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Projeto de investigação
Metal-to-composite joining for space applications
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Influence of multiple debonding defects on the behaviour of mechanically anchored CFRP-to-steel joints
Publication . Biscaia, Hugo C.; D'Antino, Tommaso; Coelho, Pedro; Conde, Fábio; DEMI - Departamento de Engenharia Mecânica e Industrial; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; Elsevier
Carbon fibre-reinforced polymer (CFRP) externally bonded reinforcement (EBR) is commonly used to improve the strength of degraded steel structures. However, the CFRP composite is prone to debond from the substrate prematurely. To prevent its debonding, the use of mechanical anchorages is a primary option. Since controlling the adherence beneath the mechanical anchorage is difficult, it is important to better understand the bond performance of CFRP-to-steel interfaces in the presence of multiple debonding defects. To study this topic, a new numerical approach based on the finite difference method (FDM) is proposed and developed. Its validation is achieved by comparing results with a commercial finite element software package. Two different debonding defects are considered, localized and randomly dispersed, and four different ratios between the debonded and bonded areas are considered. Moreover, brittle and ductile adhesives are assumed, which result in triangular and trapezoidal bond-slip relationships, respectively. The results mainly showed that the combination of brittle adhesives and localized debonding defects leads to lower maximum load degradations than those found with dispersed debonding defects. Also, the friction angle is identified as the parameter with the highest influence on the bond performance of the mechanically anchored CFRP-to-steel joints.
Theoretical study on the bond performance of CFRP-to-steel single-lap shear tests with multiple debonding defects
Publication . Biscaia, Hugo C.; Coelho, Pedro; Conde, Fábio; D'Antino, Tommaso; DEMI - Departamento de Engenharia Mecânica e Industrial; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; Faculdade de Ciências e Tecnologia (FCT); Elsevier
The amount of research on the external bonding of Carbon Fiber Reinforced Polymers (CFRP) to degraded structures has increased recently. The adhesive is the weakest element of the joint and the bonding of the adherends is critical for the efficiency of the joint. Therefore, the influence of multiple debonding defects on CFRP-to-steel joints has still not been correctly quantified nor fully understood. For this reason, the current work proposes a new numerical strategy that allows for studying the influence of multiple debonding defects when a brittle and ductile adhesive is used. A new nonlinear bond-slip relationship is used and four different ratios between the debonded and the bonded area (η) are assumed: 0%, 25%, 50%, and 75%. The proposed model is based on the Finite Difference Method (FDM) and validation is carried out with a commercial Finite Element Method (FEM) package. The load-slip curves allowed for observing that the proposed FDM and the FEM are consistent and both revealed degradation of the load capacity of the joints with the increase of η. Moreover, by adopting a displacement control at the CFRP-free end, a snap-through and snap-back phenomenon are observed in the specimens with a localized debonding defect.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
Concurso de Projetos de Investigação de Caráter Exploratório (PeX) em Todos os Domínios Científicos
Número da atribuição
EXPL/EME-APL/0994/2021