Single-Lap Joints of Similar and Dissimilar Adherends Bonded with an Acrylic Adhesive

International Journal of Adhesion and Adhesives

Banea

Neto

et al. 2013

506

193

Adhesively-bonded joints are extensively used in several fields of engineering. Cohesive Zone Models (CZM) have been used for the strength prediction of adhesive joints, as an add-in to Finite Element (FE) analyses that allows simulation of damage growth, by consideration of energetic principles. A useful feature of CZM is that different shapes can be developed for the cohesive laws, depending on the nature of the material or interface to be simulated, allowing an accurate strength prediction. This work studies the influence of the CZM shape (triangular, exponential or trapezoidal) used to model a thin adhesive layer in single-lap adhesive joints, for an estimation of its influence on the strength prediction under different material conditions. By performing this study, guidelines are provided on the possibility to use a CZM shape that may not be the most suited for a particular adhesive, but that may be more straightforward to use/implement and have less convergence problems (e.g. triangular shaped CZM), thus attaining the solution faster. The overall results showed that joints bonded with ductile adhesives are highly influenced by the CZM shape, and that the trapezoidal shape fits best the experimental data. Moreover, the smaller is the overlap length (LO), the greater is the influence of the CZM shape. On the other hand, the influence of the CZM shape can be neglected whe n using brittle adhesives, without compromising too much the accuracy of the strength predictions.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modelling adhesive joints with cohesive zone models: effect of the cohesive law shape of the adhesive layer

International Journal of Adhesion and Adhesives

Banea

Neto

et al. 2013

506

193

“…More uniform stress fields, capability of fluid sealing, high fatigue resistance and the possibility to join different materials are other advantages of this technology. However, stress concentrations exist in bonded joints along the bond length owing to the gradual transfer of load between adherends and also the adherends rotation in the presence of asymmetric loads [2]. A large amount of works addresses the critical factors affecting the integrity of adhesive joints, such as the parent structure thickness, adhesive thickness, bonding length and geometric modifications that reduce stress concentrations [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Fracture toughness determination of adhesive and co-cured joints in natural fibre composites

Composites Part B: Engineering

Moura

Gonçalves

et al. 2013

a b s t r a c tAdhesive bonding has become more efficient in the last few decades due to the adhesives developments, granting higher strength and ductility. On the other hand, natural fibre composites have recently gained interest due to the low cost and density. It is therefore essential to predict the fracture behavior of joints between these materials, to assess the feasibility of joining or repairing with adhesives. In this work, the tensile fracture toughness (G c n ) of adhesive joints between natural fibre composites is studied, by bonding with a ductile adhesive and co-curing. Conventional methods to obtain G c n are used for the co-cured specimens, while for the adhesive within the bonded joint, the J-integral is considered. For the J-integral calculation, an optical measurement method is developed for the evaluation of the crack tip opening and adherends rotation at the crack tip during the test, supported by a Matlab sub-routine for the automated extraction of these quantities. As output of this work, an optical method that allows an easier and quicker extraction of the parameters to obtain G c n than the available methods is proposed (by the J-integral technique), and the fracture behaviour in tension of bonded and co-cured joints in jute-reinforced natural fibre composites is also provided for the subsequent strength prediction. Additionally, for the adhesively-bonded joints, the tensile cohesive law of the adhesive is derived by the direct method.

“…By comparing with Fig. 10 (tS ¼ 2 mm), an improvement of strength by increasing tS was found (5.5% for configuration 1), which can be explained by the increasing bending stiffness of the adherends and corresponding reduction of the peel effects [10]. In fact, the adherends opposed curvature resulting from the asymmetry of loading in single-lap joints results on a separation of the adherends at the overlap edges and compression in-between.…”

Section: Resultsmentioning

confidence: 97%

“…Finite Element simulations showed that shear peak stresses in the adhesive bond can be reduced by 20%. Pinto et al [10] showed by a Finite Element (FE) stress and failure analysis that increasing the stiffness of the adherends materials in single-lap joints leads to a reduction of the joint bending, which diminished stresses at the overlap edges and, consequently, increased the strength of the joints.…”

Section: Introductionmentioning

confidence: 99%

Effect of hole drilling at the overlap on the strength of single-lap joints

Pinto¹,

International Journal of Adhesion and Adhesives

Mendes³

et al. 2011

Bonded unions are gaining importance in many fields of manufacturing owing to a significant number of advantages to the traditional fastening, riveting, bolting and welding techniques. Between the available bonding configurations, the single-lap joint is the most commonly used and studied by the scientific community due to its simplicity, although it endures significant bending due to the non-collinear load path, which negatively affects its load bearing capabilities. The use of material or geometric changes in singlelap joints is widely documented in the literature to reduce this handicap, acting by reduction of peel and shear peak stresses at the damage initiation sites in structures or alterations of the failure mechanism emerging from local modifications. In this work, the effect of hole drilling at the overlap on the strength of single-lap joints was analyzed experimentally with two main purposes: (1) to check whether or not the anchorage effect of the adhesive within the holes is more preponderant than the stress concentrations near the holes, arising from the sharp edges, and modification of the joints straining behaviour (strength improvement or reduction, respectively) and (2) picturing a real scenario on which the components to be bonded are modified by some external factor (e.g. retrofitting of decaying/old-fashioned fastened unions). Tests were made with two adhesives (a brittle and a ductile one) varying the adherend thickness and the number, layout and diameter of the holes. Experimental testing showed that the joints strength never increases from the un-modified condition, showing a varying degree of weakening, depending on the selected adhesive and hole drilling configuration.