Browsing by Author "Bane, M.D."
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- Comparative Failure Assessment of Single and Double Lap Joints with Varying Adhesive SystemsPublication . Nunes, S.L.S.; Campilho, Raul; Silva, F.J.G. da; Sousa, C.C.R.G. de; Fernandes, T.A.B.; Bane, M.D.; Silva, L.F.M. daJoining by adhesively bonded methods is being increasingly used in the design of mechanical structures, because of the significant benefits of this technique compared to the traditional ones. Commercial adhesives range from strong and brittle (e.g., Araldite® AV138) to less strong and ductile (e.g., Araldite® 2015). A new family of polyurethane adhesives combines high strength and ductility (e.g., Sikaforce® 7888). This work compares the tensile performance of the three aforementioned adhesive systems in single and double lap aluminum joints with varying values of overlap length (LO). A cohesive zone modeling (CZM) numerical analysis was carried out to analyze through-thickness normal and shear stresses in the adhesive layer, to study the CZM damage variable and to predict the joint strength. A comparison was also performed with simple analytical models. The stress and damage variable analyses helped in understanding the differences between adhesives in which pertains to the failure process and joint strength. The proposed work also enabled concluding that the CZM predictions are typically accurate, and which family of adhesives is more suited for each joint configuration, with clear advantage for the Sikaforce® 7888. As a result of this work, design guidelines were proposed for adhesively bonded joints.
- Effect of the size reduction on the bulk tensile and double cantilever beam specimens used in cohesive zone modelsPublication . Costa, M.; Viana, G.; Canto, C.; Silva, L.F.M. da; Bane, M.D.; Chaves, F.; Campilho, Raul; Fernandes, A.A.Cohesive zone elements used in finite element analysis are a reliable way to design and predict the behaviour of the joint. The characterisation of the traction separation law used in these models is done using tensile and fracture tests, and the parameters of such laws depend on humidity and temperature. Water diffusion tests are therefore necessary, which are dependent on specimen geometry, meaning a bigger specimen takes longer to fully saturate. To solve this problem and increase the efficiency of the ageing process, smaller tensile bulk and double cantilever beam (DCB) specimens are necessary. Another advantage of smaller DCB specimens is that they can be tested in smaller high-temperature chambers, where normal DCB specimens do not fit. Smaller geometries of the bulk tensile and DCB tests are analysed, and a proposed geometry for each test is shown to produce very satisfactory results, validating the use of these specimens.