Effect of saline environment on properties of adhesive joints (original) (raw)
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Procedia Engineering, 2013
Structural adhesive joints are adequate for joining aluminum with composite material (automotive, aeronautic, etc.). However, in many occasions, these adhesive joints are subjected to very adverse service conditions. This way, depending where they are, they must resist great humidity, oil projections, high temperatures, etc. For this cause, an appropriate operation of these adhesive joints requires know its behavior under these conditions. In line with this objective, present work analyzes the degradation that adhesive joints of composite material and aluminum experiences when they are immersed in water or motor oil. Also, the loss of mechanical properties originated by this degradation has been evaluated quantitatively by flexion tests.
International Journal of Engineering Sciences, 2019
The objective of research work is to establish the influence of environmental factors such as moisture and temperature on the shear properties of metal and polymer joints. The specimens of metal and polymer joints were prepared with aluminium plate and glass fibre reinforced plastics. Here three types of resins were used for joining the metal and polymer composites viz. epoxy vinyl ester and polyester. The joint specimens were exposed to 80 C temperature and relative humidity of 90% for 25 days in environmental chamber. The single and double shear strength of the joints for ascast and hygrothermal exposed specimens are investigated. The results showed that the strength of hydrothermal specimens decreased about 25%, 18% and 33% for epoxy, vinyl ester and polymer adhesive joints respectively. The result also shows that vinyl ester joints exhibit lower water absorption and property degradation of the joints.
Effect of water absorption on the adhesive damage in bonded composite repair of aircraft structures
2014
In this study, the mechanical properties of the aged adhesive Adekit A140 epoxy were used in a finite element model to evaluate the effect of water absorption on the adhesive damage in bonded composite repair of aircraft structures. The damage zone theory was implemented in the finite element code in order to achieve this objective. In addition, the effect of the water absorption, by the adhesive, on the repair efficiency was analyzed by computing the stress intensity factor at the crack tip. The obtained results show that, when the water absorption increases the adhesive loses its rigidity, which reduces the repair durability. Besides, it leads to the increase of the stress intensity factor at the crack tip indicating a reduction in the repair efficiency.
Non-Fickian Absorption Characteristics of Adhesive Joints: Capillary Effects and Residual Properties
International Journal of Integrated Engineering
Mechanical performance of polymer-based adhesive joints is generally susceptible to moisture absorption. This study quantifies the effects of moisture content on the strength, stiffness, and energy properties of adhesive bonded joints. For this purpose, moisture absorption characteristics of structural adhesive joints (Araldite 2015) with different thicknesses (0.5, 1.0, and 1.5 mm) were firstly established under accelerated aging condition (deionized water at 60 o C). A thickness-dependent non-Fickian moisture absorption model was then used to characterize the moisture absorption of the adhesive joints. Results suggested that the moisture absorption of the adhesive joints was governed by the capillary action. Subsequently, adhesive joints with aluminum 6061 adherent and 0.5 mm-thick Araldite 2015 adhesive compound were subjected to dry, 0.1, 0.15, 0.18, and 0.2 pct of moisture content. The specimens were tested in shear and tension loadings at 1 mm/min. The resulting variations in the mechanical properties were fitted using a residual property model. It was noticed that all properties degraded upon moisture attack. For strength and energy properties, the degradation was more severe in tension. As for the stiffness, the decrease in the property was similar in both tensile and shear. The results from this study showed that moisture attack is an important aspect to be considered when designing for the service lifetime of adhesive bonded structures.
Progress in Organic Coatings, 1988
The influence of a thin adhesive layer (AL) of a polymer on the wet adhesion of an epoxy coating on an aluminium substrate has been studied by the peel and tape test method. It is shown that thin layers considerably improve the stability of adhesive joints in the presence of water. The mechanism of this improvement and the mechanical properties required for such thin layers are discussed. Some experimental evidence for improved wet adhesion of polymer binders to an aluminium support is presented and the mechanism explained. These results on interfacial processes contribute to a better understanding of the mechanism of adhesion.
IOP Conf. Series: Materials Science and Engineering 532 (2019) 012007, 2019
This paper presents the effect of adhesive layer thickness on the static strength of adhesively bonded steel-glass fiber-reinforced unsaturated polyester resin (GFRP) lap joints after being aged in water at a temperature of 60 o C for 15 days. The adhesive thickness was varied from 0.1 mm to 0.5 mm. It was found that for the dry joints, the static strength increased with the increase of adhesive thickness. However, in wet condition, water really had a significant detrimental effect on the strength of the joints, as most of the strengths of wet joints were much lower than those of the dry joints. In dry condition, mode of failure changed from interfacial (at the adhesive thickness of 0.1 mm) to mix failure; however, for the wet joints; most of failures were at the interface of adhesive/steel. 1. Introduction Nowadays, adhesively bonded metal-composites joints gain more applications in transportation industry in order to develop lightweight vehicles. Other sectors used adhesively bonded joints technology, mainly for strengthening steel-made bridge structures, concrete and wood structures. The drawback in making use of adhesively bonded joints is the capability of the adhesive to absorb water from the surrounding environment. It is well known that the absorbed water has deleterious effect on the strength of the adhesive joints; therefore, designing an adhesive joint in those applications become attractive researches, considering the effect of adhesive thickness, type of adhesive and substrate, and type of environment. Theoretically, (i.e. Goland-Reissner's and Volkersen's theories) an adhesively bonded joint strength increased with the increase of adhesive thickness [1], however experimentally, most literature reported that the joint strength decreased with the increase of adhesive thickness [2-8]. To obtain a high joint strength, the adhesive thickness should be thin enough, in the range of 0.1-0.5 mm [9]; however, it depended on the adhesive type. For very ductile adhesive, such as polyurethane, the adhesive thickness between 0.5 mm and 1 mm gave the optimum strength for aluminium joints [4]. For many structural adhesives, the optimum adhesive thickness was in the range of 0.1-0.2 mm [9]. Water can enter into the adhesive joint through several mechanisms; diffusing into the bulk adhesive, wicking into the interface, capillary action into micro voids and cracks, and diffusing into permeable substrate before reaching the adhesive layer [10]. The absorbed water then degrades the mechanical properties of adhesive and affects the interface of adhesive/substrate. Often during aging,
Engineering Fracture Mechanics, 2011
This paper presents a methodology to predict the strength of adhesive joints under variable moisture conditions. The moisture uptake in adhesive joints was determined using a history dependent moisture prediction methodology where diffusion coefficients were based on experimental cyclic moisture uptake of bulk adhesive samples. The predicted moisture concentrations and moisture diffusion history were used in a structural analysis with a cohesive zone model to predict damage and failure of the joints. A moisture concentration and moisture history dependent bilinear cohesive zone law was used. The methodology was used to determine the damage and failure in aluminium alloy -epoxy adhesive single lap joints, conditioned at 50°C and good predictions of failure load were observed. The damage in the adhesive joints decreased the load carrying capacity before reaching the failure load and a nonlinear relationship between the load and displacement was observed. Changes in crack initiation and crack propagation were also observed between different types of joints. The presented methodology is generic and may be applied to different types of adhesive joint and adhesive.
Effect of Humidity on The Fatigue Behaviour of Adhesively Bonded Aluminium Joints
Latin American Journal of Solids and Structures
The present work focuses on the effects of water degradation on the fatigue behaviour of adhesive joints bonded with aluminium adherends. The objective of this study is to measure the influence that humidity has on the fatigue crack growth velocity of two distinct adhesives characterized using the Paris Law, using double cantilever beam (DCB) specimens in unaged and various aged conditions loaded in mode I in order to understand the influence that water content has on the Paris Law constants. It was found that the slope of the Paris Law curve is not heavily changed with the presence of water, but a shift in the curves does occur, generally resulting in a crack initiating at a lower threshold than in the unaged adhesive. Based on this behaviour, it can be concluded that an increase in water content reduces the fatigue joint strength and lifespan of adhesive joints bonded with the studied adhesives.
Effect of adhesive thickness on the strength of steel-composite joints aged in wet environment
IOP Conference Series: Materials Science and Engineering, 2019
This paper presents the effect of adhesive layer thickness on the static strength of adhesively bonded steel-glass fiber-reinforced unsaturated polyester resin (GFRP) lap joints after being aged in water at a temperature of 60°C for 15 days. The adhesive thickness was varied from 0.1 mm to 0.5 mm. It was found that for the dry joints, the static strength increased with the increase of adhesive thickness. However, in wet condition, water really had a significant detrimental effect on the strength of the joints, as most of the strengths of wet joints were much lower than those of the dry joints. In dry condition, mode of failure changed from interfacial (at the adhesive thickness of 0.1 mm) to mix failure; however, for the wet joints; most of failures were at the interface of adhesive/steel.
Study on Influence of Moisture Absorption Strength of Adhesive T-Joint
Applied Mechanics and Materials, 2014
Adhesive is commonly required to fulfil an explicit mechanical role where mechanical properties can affect their performance. The mechanical properties of adhesive are known to vary with moisture content. This paper presents a study of moisture absorption epoxy adhesive joint as alternative to welding joint in urea granulator chamber. Welding joint requires high skills to avoid joint failure. In particular, bulk specimens were exposed to three humidity conditions, namely, 80ᴼC, 90ᴼC, and 100ᴼC at a constant time immersion of 15 minutes in water. Compression test revealed that Young modulus decreased with increasing water temperature. Moisture condition has some effect on the strength of the adhesive bonding with certain thickness. 1.0 mm of adhesive thickness provides the highest value failure load for every thickness and conditional water temperature. Experimental result indicated that failure load of adhesive T-joint at room and 90ᴼC water temperature give relatively high value of strength if compared to water temperature at 80ᴼC and 100ᴼC.