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Projeto de investigação
Design of 2D and 3D Polymer Based Composite Metamaterials with Tailored Thermomechanical Properties
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Structural metamaterials with negative mechanical/thermomechanical indices
Publication . Cardoso, João O.; Borges, João Paulo; Velhinho, Alexandre; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); Elsevier
Structural metamaterials presenting negative values of one or more mechanical and thermomechanical indices – namely the Poisson's ratio, the linear compressibility, and the coefficient of thermal expansion – are the promising candidates to the applications in many fields, ranging from precision mechanics to biomedical devices or energy absorption. Although scattered mentions may be found in the literature since the late eighties of 20th century, the systematic research efforts concerning these materials became effective much later. The present work is to review the main scientific contributions to the topic in the last five years. This paper first deals with those metamaterials showing a single negative index, and then proceeds to analyze the much less frequent instances of coupled negative indices, with emphasis on the so-called anepectic case, which exhibits an unusual thermomechanical response.
Methodology for modelling and simulation of tailored 3D functionally graded auxetic metamaterials
Publication . Páscoa, Frederico T.; Machado, Carla M.; Cardoso, João O.; Borges, João Paulo; Velhinho, Alexandre; DEMI - Departamento de Engenharia Mecânica e Industrial; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); Springer Science Business Media
The description of methodologies for modelling auxetic structures with functional gradient and simulating their behaviour under loading is lacking in the literature, despite an increase of the interest in auxetics and the quantity of experimental data on these structures. This work proposes a method that allows modelling of tailored complex functionally graded auxetic structures, achieved through modifications in the equations defining the basic surfaces that characterize the aforementioned structures. In this method, the simulation studies were performed by means of the finite element method. To showcase the capabilities of this method with complex geometries, the gyroid surface was the chosen example from which to form the auxetic structures. The study was performed on geometries with different gradient types and steepness’s to obtain comprehensive data that allows to infer on the accuracy of the method. The obtained results demonstrate that even for large deformations (> 10%), the simulations concur with the experimental results. The good agreement between computational and experimental results points out the validation of the proposed methodology and the further application for various auxetic structures.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
OE
Número da atribuição
SFRH/BD/146227/2019