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Abstract(s)
Nesta nova fase industrial, e com desenvolvimento de novos materiais, tem-se observado um incremento gradual na substituição de componentes, que veio alertar para outra situação que, na perspetiva global de um projeto, não é menos importante - a união dos vários componentes. No remoto e próximo passado, a união referida era efetuada por componentes mecânicos (rebites ou parafusos) ou por soldadura, mas estes métodos apresentam alguns inconvenientes, tais como aumento do peso, problemas corrosivos, concentrações de cargas nas zonas unidas e risco de fissuração. Devido a estes inconvenientes, surge a solução de ligação adesiva dos componentes. No entanto, para a aplicação desta técnica e para a utilização de ferramentas de cálculo que permitam ao projetista dimensionar estruturas adesivas, é fundamental o conhecimento das propriedades mecânicas e de fratura mais relevantes dos adesivos a usar. Este estudo apresenta a caracterização de um adesivo estrutural que foi lançado recentemente no mercado, pelo que é fundamental caracterizá-lo para efeito de projeto de estruturas adesivas. Para tal, é necessário realizar ensaios de tração com provetes bulk para se obter propriedades mecânicas tais como o módulo de Young (E), a tensão de cedência (y), a tensão de rotura à tração (f) e a deformação de rotura à tração (f). É também realizado o ensaio Thick Adherend Shear Test (TAST), que tem como finalidade caracterizar as propriedades mecânicas ao corte, e permite obter os resultados do módulo de corte (G), tensão de cedência ao corte (𝜏y), tensão de rotura ao corte (𝜏max), e deformação de rotura ao corte (). Através do ensaio Double-Cantilever Beam (DCB) calcula-se a taxa crítica de libertação de energia de deformação em modo I (GIC) pelos métodos Compliance Calibration Method (CCM), Corrected Beam Theory (CBT) e Compliance-Based Beam Method (CBBM). Por último, no ensaio End-Notched Flexure (ENF) calcula-se a taxa crítica de libertação de energia de deformação em modo II (GIIC) pelos métodos Compliance Calibration Method (CCM), Corrected Beam Theory (CBT) e Compliance-Based Beam Method (CBBM). Após a realização dos ensaios referidos e análise dos dados obtidos, verificou-se que existe uma boa repetibilidade entre provetes do mesmo ensaio e uma convergência de valores do adesivo caracterizado em laboratório com os valores do fabricante.
In this new industrial era, and with the development of new materials, there has been a gradual increase in the replacement of components, which has come to warn of another situation that, in the global perspective of a design project, is not less important - joining the various components. In the remote and near past, joining was accomplished by mechanical components (rivets or screws) or by welding, but these methods have some drawbacks, such as increased weight, corrosive problems, loads concentrations in the joined areas and risk of cracking. Due to these drawbacks, the adhesive bonding solution for components appears. However, for the application of this technique and for the use of design tools that enable the designer to design adhesive structures, it is essential to know the most relevant mechanical and fracture properties of the adhesives to be used. This study presents the characterization of a recently launched on the market structural adhesive, making it essential to characterize it for the purpose of designing adhesive structures. For that, it is necessary to carry out bulk tensile tests to obtain mechanical properties such as Young's modulus (E), yield strength (y), tensile strength (f) and tensile failure strain (f). The Thick Adherend Shear Test (TAST) is also performed, which aims to characterize the shear mechanical properties, and allows to obtain the results of shear modulus (G), shear yield strength (𝜏y), shear strength (𝜏max) and shear failure strain (). Through the Double-Cantilever Beam (DCB) test, the critical strain energy release rate in mode I (GIC) is calculated using the Compliance Calibration Method (CCM), Corrected Beam Theory (CBT) and Compliance-Based Beam Method (CBBM). Finally, in the End-Notched Flexure (ENF) test, the critical strain energy release rate in mode II (GIIC) is calculated using the Compliance Calibration Method (CCM), Corrected Beam Theory (CBT) and Compliance-Based Beam methods Method (CBBM). After carrying out the aforementioned tests and analyzing the obtained data, it was found that there is good repeatability between test specimens from the same test and a convergence of the values of the adhesive characterized in the laboratory with the manufacturer's values.
In this new industrial era, and with the development of new materials, there has been a gradual increase in the replacement of components, which has come to warn of another situation that, in the global perspective of a design project, is not less important - joining the various components. In the remote and near past, joining was accomplished by mechanical components (rivets or screws) or by welding, but these methods have some drawbacks, such as increased weight, corrosive problems, loads concentrations in the joined areas and risk of cracking. Due to these drawbacks, the adhesive bonding solution for components appears. However, for the application of this technique and for the use of design tools that enable the designer to design adhesive structures, it is essential to know the most relevant mechanical and fracture properties of the adhesives to be used. This study presents the characterization of a recently launched on the market structural adhesive, making it essential to characterize it for the purpose of designing adhesive structures. For that, it is necessary to carry out bulk tensile tests to obtain mechanical properties such as Young's modulus (E), yield strength (y), tensile strength (f) and tensile failure strain (f). The Thick Adherend Shear Test (TAST) is also performed, which aims to characterize the shear mechanical properties, and allows to obtain the results of shear modulus (G), shear yield strength (𝜏y), shear strength (𝜏max) and shear failure strain (). Through the Double-Cantilever Beam (DCB) test, the critical strain energy release rate in mode I (GIC) is calculated using the Compliance Calibration Method (CCM), Corrected Beam Theory (CBT) and Compliance-Based Beam Method (CBBM). Finally, in the End-Notched Flexure (ENF) test, the critical strain energy release rate in mode II (GIIC) is calculated using the Compliance Calibration Method (CCM), Corrected Beam Theory (CBT) and Compliance-Based Beam methods Method (CBBM). After carrying out the aforementioned tests and analyzing the obtained data, it was found that there is good repeatability between test specimens from the same test and a convergence of the values of the adhesive characterized in the laboratory with the manufacturer's values.
Description
Keywords
Adesivo estrutural Junta adesiva Ductilidade Tenacidade à fratura Bulk Thick Adherend Shear Test Double-Cantilever Beam End-Notched Flexure Structural adhesive Adhesive joint Ductility Fracture toughness