AES specimen. Finally, Kc fracture criterion was found to be appropriate for shear adhesive joints associated with adhesive fracture.

Glass/epoxy composites and aluminium alloy joint using Kevlar® intermediate layer and nanoclay-reinforced epoxy adhesive

Adhesive lap joint between glass fibre/epoxy composites and aluminium alloy (2014 T4) was prepared by an in situ moulding process using a matched die mould. The surface of aluminium alloy was treated with chromic acid before adhesive bonding. Lap shear strength and fatigue life were evaluated in tensile mode and tension–compression mode (at 40% of lap shear load of adhesive joint), respectively. Knurling on the surface of aluminium alloy improved the lap shear strength of the adhesive joint but did not influence the fatigue life of the same. Lap shear strength and fatigue life of adhesive joint made with neat epoxy adhesive and reinforcement of an intermediate layer of Kevlar® between glass/epoxy composite and aluminium alloy were observed to be 0.44 kg/mm2 and 3.6 × 105 cycles, respectively. In another case, lap shear strength and fatigue life of similar type of adhesive joint made from nanoclay (Cloisite 30B)-reinforced epoxy adhesive and without reinforcement of an intermediate layer of Kevlar® were observed to be 0.38 kg/mm2 and 2.3 × 105 cycles, respectively. Whereas, lap shear strength and fatigue life of adhesive joint made from nanoclay-reinforced epoxy adhesive along with the reinforcement of an intermediate layer of Kevlar® were 0.48 kg/mm2 and 3.9 × 105 cycles, respectively. Therefore, adhesive joint made from nanoclay-reinforced epoxy adhesive along with the reinforcement of an intermediate layer of Kevlar® was the best.

Thermal Degradation of Silicone Sealant

The kinetics of thermal degradation of a polyorganosiloxane sealant was studied by the thermogravimetric analysis (TGA) method at three constant heating rates (2, 5, and 20 deg/min). An investigation was also made of the change in shear strength of adhesive joints in the course of heat ageing at temperatures ranging from 250 to 340°C. The data obtained were processed by the non-linear regression method. The process of thermal degradation proceeds in two stages. The first stage has an activation energy of about 140 kJ/mol and is accompanied with increase in the strength of the adhesive layer. The second stage with a higher activation energy (roughly 230 kJ/mol) causes a sharp fall in strength of the adhesive layer. A possible mechanism of the thermal degradation process is discussed.

Influence of the viscosity of UF resins on the radial and tangential penetration into poplar wood and on the shear strength of adhesive joints

Abstract This paper is the final part of a series reporting on the penetration (P) and bonding behaviour of urea-formaldehyde (UF) resins of different viscosities based on different degrees of condensation (DCs). The various resins were applied onto radial and tangential wood surfaces, and solid wood assemblies were prepared by hot pressing. Pt and Pr were observed by evaluation of photomicrographs of the bond lines. The mean and maximum depth of penetration was inversely proportional to the DC. The average depth of Pt was found to be slightly higher than Pr because of the abundance of pits on the radial walls. However, the maximum P was higher in radial direction, due to the elliptic shape of vessels in poplar as well as due to rays improving the resin flow. The lap shear strength (σm) of the same bonded assemblies was determined. Despite the fact that the wood failure always was very high, the σm increased with the better penetration of the resins with low viscosity. The higher strength values measured has been interpreted as a fortification effect of the interphase by bulk resin penetration, as cell wall penetration cannot be expected due to the large size of such resin molecules.

Effects of plasma modification on adhesion properties of wood

The study investigated the use of dielectric barrier discharge for surface modification to improve adhesion properties of Shorea contorta (white lauan), Gmelina arborea (yemane) and Acacia mangium. Wood specimens were exposed to oxygen plasma at intensity levels ranging from 5.8 to 46.5 kW min/m 2 to improve adhesion of phenol formaldehyde, urea formaldehyde resins and polyurethane coating. Work of adhesion was calculated based on contact angle measurements to determine thermodynamic changes on plasma modified wood. Surface characteristic was evaluated using atomic force microscopy (AFM). Results of the study showed that plasma modification resulted in significant improvement in work of adhesion for the three wood species investigated. Mechanical tests of plywood and wood laminates using plasma treated S. contorta glued with phenol or urea formaldehyde resins indicated improvement in shear strength of adhesive joints. No improvement or decrease in shear strengths were observed for plasma treated G. arborea and A. mangium. Pull off strengths of polyurethane coating on plasma treated S. contorta and A. mangium specimens showed slight improvement in strength of coated film. Effects of plasma treatment on adhesion properties of wood appear to be species specific and vary with process parameters.

609 エポキシ系異材継手のせん断強度及び破断特性の評価(OS10-(1)オーガナイズドセッション《材料損傷の機構・実験評価》)

In this paper, the effect of bond thickness upon the shear strength of epoxy adhesively bonded joints with dissimilar adherends is addressed. The bond thickness, t between the adherends is controlled to be ranged from 0.1 mm to 1.2 mm. Finite element analyses are also executed by ANSYS 11 code to investigate the stress distributions in adhesive layer of adhesive joints. The order of stress singularity is obtained from the analytical solution of Bogy's characteristics equation. As a result, shear strength of adhesive joint reduces with increasing bond thickness. Moreover, the failure of dissimilar adherends bonded shear joint has been initiated at a location with critical stress singularity order which is the interface corner of aluminium/adhesive. It is found that the shear strength prediction can be satisfactorily done by interface corner toughness, Hc parameter.

Composite adhesive joints of hardmetals with steel

Newest developments in the field of gluing and processing of plastics permit obtaining adhesive materials with profitable properties: high mechanical parameters, increased thermal conductivity, low electrical resistivity, increased rigidity, limited residual stresses or reduced creep [1] , [2] . This is possible by composite structure of adhesives, i.e. binders enriched with filling materials – additional phases of different kind, grain size and fraction. In the paper, effect of reinforcing adhesive materials with continuous and powdery fillers on shear strength of adhesive joints is discussed. Presented are also results of electron microscopy examinations and EDX analysis.

Dynamic shear strength of adhesive joints made of metallic and composite adherents

The use of adhesive joints has gained good acceptance in the automotive and aerospace industries in recent years, particularly for joining glass fiber reinforced plastics (GFRP) to metals. Such joints will be subjected to short duration dynamic loads in service. The present study focuses on the evaluation of the shear strength of adhesive joints prepared using four different commercial adhesives at loading rates in the range of 0.6–1.2 MPa/μs. The adhesives used were Araldite 2014, Araldite 2011, Epibond 1590 and A/B Loctite 324. Joints were prepared with two different adherent combinations; aluminum–aluminum and aluminum–GFRP. The results of the study indicated that, depending on the adhesive and adherent combination, the dynamic strength was 2–4 times the static strength. Among the four adhesives, Epibond 1590 exhibited the highest rate sensitivity whereas Loctite 324 exhibited the least. Further it was also observed that the dynamic strength was not sensitive to the adherent combination whenever the failure was predominantly within the adhesive layer.

Kompozycje epoksydowe sieciowane kompleksami imidazoli z kationem Cu(II)

The compositions of Epidian 6 epoxy resin cured with latent hardeners: complexes of imidazoles [2-methylimidazole (2M) or 2-ethyl-4-methylimidazole (2E4M)] with Cu(II) cations, or for comparison with Mg(II) cation and non-complexed 2M or 2E4M imidazoles (Table 1), were prepared. Pot lifetime and thermal parameters characterizing curing process, namely enthalpy and temperature of maximum heat effect (Table 1 and 2, Fig. 1) were investigated. The use of complexes of imidazoles with Cu(II) cation shifts this temperature upward 35-49 °C and extends pot lifetime of the composition at ambient temperature even 30 times. Static mechanical properties at tension and bending of casts made of the compositions discussed were determined (Table 3 and 4). Shear strength of adhesive joints based on the compositions has been evaluated. Shear strength at room temperature does not depend on curing agent type. However, at temp. 120 °C complexes of latent hardeners let reach much better shear strength than that caused by non-complexed imidazoles, especially 2M (Table 5).

Investigation of the relationship between statistical characteristics of substrate surface roughness and the strength of adhesive joints

The relationship between statistical characteristics of butadiene styrene rubber (BSR) surface roughness and shear strength of adhesive joints has been investigated. The assumption of stationary normal distribution of coordinates of surface points was made to determine the statistical characteristics of surface roughness. The profile length above the selected level l 1 (u) was introduced as a new surface roughness parameter to characterize adhesive penetration depth. The validity of simulated l 1 (u) value was verified experimentally. A good correlation between experimental and calculated results was found. A relationship between adhesive penetration depth and the bonding pressure during adhesive joint preparation was also obtained. The dependences among lap shear joint strength, bonding pressure and roughness characteristic l 1 (u) were determined.

Evaluation of Impact Shear Strength of Adhesive Joints with the Split Hopkinson Bar.

The shear strength of adhesive joints at high loading rates is evaluated with the split Hopkinson bar technique using a pin-and-collar specimen. A commercially available cyanoacrylate adhesive(commonly termed an instantaneous adhesive)and two different adherend materials are used in the tests. The impact shear strength of the cyanoacrylate adhesive joints is determined from the applied shear stress history at failure initiation. Comparative shear tests at low loading rates are carried out on an Instron testing machine. The influences of loading rate, thickness of adhesive layer, and adherend materials on the shear strength of the cyanoacrylate adhesive joints are examined. The test results indicate that the shear strength increases significantly with increasing loading rate, and is greatly affected by both the adhesive layer thickness and adherend materials. It is shown that the shear strength increases to a maximum at an adhesive layer thickness of about 25 μm and subsequently decreases. The advantages and limitations of the technique are also discussed.

Determination of Impact Shear Strength of Adhesive Joints with the Split Hopkins Bar

Determination of Impact Shear Strength of Adhesive Joints with the Split Hopkins Bar

The effect of substrate roughness characteristics on wettability and on the mechanical properties of adhesive j oints loaded at high strain rates

This study describes the influence of the surface characteristics of a substrate on the joint strength in the case of a metal/polymer/metal sandwich. The objective was to evaluate the impact resistance of various adhesively bonded joints subjected to shear loading. The first part is devoted to the evaluation of the shear strength of adhesive joints at high strain rates using the Hopkinson pressure bar technique. The macroscopic approach enables us to compare different adhesive joints. The second part deals with the characterization of the substrate surface using roughness and wettability measurements, and this investigation shows the influence of substrate roughness characteristics on wettability and on the mechanical properties of adhesive joints. The micro-geometry of the substrate surface needs to be taken into account if one is interested in the influence of the roughness. We have tested adhesive joints that were made using different sheets under high strain rates. The surface of sheet was either untr...

木材接着接合部における強度評価の非破壊試験に関する基礎的実験 音波の伝ぱ時間による方法

In order to develop a nondestructive testing method applicable to manufacture more reliable adhesive wood components, fundamental experiments were performed. The strength of adhesive wood joints was evaluated by measuring the time of sound waves (stress waves, ultrasonics) propagating the part involving adhesive joints to guarantee the bonding strength more directly. The three types of experiments employed were as follows:(1) Measuring the propagation time of stress waves for the end joint and lap joint specimens in the curing process.(2) Measuring the propagation time of sound waves for the end joint specimens before and after gluing.(3) Mesuring the propagation time of ultrasonics in both thickness and width directions and the adhesive shear strength for the two-layer specimens.The results are summarized as follows:(1) Curing of adhesive joints could be evaluated by the propagation time of stress waves.(2) The change of propagation time before and after gluing indicates the difference in the state of adhesive joints.(3) The propagation time of ultrasonics in the thickness direction was effective for evaluating the shear strength of adhesive joints, but that in the width direction was not so effective.However, the shear strength can be evaluated more effective by combining the propagation time in these two directions.

木材接着接合の耐力評価表示法

More efficient use of construction adhesives as structural fasteners requires detailed knowledge on the behavior of adhesive joints between load-bearing building components under actual service conditions. As the strength of adhesive joint depends on the shear strength of wood as well as the strengths of adhesive and its bonded surfaces, both the strength of adhesive joint and the percentage of wood failure are provided as the test indicators. In this report, the relationship between the shear strength of adhesive joint and the percentage of wood failure was derived from the strength of wood and adhesive. The proposed schematic representation showing the distributions, of shear strength and of wood failure can be a powerful tool for evaluating how the strength changes with time or under accelerated aging, or which of the degrading factors is the major one. Based on observation of the shear test and the appearance of the fractured adhesive, interpretation of the results and recognition of the estimates under aging will become easier. A recent inspection of adhesive joints for glue-laminated timber after 6 years outdoor exposures shows that the rate of change in joint strength is attributable to the wood degradation and no adhesive failure occurs.

ＦＲＰ接着継手の疲労強度と耐久性

Fiber reinforced plastics (FRP) are increasingly being used in many areas as large-size construction or connecting structures. Adhesive constructions are applied for architectural parts, various kinds of water tanks, sewage purifiers, etc. But the reasons and methods of using the adhesive construction and the estimations of the life of these constructions have not been clarified yet.This paper concerns with the durability of adhesive joints of FRP by means of an accelerating exposure testing machine, and investigates the fatigue properties of adhesive joints. All of the adhesive joint specimens were treated with popular construction of glass roving and mat structure, and were bonded with epoxy-polyamides adhesives. Accelerating exposure hours for the periods of 0, 1500, 2000, 3000 and 4000 hours (4000 hours are about 6 month) were chosen, and properties of joint structures were examined for the static and the fatigue strengths. The static tests investigated were the average shear strength of adhesive joints and the bending strength of glass fiber reinforced plastics (GFRP) materials exposed to the accelerating exposure testing machine. Fatigue tests were carried out under the stress constant amplitude with tension-shear loads, and the fatigue strength as well as the stress-strain hysteresis loop were examined. According to the test of accelerating exposure, damages of adhesive joints were not detected for 3000 hours in either the static or the fatigue strength, but, with the exposure time over 3000 hours, the static and the fatigue strengths abruptly went down. Therefore, the accelerating exposure time leading to damages is believed to exist between 3000 to 4000 hours.It is revealed that adhesive structures are strengthened in the beginning of accelerating exposure and break down abruptly with the lapse of exposure time. Accordingly, the design of FRP adhesive joints must be generally taken into consideration of the durable hours of these structures and the fatigue behavior of abrupt fracture under the tension-shear loads.