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Abstract(s)
Para aumentar a confiança no design de estruturas adesivas, é importante prever com precisão a sua resistência mecânica. Neste contexto, as abordagens da mecânica da fratura possuem vantagens significativas em relação à mecânica dos meios contínuos. A abordagem da mecânica da fratura é frequentemente aplicada por uma análise energética, onde o parâmetro principal para prever a evolução do dano e da fenda é a taxa crítica de libertação de energia de deformação (GC). Este parâmetro também pode ser dividido em componentes de tração (GIC) e corte (GIIC). Os modelos de dano coesivo (MDC) são uma técnica poderosa de previsão de resistência no âmbito da mecânica de fratura e usam leis coesivas para induzir crescimento da fenda nos modelos numéricos. Este trabalho tem como objetivo estimar GIIC de juntas adesivas de estruturas compósitas pelo ensaio End-Notched Flexure (ENF), considerando diferentes valores de espessura de adesivo (ta). Neste contexto, são comparados diferentes métodos de redução de dados para estimar GIIC. Por outro lado, as leis coesivas de corte da camada adesiva são obtidas pelo método de elementos finitos (MEF) e MDC usando uma técnica inversa, que permita compreender a influência de ta no comportamento de corte das ligações. Os modelos numéricos capturaram com precisão o comportamento experimental observado do adesivo. Foi encontrada uma clara dependência em relação a GIIC e a resistência coesiva ao corte (ts 0), dependendo de ta.
To increase the confidence in the design of bonded structures, it is important to accurately predict their mechanical strength. In this context, Fracture and Damage Mechanics approaches have significant advantages over Continuum Mechanics. The Fracture Mechanics approach is often applied by an energetic analysis, where the main parameter to predict the evolution of damage and failure is the critical strain energy release rate (GC). This parameter can also be divided into the tensile (GIC) and shear (GIIC) components. Cohesive Zone Models (CZM) are a powerful strength prediction technique within the scope of Fracture Mechanics and take advantage of cohesive laws to induce crack growth in the numerical models. This work aims to estimate GIIC of adhesive joints of composite structures by the End-Notched Flexure (ENF) test, considering different values of adhesive thickness (ta). In this context, different data reduction methods to estimate GIIC are compared. On the other hand, the shear cohesive laws of the adhesive layer are obtained by the Finite Element Method (FEM) and CZM using an inverse technique, enabling to understand the influence of ta on the joints’ shear behaviour. The numerical models accurately captured the observed experimental behaviour of the adhesive. A clear dependency was found regarding both GIIC and the shear cohesive strength (ts 0), depending on ta.
To increase the confidence in the design of bonded structures, it is important to accurately predict their mechanical strength. In this context, Fracture and Damage Mechanics approaches have significant advantages over Continuum Mechanics. The Fracture Mechanics approach is often applied by an energetic analysis, where the main parameter to predict the evolution of damage and failure is the critical strain energy release rate (GC). This parameter can also be divided into the tensile (GIC) and shear (GIIC) components. Cohesive Zone Models (CZM) are a powerful strength prediction technique within the scope of Fracture Mechanics and take advantage of cohesive laws to induce crack growth in the numerical models. This work aims to estimate GIIC of adhesive joints of composite structures by the End-Notched Flexure (ENF) test, considering different values of adhesive thickness (ta). In this context, different data reduction methods to estimate GIIC are compared. On the other hand, the shear cohesive laws of the adhesive layer are obtained by the Finite Element Method (FEM) and CZM using an inverse technique, enabling to understand the influence of ta on the joints’ shear behaviour. The numerical models accurately captured the observed experimental behaviour of the adhesive. A clear dependency was found regarding both GIIC and the shear cohesive strength (ts 0), depending on ta.
Description
Keywords
Juntas adesivas Adesivos estruturais End-Notched Flexure (ENF) Espessura adesiva Modelos de Dano Coesivo Taxa crítica de libertação de energia Método de Elementos Finitos Adhesive joint Structural adhesive Adhesive thickness Cohesive Zone Models Critical rate of energy release Finite Element Method