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Advisor(s)
Abstract(s)
As estruturas sandwich apresentam uma muito interessante combinação de boas propriedades mecânicas e baixo peso. Esta combinação leva a que estas sejam cada vez mais procuradas em vários setores industriais, com diversas aplicações. Muitas delas possuem elevado grau de exigência, pelo que é crucial conhecer, a priori, com elevado grau de fiabilidade, o comportamento destas estruturas em serviço. Neste trabalho, analisam-se experimental e numericamente quatro configurações de estrutura sandwich, com diferentes núcleos (espumas de polimetacrilimida (PMI) e politetileno tereftalato (PET)) e empilhamento das peles (laminados em material compósito). São realizados ensaios de flexão em três e quatro pontos para avaliar o comportamento das estruturas, através de curvas força-deslocamento e outros parâmetros, como a carga máxima de ensaio. Relativamente à análise numérica, utilizase o método dos elementos finitos para simular os ensaios de flexão, sendo empregues critérios de falha específicos para os diferentes constituintes da estrutura. Esta potencialidade do método é muito importante na análise de estruturas sandwich, uma vez que peles, núcleo e adesivo possuem comportamentos bastante distintos e, assim, é possível simular e validar a rotura dos constituintes. Globalmente, a análise numérica revela boa concordância com os ensaios experimentais e foi possível prever o comportamento linear e não-linear das estruturas sandwich com boa precisão. Além disso, a técnica utilizada prevê adequadamente os modos de rotura e a capacidade de carga (com pequenas variações) dos provetes testados, pelo que pode ser utilizada, com confiança, no projeto destas estruturas.
Sandwich structures present a very interesting combination of good mechanical properties and low weight. This combination leads to a growing demand of such structures, in multiple industry sectors, with distinct applications. Many of these possess a high degree of responsibility, which is why it is crucial to assess, in firsthand, with elevated reliability, the behavior of these structures in service. In this work, four configurations of sandwich structure, with different cores (PMI and PET foams) and ply stacking sequence, are experimental and numerically analyzed. Three and four point bending tests are performed in order to assess the behavior of the structures, through load-displacement curves and other parameters, such as the maximum load during testing. Regarding the numerical analysis, the finite element method is used to simulate the bending tests, and specific failure criterium are employed for the different constituents of the structure. Such capability is very important in sandwich structures’ analysis because skins, core and adhesive have quite different behaviors and, this way, it is possible to simulate and validate the failure of the constituents. Overall, the numerical analysis shows good agreement with the experimental tests, and it was able to predict the linear and non-linear behavior of the sandwich structures with good precision. Besides, the used technique accurately predicts the failure modes and the maximum load (with small variations) of the tested specimens, and, therefore, can be used, with confidence, in the project of these structures.
Sandwich structures present a very interesting combination of good mechanical properties and low weight. This combination leads to a growing demand of such structures, in multiple industry sectors, with distinct applications. Many of these possess a high degree of responsibility, which is why it is crucial to assess, in firsthand, with elevated reliability, the behavior of these structures in service. In this work, four configurations of sandwich structure, with different cores (PMI and PET foams) and ply stacking sequence, are experimental and numerically analyzed. Three and four point bending tests are performed in order to assess the behavior of the structures, through load-displacement curves and other parameters, such as the maximum load during testing. Regarding the numerical analysis, the finite element method is used to simulate the bending tests, and specific failure criterium are employed for the different constituents of the structure. Such capability is very important in sandwich structures’ analysis because skins, core and adhesive have quite different behaviors and, this way, it is possible to simulate and validate the failure of the constituents. Overall, the numerical analysis shows good agreement with the experimental tests, and it was able to predict the linear and non-linear behavior of the sandwich structures with good precision. Besides, the used technique accurately predicts the failure modes and the maximum load (with small variations) of the tested specimens, and, therefore, can be used, with confidence, in the project of these structures.
Description
Keywords
Estruturas sandwich Modelação numérica Método de elementos finitos Modelo crushable foam Critérios de falha Sandwich structures Numerical modelling Finite element method Crushable foam model Failure criteria