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Caracterização experimental e numérica de juntas adesivas com aderentes compósitos fabricados por impressão 3D
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Abstract(s)
Observa-se uma necessidade crescente de explorar soluções de união estrutural em materiais produzidos por fabrico aditivo uma vez que, apesar da flexibilidade e vantagens da impressão 3D, subsistem limitações no fabrico de peças de grandes dimensões e na resistência intrínseca dos materiais compósitos impressos. As juntas adesivas assumem-se, assim, como uma alternativa eficiente aos métodos tradicionais, pois permitem a união de diferentes componentes sem comprometer as propriedades mecânicas, reduzem concentrações de tensões e ampliam as possibilidades de aplicação destes materiais em contextos industriais. A presente dissertação pretendeu caracterizar experimentalmente e numericamente juntas adesivas com aderentes com e sem reforço de fibras de carbono fabricados por impressão 3D. Inicialmente, foi conduzido um trabalho experimental que incluiu a produção de provetes em poliamida com e sem reforço de fibra de carbono. Estes provetes foram submetidos a ensaios de tração para determinação das propriedades mecânicas e, posteriormente, utilizados na
fabricação de três tipologias distintas de juntas adesivas: juntas de sobreposição simples, juntas em degrau e juntas de chanfro interior. Através destes ensaios foi possível recolher informação relativa à rigidez, resistência máxima, modos de rotura e energia de fratura, bem como observar o comportamento diferenciado de cada configuração geométrica. Em paralelo, foi desenvolvido um modelo numérico com recurso ao Método dos Elementos Finitos, implementado em Abaqus®, que aplicou um modelo de dano coesivo baseado numa lei triangular para modelar o comportamento do adesivo. Os resultados numéricos foram comparados com os resultados experimentais. Como resultado do trabalho realizado foi validada a técnica numérica para a previsão da resistência das juntas adesivas e recomendada a geometria de junta para maximizar a resistência. Assim, tanto os ensaios experimentais como as simulações numéricas comprovaram a aplicabilidade das juntas adesivas em materiais fabricados por impressão 3D. A junta de chanfro interior destacou-se como a mais promissora, conjugando maior resistência, melhor distribuição de tensões e maior capacidade de dissipação de energia, pelo que representa a solução mais eficaz para aplicações estruturais que exijam desempenho mecânico elevado e fiabilidade.
There is a growing need to explore structural bonding solutions in materials produced by additive manufacturing because, despite the flexibility and advantages of 3D printing, there are still limitations in the manufacture of large parts and in the intrinsic strength of printed composite materials. Adhesive joints are therefore an efficient alternative to traditional methods, as they allow different components to be joined without compromising mechanical properties, reduce stress concentrations, and expand the possibilities for applying these materials in industrial contexts. This dissertation aimed to experimentally and numerically characterize adhesive joints having adherends with and without carbon fiber reinforcement manufactured by 3D printing. Initially, experimental work was conducted that included the production of polyamide test specimens with and without carbon fiber reinforcement. These specimens were subjected to tensile tests to determine their mechanical properties and were subsequently used in the manufacture of three different types of adhesive joints: single-lap joints, step joints, and scarf joints. Through these tests, it was possible to collect information on stiffness, maximum strength, failure modes, and fracture energy, as well as to observe the different behavior of each geometric configuration. In parallel, a numerical model was developed using the Finite Element Method, implemented in Abaqus®, which applied a cohesive zone model based on a triangular law to model the behavior of the adhesive. The numerical results were compared with the experimental results. As a result of the work carried out, the numerical technique to predicte the strength of adhesive joints was validated and the joint geometry to maximize strength recommended. Both experimental tests and numerical simulations have proven the applicability of adhesive joints in materials manufactured by 3D printing. The scarf joint stood out as the most promising, combining greater strength, better stress distribution and greater energy dissipation capacity, making it the most effective solution for structural applications that require high mechanical performance and reliability.
There is a growing need to explore structural bonding solutions in materials produced by additive manufacturing because, despite the flexibility and advantages of 3D printing, there are still limitations in the manufacture of large parts and in the intrinsic strength of printed composite materials. Adhesive joints are therefore an efficient alternative to traditional methods, as they allow different components to be joined without compromising mechanical properties, reduce stress concentrations, and expand the possibilities for applying these materials in industrial contexts. This dissertation aimed to experimentally and numerically characterize adhesive joints having adherends with and without carbon fiber reinforcement manufactured by 3D printing. Initially, experimental work was conducted that included the production of polyamide test specimens with and without carbon fiber reinforcement. These specimens were subjected to tensile tests to determine their mechanical properties and were subsequently used in the manufacture of three different types of adhesive joints: single-lap joints, step joints, and scarf joints. Through these tests, it was possible to collect information on stiffness, maximum strength, failure modes, and fracture energy, as well as to observe the different behavior of each geometric configuration. In parallel, a numerical model was developed using the Finite Element Method, implemented in Abaqus®, which applied a cohesive zone model based on a triangular law to model the behavior of the adhesive. The numerical results were compared with the experimental results. As a result of the work carried out, the numerical technique to predicte the strength of adhesive joints was validated and the joint geometry to maximize strength recommended. Both experimental tests and numerical simulations have proven the applicability of adhesive joints in materials manufactured by 3D printing. The scarf joint stood out as the most promising, combining greater strength, better stress distribution and greater energy dissipation capacity, making it the most effective solution for structural applications that require high mechanical performance and reliability.
Description
Keywords
3D printing Adhesive joints Finite Element Method (FEM) Cohesive zone model structural strength Failure mode and fracture energy Impressão 3D Juntas adesivas Método dos Elementos Finitos (MEF) Modelo de dano coesivo Resistência estrutural Modo e energia de rotura