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Abstract(s)
Os adesivos estruturais são materiais de base polimérica cujo comportamento mecânico é bastante
afetado pelas condições ambientais de temperatura e humidade. Em algumas aplicações,
nomeadamente na indústria aeronáutica, os adesivos podem estar sujeitos a ciclos de temperatura
que variam entre situações de temperaturas negativas e temperaturas positivas, facto que é
designado por ciclos de gelo/degelo.
Tendo por referência a temática das juntas adesivas e o estudo dos fatores que afetam a sua
durabilidade, esta dissertação faz um levantamento do estado da arte das ligações adesivas com
propósitos estruturais, nomeadamente, vantagens e desvantagens que a sua utilização em
diferentes áreas industriais comporta, tipologias mais usadas, distribuição de tensões quando
sujeitas a carregamentos tipificados, bem como os métodos de tratamento das superfícies para
garantir uma boa adesão entre o adesivo e o substrato.
Considerando o enfoque na envolvente ambiental, é abordado de forma mais extensiva o efeito
dessas condições sobre a durabilidade, fazendo referência a estudos relevantes que avaliaram o
efeito da submissão a uma exposição cíclica de variações térmicas tipo gelo/degelo. Os principais
ensaios normalizados para a avaliação da durabilidade são igualmente referidos como forma de
introduzir exploratoriamente a metodologia experimental assente na realização de ensaios
mecânicos para medição da evolução da resistência máxima, módulo de elasticidade e capacidade
de deformação com o tempo de exposição às condições ambientais definidas.
Structural adhesives are polymer-based materials whose mechanical behaviour is greatly affected by environmental conditions of temperature and humidity. In some applications, namely in the aeronautical industry, adhesives may be subject to temperature cycles that vary between negative and positive temperatures, a fact that is called freeze/thaw cycles. Having as a reference the topic of adhesive joints and the study of the factors that affect their durability, this dissertation surveys the state of the art of adhesive joints for structural purposes, namely, the advantages and disadvantages of their use in different industrial areas, the most commonly used typologies, stress distribution when subjected to typified loads, as well as the methods of surface treatment to ensure good adhesion between the adhesive and the substrate. Considering the focus on the environment, the effect of these conditions on durability is more extensively addressed, making reference to relevant studies that have evaluated the effect of submission to a cyclic exposure to frost/thaw type thermal variations. The main standardised tests for durability assessment are also referred to as a way of exploratorily introducing the experimental methodology based on mechanical tests for measuring the evolution of ultimate strength, modulus of elasticity and deformation capacity with exposure time to the defined environmental conditions.
Structural adhesives are polymer-based materials whose mechanical behaviour is greatly affected by environmental conditions of temperature and humidity. In some applications, namely in the aeronautical industry, adhesives may be subject to temperature cycles that vary between negative and positive temperatures, a fact that is called freeze/thaw cycles. Having as a reference the topic of adhesive joints and the study of the factors that affect their durability, this dissertation surveys the state of the art of adhesive joints for structural purposes, namely, the advantages and disadvantages of their use in different industrial areas, the most commonly used typologies, stress distribution when subjected to typified loads, as well as the methods of surface treatment to ensure good adhesion between the adhesive and the substrate. Considering the focus on the environment, the effect of these conditions on durability is more extensively addressed, making reference to relevant studies that have evaluated the effect of submission to a cyclic exposure to frost/thaw type thermal variations. The main standardised tests for durability assessment are also referred to as a way of exploratorily introducing the experimental methodology based on mechanical tests for measuring the evolution of ultimate strength, modulus of elasticity and deformation capacity with exposure time to the defined environmental conditions.
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Keywords
Adhesives durability tests simple overlay freeze/thaw