Non-Fickian Absorption Characteristics of Adhesive Joints: Capillary Effects and Residual Properties (original) (raw)
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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.
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,
International Journal of Adhesion and Adhesives, 2013
The aim of this research is to investigate the effect of moisture on the static response of adhesively bonded monolithic single lap joints and laminated doublers loaded in bending. All joints were made of aluminium alloy Al 2024-T3 bonded using epoxy film adhesive FM 73M OST. The joints were aged in deionised water at a temperature of 50 °C for up to 2 years exposure. The use of different widths of specimen (5 mm for monolithic single lap joints and 15 mm for laminated doublers) allowed both full and partial saturation of the adhesive layer. The bulk adhesive has been characterised to obtain the coefficient of moisture diffusion, the coefficient of thermal and moisture expansion and the moisture dependent mechanical properties. The testing results showed that the mechanical properties degraded in a linear way with the moisture content. The residual strength after exposure decreased with increasing moisture content (exposure time) and tended to level off towards saturation. The damag...
Moisture Absorption Analysis of High Performance Polyimide Adhesive
The high temperature resistant polymers and metal composites are used widely in aviation, space, automotive and electronics industry. The high temperature resistant polymers and metals are joined together using high temperature adhesives. Polyimide and epoxy adhesives that can withstand high temperature (200 °C-300 °C) are commonly used for joining high temperature metals and polymers. The performance of adhesively bonded metals and polymers depends upon physical properties of these high temperature adhesives. The physical properties like modulus, Tg. coefficient of thermal expansion (CTE) etc., are affected by external factors such as force, temperature, humidity etc. The external factors play a vital role in the adhesive bond strength and the durability of bond between metal and polymer. In this investigation moisture absorption analysis of polyimide adhesive is performed using Q5000 moisture absorption analyzer. The moisture absorption data of polyimide at different temperatures and humidity level is obtained. Further, the moisture absorption data is fitted to well known Fickian-fit model to determine the diffusion coefficient (D) and saturated moisture gain Msat. Diffusion coefficient (D) and Msat of polyimide and epoxy adhesive are calculated at different temperature and different humidity level. It is observed that diffusion coefficient changes with the change in temperature and humidity level. The diffusion coefficient (D) and M sat data are used in Fick's second law of diffusion to estimate the time needed for preconditioning of the adhesively bonded titanium samples in humidity chamber at elevated temperature and higher moisture level. After preconditioning of adhesively bonded Titanium samples in moisture chamber for estimated time, samples will be subjected to lap shear tensile test to study the effect of these elevated conditions on adhesive bond strength.
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.
2021
This study focuses on evaluating the impact of aluminum adhesive joints as a function of temperature and moisture, in an effort to understand how these conditions affect their mechanical properties and behavior. After preparing the required specimens (using two different adhesives and adherend thicknesses), several tests have been made in order to determine these properties and compare their values to the predictions made using analytical methods. These tests were repeated with several distinct combinations of temperatures and moisture levels so that the effect of these properties can be properly interpreted. It was observed that higher temperatures strongly increase the ductility of the adhesive but mixed with moisture this can degrade them. Moisture can increase the energy absorbed through increased plastic deformation of the adhesive and improve behaviour at low temperatures.
Determination of the fracture envelope of an adhesive joint as a function of moisture
Materialwissenschaft und Werkstofftechnik
Adhesively joints are increasingly being used in aerospace, automotive and maritime industries. The use of this type of joining provides some advantages such as reduction in weight and cost. However, adhesive joints in transportation industry may be exposed to aggressive environments such as high humidity during their service life. A particular issue with the reliability of adhesive joints is the presence of cracks and flaws. Fracture mechanics tests for adhesive joints provide relevant mechanical properties to determine the adhesive toughness and play an important role in design process. This research aims to determine the fracture toughness of aluminum/adhesive/aluminum joints under pure mode I, pure mode II and mixed mode loadings. The fracture characterization of adhesively joints was performed when these specimens were submitted to mixed mode loadings and pure modes (shear and opening). The experimental tests Double Cantilever Beam (DCB) and End-Notched Flexure (ENF) were also done in order to assess the fracture toughness in Paiva for the help and advice while developing this thesis. A special thanks to Joana, Daniel and Rodrigo for the friendship and for being always by my side during this semester. And finally, all my family and friends for the support when I needed the most.
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.
Effect of saline environment on properties of adhesive joints
Water diffusion into composite adhesive joints was experimentally studied by means of gravimetric measurements in bond specimens. The main parameters controlling the diffusion in the bond components were obtained from water uptake experiments carried out in bulk specimens of fiber-reinforced composite and epoxy adhesive. The diffusion of water in bonds is a complex mechanism due to the heterogeneous microstructure of the composite and its interface with the adhesive. This process was simulated through micro scale models which represent the microstructure of the composite and of the adhesive joint Structural adhesive joints are adequate for joining aluminum with nearly constant. In terms of fatigue strength,for105 cycles, a decrease about 25%and 39%occurred in specimens immersed during