| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| 7.54 MB | Adobe PDF |
Authors
Advisor(s)
Abstract(s)
Os adesivos estruturais são imensamente conhecidos e aceites pela comunidade científica e industrial como sendo materiais de engenharia de alto desempenho e o seu uso tem sido, cada vez mais, generalizado e adotado. Ainda assim, não se deve esquecer o facto de este método de união ser relativamente recente e estar em constante evolução. Porém, nenhuma outra técnica de união de materiais é tão polivalente, o que se deve essencialmente à sua contribuição para a integridade estrutural de componentes, à sua capacidade de unir materiais dissimilares e assim o adesivo se manter de forma permanente na montagem e, também, pela sua facilidade de fabrico e aplicação, redução de custos e tempos de produção. Embora a utilização de adesivos remonte à era préhistórica, nenhuma outra técnica de união admite e atende as necessidades atuais com tanto êxito. Estes têm sido os principais motivos pelos quais as ligações adesivas são adotadas pelo seio industrial, nomeadamente as indústrias automóveis, aeronáuticas e até mesmo as nucleares e aeroespaciais. Deste modo, e uma vez que os adesivos, tal como qualquer outro material, sofrem degradação devido a fatores externos como a temperatura, humidade e radiação, torna-se fundamental conhecer quais os efeitos que estes fenómenos, nomeadamente a radiação, provocam nas propriedades mecânicas e de fratura dos adesivos. Neste sentido, esta dissertação visa observar os efeitos que a radiação ionizante provoca nos adesivos, para diferentes períodos de exposição. Para isso, pretende-se fabricar provetes maciços de dois adesivos distintos, submetê-los a essas condições e determinar as suas principais propriedades mecânicas através da análise dos resultados alcançados na realização de ensaios de tração. A comparação desses dados com os obtidos para os provetes de referência não se verificou conclusiva. De facto, não existiram diferenças suficientes que pudessem aferir que a radiação influencia as propriedades mecânicas de adesivos estruturais, sendo a principal explicação o acontecimento simultâneo (e respetiva anulação) dos efeitos de reticulação e cisão da cadeia molecular dos adesivos.
Structural adhesives are immensely known and accepted by the scientific and industrial community as high-performance engineering materials and their use has been increasingly widespread and adopted. Even so, one should not forget the fact that this joining method is relatively recent and is in constant evolution. However, no other technique for bonding materials is as versatile, which is essentially due to its contribution to the structural integrity of components, its ability to bond dissimilar materials so that the adhesive remains permanently in the assembly and, also, for its ease of manufacture and application, reduction of costs and production times. Although the use of adhesives dates back to prehistoric times, no other joining technique accepts and meets current needs with such success. These have been the main reasons why adhesive bonds are adopted by industry, namely the automotive, aeronautical and even nuclear and aerospace industries. In this way, and since adhesives, like any other material, suffer degradation due to external factors such as temperature, humidity and radiation, it is essential to know what effects these phenomena, namely radiation, have on the mechanical properties. and breakage of adhesives. To this end, this dissertation aims to observe the effects that ionising radiation has on adhesives for different periods of exposure. The aim is to manufacture solid specimens of two different adhesives, subject them to these conditions and determine their main mechanical properties by analysing the results of tensile tests. Comparing these data with those obtained for the reference specimens was inconclusive. In fact, there were not enough differences to confirm that radiation influences the mechanical properties of structural adhesives, the main explanation being the simultaneous occurrence (and respective cancellation) of the effects of cross-linking and scission of the adhesive's molecular chain.
Structural adhesives are immensely known and accepted by the scientific and industrial community as high-performance engineering materials and their use has been increasingly widespread and adopted. Even so, one should not forget the fact that this joining method is relatively recent and is in constant evolution. However, no other technique for bonding materials is as versatile, which is essentially due to its contribution to the structural integrity of components, its ability to bond dissimilar materials so that the adhesive remains permanently in the assembly and, also, for its ease of manufacture and application, reduction of costs and production times. Although the use of adhesives dates back to prehistoric times, no other joining technique accepts and meets current needs with such success. These have been the main reasons why adhesive bonds are adopted by industry, namely the automotive, aeronautical and even nuclear and aerospace industries. In this way, and since adhesives, like any other material, suffer degradation due to external factors such as temperature, humidity and radiation, it is essential to know what effects these phenomena, namely radiation, have on the mechanical properties. and breakage of adhesives. To this end, this dissertation aims to observe the effects that ionising radiation has on adhesives for different periods of exposure. The aim is to manufacture solid specimens of two different adhesives, subject them to these conditions and determine their main mechanical properties by analysing the results of tensile tests. Comparing these data with those obtained for the reference specimens was inconclusive. In fact, there were not enough differences to confirm that radiation influences the mechanical properties of structural adhesives, the main explanation being the simultaneous occurrence (and respective cancellation) of the effects of cross-linking and scission of the adhesive's molecular chain.
Description
Keywords
Adesivos estruturais Ligações adesivas Propriedades mecânicas Degradação Radiação Structural adhesive Adhesive bond Mechanical properties Degradation Radiation