Effect of adhesive thickness on the strength of steel-composite joints aged in wet environment (original) (raw)
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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 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.
The Bulletin of the Polytechnic Institute of Jassy, Construction. Architecture Section, 2018
One of the most recent development directions of composite materials that are used in the civil engineering industry consists in applying these materials in the strengthening applications of metallic elements. This paper presents some particularities of the failure process for adhesively bonded joints between carbon fibre reinforced polymers (CFRP) composite products and steel elements. The specific outcomes presented in this paper are part of the results obtained by carrying out a complex experimental program at the Faculty of Civil Engineering and Building Services of Iaşi, which focused on the bond behaviour between CFRP composite products and steel.
Hygrothermal Durability of Adhesively Bonded FRP/Steel Joints
Proceedings of International Structural Engineering and Construction
The use of fiber reinforce polymer, FRP, bonding to strengthen and repair deteriorated steel structures is increasing owing to its unique advantages over traditional strengthening and repair techniques. However, the lack of knowledge regarding environmental durability of adhesively bonded FRP/steel joints still hinders the widespread application of this method in steel structures. A number of studies have reported significant degradation of mechanical properties of these joints in hot and wet environments. In addition to that, the mechanisms of failure have been observed empirically to change from cohesive failure in the adhesive to apparent interfacial failure with increasing amount of moisture. This study presents the results of an experimental and numerical investigation to predict the mechanical behavior of FRP/steel joints after hygrothermal aging. First, moisture diffusion kinetics and mechanical degradation of a two-part commercially available epoxy adhesive and Carbon FRP ma...
Durability of steel-CFRP structural adhesive joints with polyurethane adhesives
Composites Part B: Engineering, 2018
The use of reinforcing materials in steel structures is very widespread today because this combination is capable of bringing great improvements to this type of structures. In this work, a steel-CFRP (carbon fiber reinforced polymer) adhesive joint is proposed, trying to combine the good properties of both materials. Two structural polyurethane adhesives, one conventional and another hybrid, are selected to develop the joint due to the good properties of this material against external environmental agents and the high loads that are capable of resisting. The objective is to verify the suitability of this type of joints for structural applications in aggressive environments. For this purpose shear tests are carried out on specimens subjected to different exposure times in an aggressive environment, evaluating how their mechanical properties vary. Reliability studies are developed using a simplified model of the Weibull distribution, obtaining the distribution of failures of the joints. Microscopy techniques (Scanning Electron Microscope and optical microscope) are used to evaluate the failures of the studied specimens. The reliability of
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...
Effect of moisture on the adhesion of CFRP-to-steel bonded joints using peel tests
Journal of the Brazilian Society of Mechanical Sciences and Engineering
In this work, an experimental study has been carried out to evaluate the effect of salt water condition on the long-term adhesion of composite-to-metal bonded joints using peel tests. A new test configuration is tested via fully and partially immersed specimens with 500 mm length. Fracture surfaces of non-aged samples exhibited a cohesive failure within the adhesive layer, which indicates a good adhesion of the joint. Results revealed a significant difference in the interface adhesion between aged and non-aged condition after 150 days of immersion. Partially immersed specimens allow to evaluate the adhesion performance of the joint under dry and wet condition in single specimen using a simple peel test.
Advances in Science and Technology Research Journal
The following paper analyses selected problems regarding the impact of technological parameters and the type of adherend material on the strength of adhesive-bonded steel sheet joints. The subject of the test was a single-lap adhesive joint of S235JR steel sheet. Joints were formed on two types of substrates: with or without corrosion products on the surface. The surface of steel sheet adherends was pre-treated with three cleaning solutions: acetone, Wiko industrial degreasing agent and Cortanin F anti-corrosion agent, depending on the state of the surface. Adhesive joints were formed with Epidian 53/ET/100:15 epoxy adhesive. The formed joints were subjected to one of three ageing variants: 14 days, two months and 3 months, which were followed by destructive testing to determine the shear strength of joints. The analysis of results obtained in the tests indicates that the strength performance of adhesive joints of corrosion-free adherends was characterised by higher values than in corroded steel sheets, regardless of ageing time.
Composites Part B: Engineering
This paper investigates the effects of environmental ageing on the mechanical response of adhesively bonded double-lap shear joints made of steel and CFRP or GFRP adherents. One hundred and ninety-two specimens, 84 joints and 108 material coupons, were aged for up to three years in various environments including (i) immersion in distilled water at 20 C and 45 C, (ii) immersion in de-icing salt solution at 20 C and 45 C and (iii) exposure to 95% relative humidity at 45 C. In general, immersion at 45 C resulted in noticeably greater strength reductions at both material and joint level. While the strength and stiffness of the joints made of GFRP material underwent significant reductions, the CFRP/steel joints were affected to a considerably smaller degree. FE simulations showed the impact of the permeability of FRP adherents and moisture distribution at the FRP/adhesive interface on the integrity and strength of the joints. The joint-level results are compared with the most relevant durability data in the literature.
Adhesively bonded joints in composite materials: An overview
Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications, 2009
A review of the investigations that have been made on adhesively bonded joints of fibre-reinforced plastic (FRP) composite structures (single skin and sandwich construction) is presented. The effects of surface preparation, joint configuration, adhesive properties, and environmental factors on the joint behaviour are described briefly for adhesively bonded FRP composite structures. The analytical and numerical methods of stress analysis required before failure prediction are discussed. The numerical approaches cover both linear and non-linear models. Several methods that have been used to predict failure in bonded joints are described. There is no general agreement about the method that should be used to predict failure since the failure strength and modes are different according to the various bonding methods and parameters, but progressive damage models are quite promising since important aspects of the joint behaviour can be modelled by using this approach. However, a lack of rel...