Durability Of Adhesive Joints Research Articles

Durability of adhesive-bonded joints employing organosilane coupling agents

One of the major problem areas that continues to confront the use of structural adhesives in engineering applications concerns the effects of atmospheric moisture which, under certain circumstances, can seriously impede the load-bearing capacity of a bonded component. Various approaches can be used in an attempt to alleviate moisture-related problems, one being the use of organosilanes, particularly when employed as pre-bond primers. Since experience has shown that organosilanes perform best in dilute solution, a great deal of the research conducted in the authors' laboratory, much of which is presented here, has been concerned with the study of organosilane solutions as primers. Experimental parameters shown to be of importance include the nature of the solvent employed, the solution age and pH, and the conditions under which the silane film is subsequently dried. The results suggest that failure to study experimental parameters such as these could provide no significant improvements in adhesive joint durability and thus provide a misleading impression of the beneficial qualities of organosilane coupling agents.

Influence of water on the cleavage of adhesive joints

Abstract Adhesive joints are easily cleaved by a wedge. The length of the crack that is produced characterizes the resistance to fracture, R , of the adhesive. It is known that the long-term resistance to fracture of an adhesive-bonded joint is affected by a humid environment. An attempt has been made to quantify this process by the study of cleavage in liquid water and the evolution of cleaved joints both in liquid water and water vapour. It was observed that water (liquid or vapour) as well as the water content of the adhesive lowers R and induces an apparently interfacial failure on polished surfaces. In the long-term, both liquid water and high humidity cause the debonding of cleaved joints. In effect there is a threshold of humidity at which water vapour accelerates the cracks. These observations are interpreted as an indication of two different processes in the debonding of adhesives, one occurring at high speed characterizes the initial strength of the joint, the other at low speed governs the durability of adhesive joints.

Adhesives Technology Handbook

Comprehensive technical treatment of the field of structural adhesive bonding. The data categories include: Definition of Terms; Joint Design and Design Criteria; Surface Preparation of Adherends; Adhesive Types and Their Properties and Applications; Adhesives for Specific Adherends; The Adhesive Bonding Process; Solvent Cementing of Plastics; Effects of Environment on Durability of Adhesive Joints; Quality Control; Test Methods; Standard Specifications and Test Methods (235); Applications of Adhesive Bonding; Appendix -- Sources of Information. -- AATA

Bonding and Failure Mechanisms in Aluminium Alloy Adhesive Joints

Abstract X-ray photoelectron spectroscopy and scanning electron microscopy have been used to investigate the surface chemistry of an aluminium-alloy which has been pretreated by various industrial methods commonly employed prior to adhesive bonding. The fracture surfaces of butt joints, consisting of the pretreated alloy bonded with an epoxy adhesive, have also been studied. The analyses have been conducted before and after exposure of the specimens to water, the main hostile environment that structural adhesive joints usually encounter. It is suggested that the concentration of magnesium, in the form of magnesium oxide, on the pretreated aluminium-alloy surface may be an important factor in influencing the durability of adhesive joints.

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.

Environmental aspects of adhesion and adhesive joint strength

AbstractWe have outlined a theory which considers the durability of adhesive joints in the presence of a hostile environment. The approach is basically the Griffith theory modified for the presence of liquids. Two main conditions for spontaneous delamination of a composite appear to be immiscibility of the liquid in the environment with the members of the composite and complete interaction of the liquid (in a surface‐chemical sense) with one or more members of the composite. In the absence of chemisorption and interdiffusion in an A‐B composite, we find that (σfL/σf)2 = WABL/WAB, where σf is the critical stress to failure, WAB is the work of adhesion, and the superscript L refers to the presence of a liquid phase. When the liquid (L) interacts, in a surface‐chemical sense, with the composite, we have WAB > WABL, and σfL < σf. To illustrate the main features of the theory, composites are prepared whose interfacial tensions have been modified by the presence of an adsorbed monolayer of a fatty acid. In this instance, the interfacial tensions are changed so that WAB ≈ WABL and σfL ≈ σf. The composite then becomes more stable under an applied stress in the presence of an environment of high relative humidity.

Surface roughness and rheological properties of adhesives as factors determining optimal thickness of glue line

The effect of the thickness of the glue line on the bond strength of construction materials is examined and the dependence of the optimal thickness of the glue line on surface roughness and glue viscosity is shown. The effect of surface roughness on strength and durability of adhesive joints is explained on the basis of a molecular mechanism of interaction of the glue with the surface roughnesses and an approximate expression is derived for the depth of penetration of the glue into microcavities of the surface as a function of the geometric parameters of the microcavities, specific pressure, and surface tension of the interface with the air.