This article was published in the journal, International Journal of Adhesion & Adhesives [© Elsevier] and the definitive version is available at: http://www.sciencedirect.com/science/journal/01437496The single lap joint is the most studied type of adhesive joint in the literature. However, the joint strength prediction of such joints is still a controversial issue as it involves a lot of factors that are difficult to quantify such as the overlap length, the yielding of the adherend, the plasticity of the adhesive and the bondline thickness. The most complicated case is that where the adhesive is brittle and the overlap long. In any case, there is still a problem that is even more difficult to take into account which is the durability. There is a lack of experimental data and design criteria when the joint is subjected to high, low or variable temperature and/or humidity. The objective of this work is to carry out and quantify the various variables affecting the strength of single lap joints in long term, especially the effect of the surface preparation. The Taguchi method is used to decrease the number of experimental tests. The effect of material, geometry, surface treatment and environment is studied and it is shown that the main effect is that of the overlap length. In order to quantify the influence of the adhesive (toughness and thickness), the adherend (yield strength and thickness), the overlap, the test speed, the surface preparation and durability on the lap shear strength, the experimental design technique of Taguchi was used in the present study. An experimental matrix of eighteen tests was designed and each test was repeated three times. The influence of the eight previously-mentioned variables could be assessed using the statistical software Statview®. In this paper a simple predictive equation is proposed for the design of single lap joints

This work presents a review of several investigations on the topic of adhesive bonding at high and low temperatures. Durability and strength at extreme temperatures have always been a major limitation of adhesives that, given their polymeric nature, exhibit substantial degradation at temperatures where other structural materials (such as metals for example) have minute changes in mechanical properties. However, due to the inherent advantages of bonding, there is a large and continued effort aiming to improve the temperature resistance of adhesive joints, and this effort has been spread among the various topics that are discussed in this review. These topics include adhesive shrinkage and thermal expansion, adhesive properties, joint geometry optimization, and design techniques, among others. The findings of these research efforts have all found use in practical applications, helping to solve complex problems in a variety of high-tech industries where there is a constant need to produce light and strong components that can withstand large temperature gradients. Therefore, the final sections of this work include a discussion on two specific application areas that demonstrate the strict demands that extreme temperature use imposes on adhesive joints and the methods used to improve their performance.

This paper describes the influence of the curing temperature on the physical and mechanical properties of three structural adhesives. This work was undertaken to improve the understanding of the effect of curing temperature in the glass transition temperature, T _g , and stiffness of epoxy adhesives. The mechanical properties (Young's modulus and yield strength) of the adhesives were measured in bulk specimens. T _g was measured by a dynamic mechanical analysis using an in-house developed apparatus. The curing process was the same for all tests, consisting of a curing stage followed by a post cure stage. The initial stage was performed at different temperatures. T _g and the mechanical properties was found to vary as a function of the cure temperature of the adhesive. When cured below the cure temperature, T _cure , at which the T _g of the fully cured network, T _{g ∞}, is achieved, the strength and stiffness of the adhesive increase as the cure temperature increases and the T _g is higher than the cure temperature. When cured above the T _cure at which the T _{g ∞} is achieved, the strength and stiffness decrease as the cure temperature increases and the T _g is higher than the cure temperature.