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Banea M.D.,Federal University of Rio de Janeiro | da Silva L.F.M.,University of Porto | Carbas R.J.C.,Institute Ciencia e Inovacao em Engineering Mecanica e Engineering Industrial INEGI | de Barros S.,Federal University of Rio de Janeiro
Journal of Adhesion | Year: 2016

In this work an innovative technique for multi-material adhesive joints debonding by combining the inductive heating method and the use of thermally expandable particles (TEPs) is presented. First, single lap joints (SLJs) using various combinations of adherends (high-strength steel (HS), aluminum (Al), and carbon fiber reinforced plastics (CFRP)) were fabricated and tested to assess the influence of TEP content on the lap-shear strength of the joints. Further, the ability of the TEP-modified joints to support temperature-controlled debonding was evaluated. It was showed that the control of debonding process by temperature is possible. The temperature needed for debonding is a function of TEP content and can be lowered by increasing the TEP content. Relatively similar debonding temperatures were found for multi-material/dissimilar joints debonding compared with similar joints, but more induction heating power is generally necessary to disassemble multi-material adhesive joints. © 2016 Taylor & Francis


Viana G.,Institute Ciencia e Inovacao em Engineering Mecanica e Engineering Industrial INEGI | Costa M.,Institute Ciencia e Inovacao em Engineering Mecanica e Engineering Industrial INEGI | Banea M.D.,Federal University of Rio de Janeiro | Da Silva L.F.M.,University of Porto
Journal of Adhesion | Year: 2016

Structural adhesives are increasingly being used in the aerospace and automotive industries. They allow for light weight vehicles, fuel savings, and reduced emissions. However, the environmental degradation of adhesive joints is a major setback in its wide implementation. Moisture degradation of adhesive joints includes plasticization, attacking of the interface, swelling of the adhesive and consequent creation of residual stresses. This may lead to reversible and irreversible damage. The main factors affecting the strength of adhesive joints under high and low temperatures are the degradation of the adhesive mechanical properties and the creation of residual stresses induced by different coefficients of thermal expansion (between the adhesive and the adherends). The effect of the combined effect of moisture and temperature is not yet fully understood. The aim of this study is to shed light on this subject. In this work bulk water absorption tests were conducted at different moisture conditions in order to assess the diffusion coefficient, maximum water uptake, and glass transition temperature. Aged and unaged small dogbone tensile specimens were tested under different temperature conditions. The glass transition temperature of the adhesives as a function of the water uptake was assessed. The aim is to determine the evolution of the properties of two epoxy adhesives as a function of two variables (environmental temperature and moisture). © 2016 Taylor & Francis


Silva M.R.G.,University of Porto | Marques E.A.S.,University of Porto | da Silva L.F.M.,Institute Ciencia e Inovacao em Engineering Mecanica e Engineering Industrial INEGI
Latin American Journal of Solids and Structures | Year: 2016

The automotive industry is increasingly using adhesive joints bonding advanced lightweight materials to reduce vehicle weight. Strength under impact loadings is a major concern for this application and mixed adhesive joints can effectively improve the joints by combining stiffness and flexibility on the same overlap. This work introduces and studies several configurations for static and impact tests of mixed adhesive joints with four adhesives in different combinations. The main purpose of this work is the development of a strong adhesive joint using a mixed adhesive layer and perform a series of mechanical to study its mechanical behaviour. It is concluded that the use of the mixed adhesive technique improves both static and impact strength by introducing flexibility to the joint which subsequently allows more energy absorption when introduced in crash resistant structures. © 2016, Latin American Journal of Solids and Structures. All rights reserved.


Marques E.A.S.,Institute Ciencia e Inovacao em Engineering Mecanica e Engineering Industrial INEGI | Campilho R.D.S.G.,Polytechnic Institute of Porto | Da Silva L.F.M.,University of Porto
Journal of Adhesion Science and Technology | Year: 2016

The use of adhesives for high-performance structural applications has significantly increased in the last decades. However, the use of adhesive joints in adverse environmental conditions is still limited due to the reduced capability of adhesives to withstand large thermal gradients. Dual adhesive joints, which contain two adhesives with remarkably different mechanical behaviours, are a technique suitable for being used in extreme temperatures. The object of this study is a ceramic-metal joint, representative of the thermal protection systems of some aerospace vehicles. In this paper, several joint-mixed joint geometries are presented, studied with recourse to finite element analysis. In a first phase, the three-dimensional finite element models and the material properties are validated against experimental data. In a second phase, the model geometry is modified, with the aim of understanding the effect of several changes in the joints mechanical behaviour and comparing the merits of each geometry. The models presented good agreement was found between experimental and numerical data and the alternative geometries allowed the introduction of additional flexibility on the joint but at the cost of lower failure load. © 2015 Taylor & Francis.

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