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Authors
Abstract(s)
O uso de juntas adesivas em aplicações automóveis tem vindo a aumentar uma vez que
oferecem potencial para redução tanto do peso como do custo de fabricação. Contudo, com a
tendência actual para construção de veículos mais leves e com reduzidas emissões de CO2, os
construtores automóveis estão a aumentar o uso de materiais de baixa densidade, tais como, polímeros
reforçados com fibra de carbono (CFRP) ou super ligas, materiais dispendiosos, que levam à
necessidade de reaproveitamento dos mesmos. Assim, por razões ambientais e económicas, o
desenvolvimento de novas tecnologias e procedimentos capazes de desunir facilmente as juntas
adesivas (sem danificar os componentes a ligar) assume um grande interesse por parte da indústria
automóvel.
Seguindo esta tendência, a possibilidade de desunir quando necessário ligações adesivas foi
investigada ao longo desta tese, usando juntas simples unidas com adesivos modificados com
partículas termo expansíveis (TEPs’). Foram usados dois adesivos diferentes para comparar o efeito
dos TEPs’ em cada um. Foram também efectuados ensaios de tracção para perceber qual a
percentagem ideal de TEPs’ de forma a permitir, se necessário, uma fácil desunião de junta sem
comprometer os requerimentos de força de adesão. Os resultados são comparados com juntas simples
dos mesmos adesivos sem qualquer adição de TEPs. Desta comparação concluiu-se que com o
aumento de % de TEPs no adesivo a força de resistência de sobreposição diminui.
Para descobrir o melhor/mais rápido procedimento para desunir as juntas foi aplicado calor
localmente durante alguns segundos, determinou-se a eficiência de desunião de juntas através da
expansão dos TEPs’ para cada percentagem de TEPs’ utilizada.
Como era esperado com o aumento da percentagem de TEPs’ no adesivo faz com que a
ligação adesiva quebre a temperaturas mais baixas.
ABSTRACT: Adhesive joints have been increasingly used in automotive applications because they offer a potential for reduced weight and cost [1]. However, with the current tendency to manufacture more low-weight and low-emission vehicles, the manufacturers are increasingly using low-density materials such as carbon fiber reinforced polymers (CFRP) or super alloys, usually expensive materials, which lead to a higher demand for recyclability. Thus, for environmental and economic reasons, the development of new technologies and processes that enable easy disassembly of the adhesive joints (without damaging the components) is becoming of great interest for the industry. To follow this tendency, the possibility of debonding on command of adhesive joints was investigated during this research, using single lap joints (SLJs) bonded with adhesives modified with thermally expandable particles (TEPs’). Two different adhesives were used to compare the TEPs’ effect on both adhesives and strength tests were performed to find the ideal TEPs’ percentage to achieve an easy disassembly, if needed, of the bonded joints, while guarantying the joint strength requirements. All the results were compared with single lap joints (SLJs) of those adhesives without any TEPs’. An evaluation was performed with this comparison and it was concluded that with the increase of %wt of TEPs’ the lap shear strength decreases. To determine the best/faster way to disassemble the joints, they were locally heated for a few seconds and the joint disassembly effectiveness due to TEPs' activation was evaluated and compared between different %wt of TEPs’. As was expected, with the increase of %wt of TEPs’ the temperature needed to dissemble the joints decreases.
ABSTRACT: Adhesive joints have been increasingly used in automotive applications because they offer a potential for reduced weight and cost [1]. However, with the current tendency to manufacture more low-weight and low-emission vehicles, the manufacturers are increasingly using low-density materials such as carbon fiber reinforced polymers (CFRP) or super alloys, usually expensive materials, which lead to a higher demand for recyclability. Thus, for environmental and economic reasons, the development of new technologies and processes that enable easy disassembly of the adhesive joints (without damaging the components) is becoming of great interest for the industry. To follow this tendency, the possibility of debonding on command of adhesive joints was investigated during this research, using single lap joints (SLJs) bonded with adhesives modified with thermally expandable particles (TEPs’). Two different adhesives were used to compare the TEPs’ effect on both adhesives and strength tests were performed to find the ideal TEPs’ percentage to achieve an easy disassembly, if needed, of the bonded joints, while guarantying the joint strength requirements. All the results were compared with single lap joints (SLJs) of those adhesives without any TEPs’. An evaluation was performed with this comparison and it was concluded that with the increase of %wt of TEPs’ the lap shear strength decreases. To determine the best/faster way to disassemble the joints, they were locally heated for a few seconds and the joint disassembly effectiveness due to TEPs' activation was evaluated and compared between different %wt of TEPs’. As was expected, with the increase of %wt of TEPs’ the temperature needed to dissemble the joints decreases.
Description
Mestrado em parceria com a Faculdade de Engenharia do Porto
Keywords
Adesivos Partículas Termo Expansíveis Nanopartículas Reciclagem Indústria Automóvel Juntas de Sobreposição Simples Desunião de Juntas