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Authors
Abstract(s)
As juntas adesivas são uma alternativa viável para substituir ligações comuns como as mecânicas ou
soldadas, devido a diversas vantagens como a possibilidade de união de materiais de natureza
diferente, maior leveza, menores custos inerentes ao fabrico e ainda prevenção da corrosão galvânica
que pode ocorrer nas ligações entre dois materiais metálicos diferentes. A resistência de uma junta
depende, para um determinado tipo de solicitação imposta, da distribuição de tensões no interior da
junta. Por outro lado, a geometria das juntas, as propriedades mecânicas dos adesivos e os
componentes a ligar vão influenciar a distribuição de tensões. O carregamento nas camadas adesivas
de uma junta poderá induzir tensões de tração, compressão, corte, arrancamento ou clivagem, ou
ainda uma combinação de duas ou mais destas componentes.
O objetivo da presente dissertação é a caraterização completa de um adesivo estrutural de alta
ductilidade recentemente lançado no mercado (SikaPower®
-4720), para facilitar o projeto e
otimização de juntas adesivas ligadas com o mesmo. São quatro os ensaios a realizar: ensaios à tração
de provetes maciços (também denominados de bulk), ensaios ao corte com a geometria Thick
Adherend Shear Test, ensaios Double-Cantilever Beam e ainda ensaios End-Notched Flexure. Com
a realização dos ensaios referidos, são determinadas as propriedades essenciais à caraterização
mecânica e de fratura do adesivo.
Os resultados obtidos para cada ensaio resultaram em propriedades medidas com elevada
repetibilidade, da mesma maneira que se revelaram de acordo com os dados disponibilizados pelo
fabricante, sempre que estes estavam disponíveis.
Adhesive joints are a viable alternative to replace common connections such as mechanical or welded ones, due to several advantages such as the possibility of joining materials of different compositions, increased lightness, lower inherent production costs in addition to the prevention of galvanic corrosion that can occur in joining two different metallic materials. The strength of a joint depends on the stress distribution inside the joint, determined by the loading type. On the other hand, the geometry of the joint, the mechanical properties of the adhesives and the materials to join will influence the distribution of the tensions. The load in the adhesive layers of a joint can induce traction, compression, shear, peel or cleavage stresses, or even a combination of two or more of these constituents. The objective of this dissertation is the complete characterization of a structural adhesive of high ductility, recently launched on the market (SikaPower® -4720), in order to facilitate the design and optimisation of adhesive joints with this adhesive. With this purpose, four tests methods should be performed: tensile testing on bulk specimens, shear testing with Thick Adherend Shear Test joints, Double-Cantilever Beam tests and End-Notched Flexure tests. With these tests, the essential mechanical and fracture properties of the adhesive have been estimated. The results obtained for each test resulted in measured properties with high repeatability, in the same way as described with the available information given by the manufacturer, when it was made available.
Adhesive joints are a viable alternative to replace common connections such as mechanical or welded ones, due to several advantages such as the possibility of joining materials of different compositions, increased lightness, lower inherent production costs in addition to the prevention of galvanic corrosion that can occur in joining two different metallic materials. The strength of a joint depends on the stress distribution inside the joint, determined by the loading type. On the other hand, the geometry of the joint, the mechanical properties of the adhesives and the materials to join will influence the distribution of the tensions. The load in the adhesive layers of a joint can induce traction, compression, shear, peel or cleavage stresses, or even a combination of two or more of these constituents. The objective of this dissertation is the complete characterization of a structural adhesive of high ductility, recently launched on the market (SikaPower® -4720), in order to facilitate the design and optimisation of adhesive joints with this adhesive. With this purpose, four tests methods should be performed: tensile testing on bulk specimens, shear testing with Thick Adherend Shear Test joints, Double-Cantilever Beam tests and End-Notched Flexure tests. With these tests, the essential mechanical and fracture properties of the adhesive have been estimated. The results obtained for each test resulted in measured properties with high repeatability, in the same way as described with the available information given by the manufacturer, when it was made available.
Description
Keywords
Adesivo estrutural Junta adesiva Ductilidade Tenacidade à fratura Bulk Thick Adherend Double-Cantilever Beam End-Notched Flexure Structural adhesive Adhesive joint Ductility Fracture toughness ShearTest