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Abstract(s)
Ao longo dos anos as ligações adesivas tornaram-se cada vez mais relevantes, quando se pretende utilizar um processo de ligação entre dois materiais distintos. Para além da sua utilização abrangente na maioria dos casos, o seu processo de fabrico apresenta geralmente um custo inferior aos restantes métodos de ligação. Para ser possível avaliar o desempenho e a resistência da junta adesiva, utilizam-se metodologias numéricas baseadas no Método de Elementos Finitos (MEF). Em casos reais, as ligações adesivas estão também sujeitas a cargas dinâmicas, como por exemplo de impacto. Devido à escassez de literatura sobre o comportamento das juntas adesivas ao impacto, o seu estudo tornou-se relevante para que todas as técnicas utilizadas e ensaios realizados sejam validados, para que seja possível prever o comportamento das juntas a este tipo de carregamentos. O principal objetivo desta dissertação é o estudo da influência dos parâmetros coesivos na previsão do comportamento e da resistência de juntas adesivas de sobreposição dupla (JSD) solicitadas ao impacto. Para o efeito, consideram-se simulações numéricas pelo MEF e modelos de dano coesivo (MDC). Inicialmente, foi realizada uma validação com dados experimentais, para validação da técnica proposta para análise de juntas adesivas ao impacto. Para avaliar a influência dos parâmetros coesivos, fez-se variar cada parâmetro coesivo desde -75% a 100% do parâmetro original em intervalos de 25%, mantendo os restantes inalterados. Os adesivos utilizados para este estudo numérico são o Araldite® AV138 e o Sikaforce® 7752. Como aderente utilizou-se em ambos os casos o pré-impregnado Seal® Texipreg HS 160 RM. A validação da técnica numérica proposta foi realizada com sucesso para a modelação de juntas adesivas ao impacto. Concluiu-se que os parâmetros coesivos estudados, exceto a tenacidade à tração (GIc), apresentam relevância no comportamento dos adesivos e, consequentemente, na previsão de resistência de juntas adesivas.
Over the years, adhesive bonds have become increasingly relevant when one intends to use a bonding process between two different materials. In addition to its widespread use in most cases, its manufacturing process is generally cheaper than for the other joining methods. To be able to evaluate the performance and strength of the adhesive joint, numerical methodologies based on the Finite Element Method (FEM) are used. In real cases, adhesive joints are also subjected to dynamic loads, such as impact. Due to the scarcity of literature on the behavior of adhesive joints under impact, its study has become relevant so that all the used techniques and tests performed are validated, so that it is possible to predict the behavior of the joints to this type of loading. The main objective of this dissertation is to study the influence of cohesive parameters in predicting the behavior and strength of double-lap joints under impact loads. For this purpose, numerical simulations by FEM and cohesive zone models (CZM) are considered. Initially, a study was carried out with experimental data, to validate the proposed technique for analyzing impact-adhesive joints. To evaluate the influence of the cohesive parameters, each cohesive parameter was varied from -75% to 100% of the original parameter at 25% intervals, keeping the rest unchanged. The adhesives used for this numerical study are the Araldite® AV138 and the Sikaforce® 7752. As adherend, the pre-preg Seal® Texipreg HS 160 RM was used in both cases. Validation of the proposed numerical technique was successfully accomplished to model bonded joints under impact loads. It was concluded that the cohesive parameters studied, except for a tensile toughness (GIc), present relevance in the behavior of adhesives and, consequently, in the strength prediction of adhesive joints.
Over the years, adhesive bonds have become increasingly relevant when one intends to use a bonding process between two different materials. In addition to its widespread use in most cases, its manufacturing process is generally cheaper than for the other joining methods. To be able to evaluate the performance and strength of the adhesive joint, numerical methodologies based on the Finite Element Method (FEM) are used. In real cases, adhesive joints are also subjected to dynamic loads, such as impact. Due to the scarcity of literature on the behavior of adhesive joints under impact, its study has become relevant so that all the used techniques and tests performed are validated, so that it is possible to predict the behavior of the joints to this type of loading. The main objective of this dissertation is to study the influence of cohesive parameters in predicting the behavior and strength of double-lap joints under impact loads. For this purpose, numerical simulations by FEM and cohesive zone models (CZM) are considered. Initially, a study was carried out with experimental data, to validate the proposed technique for analyzing impact-adhesive joints. To evaluate the influence of the cohesive parameters, each cohesive parameter was varied from -75% to 100% of the original parameter at 25% intervals, keeping the rest unchanged. The adhesives used for this numerical study are the Araldite® AV138 and the Sikaforce® 7752. As adherend, the pre-preg Seal® Texipreg HS 160 RM was used in both cases. Validation of the proposed numerical technique was successfully accomplished to model bonded joints under impact loads. It was concluded that the cohesive parameters studied, except for a tensile toughness (GIc), present relevance in the behavior of adhesives and, consequently, in the strength prediction of adhesive joints.
Description
Keywords
Método de Elementos Finitos Modelos de dano coesivo Impacto Ensaio de queda Junta de sobreposição dupla Adesivo estrutural Finite Element Method Cohesive Zone Models Impact Drop-test Double-lap Joints Structural adhesive