PSI - Issue 41

A.E.S. Pinheiro et al. / Procedia Structural Integrity 41 (2022) 60–71 Pinheiro et al. / Structural Integrity Procedia 00 (2019) 000 – 000

61

2

requires connections between its components, using more traditional methods such as welding, brazing, mechanical and riveted connections or, more recently, by adhesive bonding. Adhesive joints have been increasingly applied in various industries such as transport, as due to numerous advantages, making it possible to maintain or improve structural strength and reduce fuel consumption. The main advantages of adhesive bonding are the reduced weight of the connection, a more uniform stress distribution and the possibility to join different materials (Adams 2005). The most applied adhesive joint configuration is the single-lap joint, due to its simplicity in manufacturing, its application to thin adherends and the predominant τ xy stress loading in the adhesive layer (Heidarpour et al. 2018). The main disadvantage of this joint configuration is the misalignment between the adherends leading to a bending moment in the joint and originating σ y stresses at the overlap edges (Petrie 2000). In order to mitigate this effect, other configurations can be used such as double-lap joints (Wei et al. 2022), lap joints with chamfers (Belingardi et al. 2002), among others. In these joint configurations the effects of bending are considerably lower, but the manufacturing process is more complex and time consuming (Petrie 2000). Another commonly used adhesive joint configuration is the single-strap, in this configuration the adherends are aligned, and it is usually applied when it is difficult to use the overlap joints because of the adherends’ thickness. Under bending loads this joint configuration is mainly subject ed to σ y stresses. An upgrade version of the previous configuration is the double-strap joint that performs well under bending and presents a better stress distribution across the bonding area (Petrie 2000). The butt adhesive joint configuration is the simplest one to manufacture since the bonding of the two adherends is performed at the cross section tops. However, this configuration is sensitive to bending loads because the adhesive is mainly subjected to cleavage stresses. This configuration is avoided in real applications, although it is useful as a test procedure to evaluate the joint performance. In corner joints, the adherends are usually oriented perpendicularly to each other. However, it is also possible to use layouts with different orientations. Under tensile loads, the corner joint reveals less strength, but when compressive loads are applied the joint barely deforms, except in the event of adherend buckling. When the corner joints have two perpendicular angles, they are called as T-joints (Petrie 2000, da Silva et al. 2018). The main concepts of adhesive joint configurations applied to flat adherends are also valid for tubular adhesive joints. Tubular joints present elevated strength to bending loads, have a larger overlap area than other types of joints and enable the assembly of lightweight and stiff structures. However, most tubular joint configurations require adherend milling operations (Eusébio and Campilho 2019). Guess et al. (1995) experimentally and numerically evaluated the effects of tensile, compression and bending loads in tubular overlap joints. Based on their study the authors concluded that the calculated surface strains are in good agreement with the ones obtained experimentally and that the joint failure takes place in the region of the calculated peak σ y stresses. Tubular chamfer joints were first analyzed by Hashim et al. (1998) in the late 1990s with the aim of optimizing the joints’ chamfer shape as well as their strength. The authors concluded that the chamfer joint presents a good coupling capacity between the adherends, allowing an easier manufacture process. Das and Pradhan (2011) investigated external strap tubular adhesive joints with composite adherends by a finite element method (FEM) numerical analysis. Failure was assessed by the quadratic failure criterion for the adhesive and the Tsai – Wu coupled stress criterion for the tube-adhesive and adhesive-patch interfaces. The goal was to analyze the failure onset and growth in the adhesive joint seeking to improve load-bearing capability and promote improved (more uniform) stress distributions in the bonded region. The authors concluded that adhesion failures begin at the free ends of the tube-adhesive interfaces followed by self-similar manner propagation under shear mode. Sawa et al. (1987) studied tubular butt adhesive joints subjected to torsion loads. From the analysis it was found that the tubular joint has a superior torsional resistance if the bond is placed near to the outer diameter of the tubes comparatively to the inner region of the cross section. The static and dynamic strength of tubular butt joints was experimentally investigated by Sato and Ikegami (1999). In the first phase, tensile and torsion loads were applied with a dynamic loading scheme that contemplated variable amplitude and frequency over time and, subsequently, a static load was applied. The authors concluded that the tubular butt adhesive joint presented a higher strength under dynamic loading when compared to static loading for all load types. The pioneers in developing strength prediction methodologies for adhesive joints were Volkersen (1938) and Goland and Reissner (1944). Their methods are based on analytical formulations with closed-form expressions, which ignore material and geometric specifications. The purposed methodologies showed to be inaccurate when applied to complex geometries. The first work introducing FEM analyses for the strength prediction of adhesive joints was developed by Adams and Peppiatt (1974). The authors formulated a method that relies on the knowledge of the stress distribution and the application of a proper continuum-mechanics failure criterion. A satisfactory agreement was found