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Abstract(s)
As ligações adesivas são um método de ligação cada vez mais utilizado em diversas indústrias, muito por culpa das muitas vantagens que apresentam quando comparadas com outros métodos de ligação mais tradicionais. A distribuição mais uniforme de tensões, facilidade de fabricação, possibilidade de união de diferentes materiais, custo mais baixo e redução do peso são as vantagens que mais se destacam. Por estas razões, as juntas adesivas têm aumentado a sua aplicação em diversas indústrias, tais como automóvel, naval, aeroespacial, aeronáutica e calçado. Em relação aos adesivos, estes podem ser de vários tipos. O adesivo Araldite® AV138 é um exemplo de um adesivo rígido e frágil, enquanto o adesivo Araldite® 2015 é considerado um adesivo moderadamente dúctil, menos resistente, mas com maior flexibilidade. Para além destes adesivos, existem outros adesivos caracterizados por possuírem elevada resistência, flexibilidade e ductilidade, tais como o Sikaforce® 7752. A seleção do adesivo deve ser feita de forma cuidada, consoante as suas características e o tipo de solicitação a que vai estar sujeito. Esta dissertação tem como objetivo a realização de um estudo de juntas adesivas em T com aderentes de alumínio, ligados por três adesivos de características distintas e sujeitas a esforços de arrancamento, onde a espessura do aderente em L (tP2) varia. A análise numérica foi realizada com auxílio do software ABAQUS® e considerando o Método de Elementos Finitos eXtendido (MEFX). Outro objetivo desta dissertação é avaliar o MEFX como técnica de previsão de resistência de juntas adesivas, e verificar se se trata de uma ferramenta adequada e com um índice de fiabilidade aceitável. Foi realizada uma comparação entre resultados obtidos numericamente, através do MEFX, com resultados experimentais e numéricos obtidos num trabalho anterior. Na análise numérica foi realizada um estudo do modelo de dano baseado em tensões e deformações, a análise de tensões nas juntas, a análise da variável de dano e a previsão de resistência das juntas, onde é possível observar-se o efeito do critério de iniciação e da lei de propagação. Após a realização deste estudo, é possível concluir-se que o MEFX é um método adequado para a previsão de resistência de juntas adesivas em T, desde que usados critérios adequados de iniciação e propagação do dano.
Adhesive bonds are an increasingly used bonding method in various industries, much because of the many advantages they present compared to other more traditional bonding methods. The more uniform distribution of stresses, ease of manufacture, possibility of joining different materials, lower cost and reduction of weight are the advantages that stand out the most. For these reasons, adhesive joints have increased their application in several industries, such as automobile, naval, aerospace, aeronautics and footwear. Regarding adhesives, these may be of various types. The adhesive raldite® AV138 is an example of a stiff and brittle adhesive, while the adhesive Araldite® 2015 is considered a moderately ductile, less strong, but more flexible adhesive. In addition to these adhesives, there are other adhesives characterized by high strength, flexibility and ductility, such as Sikaforce® 7752. The selection of the adhesive ust be done carefully, depending on its characteristics and the type of application to which it will be subjected to. This dissertation aims to perform a study of adhesive Tjoints with aluminum adhesives, bonded by three adhesives with diferente characteristics and subjected to peeling stresses, where the L-adherend thickness (tP2) varies. The numerical analysis was performed with the aid of ABAQUS® software and considering the eXtended Finite Element Method (XFEM). Another objective of this dissertation is to evaluate the XFEM as a technique for predicting the strength of adhesive joints, and to verify if it is a suitable tool with an acceptable reliability index. A comparison was made between the numerical results, by XFEM, with experimental esults obtained in a previous work. In the numerical analysis, a study of the damage odel based on stresses and strains, joint stress analysis, damage variable analysis and joint strength prediction was performed, where it is possible to observe the effect of the initiation criterion and the propagation law. After this study, it is possible to conclude that the XFEM is a suitable method for the strength prediction of adhesive T-joints, provided that appropriate damage initiation and propagation criteria are used.
Adhesive bonds are an increasingly used bonding method in various industries, much because of the many advantages they present compared to other more traditional bonding methods. The more uniform distribution of stresses, ease of manufacture, possibility of joining different materials, lower cost and reduction of weight are the advantages that stand out the most. For these reasons, adhesive joints have increased their application in several industries, such as automobile, naval, aerospace, aeronautics and footwear. Regarding adhesives, these may be of various types. The adhesive raldite® AV138 is an example of a stiff and brittle adhesive, while the adhesive Araldite® 2015 is considered a moderately ductile, less strong, but more flexible adhesive. In addition to these adhesives, there are other adhesives characterized by high strength, flexibility and ductility, such as Sikaforce® 7752. The selection of the adhesive ust be done carefully, depending on its characteristics and the type of application to which it will be subjected to. This dissertation aims to perform a study of adhesive Tjoints with aluminum adhesives, bonded by three adhesives with diferente characteristics and subjected to peeling stresses, where the L-adherend thickness (tP2) varies. The numerical analysis was performed with the aid of ABAQUS® software and considering the eXtended Finite Element Method (XFEM). Another objective of this dissertation is to evaluate the XFEM as a technique for predicting the strength of adhesive joints, and to verify if it is a suitable tool with an acceptable reliability index. A comparison was made between the numerical results, by XFEM, with experimental esults obtained in a previous work. In the numerical analysis, a study of the damage odel based on stresses and strains, joint stress analysis, damage variable analysis and joint strength prediction was performed, where it is possible to observe the effect of the initiation criterion and the propagation law. After this study, it is possible to conclude that the XFEM is a suitable method for the strength prediction of adhesive T-joints, provided that appropriate damage initiation and propagation criteria are used.
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Keywords
Método de Elementos Finitos eXtendido Juntas adesivas Juntas em T Adesivo estrutural Ensaios experimentais eXtended Finite Element Method Adhesve joints T joints Structural adhesive Experimental tests