Estudo numérico-experimental da resistência e rigidez ao rolling shear de elementos de MLCC (Madeira Lamelada Colada Cruzada)
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Data
2023-02-24
Autores
Silva, João Vítor Felippe
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Este trabalho teve como objetivo o estudo numérico e experimental da rigidez (Gvt) e da resistência (fvt), associadas ao efeito de rolling shear, em elementos de Madeira Lamelada Colada Cruzada (MLCC), fabricados com três camadas de madeiras de florestas plantadas do Brasil e colados com adesivo poliuretano bi-componente. Foram utilizadas quatro diferentes espécies de madeira (Pinus elliottii, Eucalyptus grandis, Toona ciliata e Acrocarpus fraxinifolius) na fabricação dos painéis de MLCC. Incialmente foi realizado um levantamento bibliográfico sobre o tema com base na literatura nacional e internacional disponíveis. Paralelamente foi realizada a caracterização físico-mecânicas das madeiras e a análise da pressão de fabricação na resposta da qualidade de colagem da MLCC, considerando-se cinco níveis de pressão que variaram de 0,1 MPa a 1,3 MPa. Os valores de rigidez e resistência ao rolling shear foram determinadas experimentalmente por três métodos de ensaio: flexão de vigas, cisalhamento vertical em corpo de prova e cisalhamento inclinado, também em corpos de prova. Foi realizado também um estudo numérico com base no método dos elementos finitos (MEF) com uso do software ANSYS e um estudo analítico complementar para avaliação dos métodos de cálculo disponíveis na literatura: “gama”, “k” e de “Kreuzinger”. Como resultado, observou-se que a pressão de fabricação não teve efeito significativo na porcentagem de delaminação e nem na espessura da linha de cola da MLCC, ao contrário da resistência ao cisalhamento na linha de cola que teve desempenho superior para a pressão de 0,7 MPa. Os valores de Gvt obtidos pelos métodos de flexão em vigas e de cisalhamento inclinado em corpo de prova ficaram próximos entre si e ambos e foram maiores que os valores obtidos pelo método de cisalhamento vertical. Os três modelos de ensaio analisados apresentaram resultados semelhantes para fvt. Os modos de falha obtidos experimentalmente foram compativeis com as distribuições das tensões observadas nos modelos numéricos nas regiões mais solicitadas. As respostas dos métodos analíticos foram significativamente diferentes entre si, sendo o método gama o mais sensível aos valores das propriedades de resistência e de elasticidade da MLCC, como também o que apresentou os resultados mais proximos dos resultados experimentais. Como principais contribuições deste trabalho recomenda-se, para madeiras de reflorestamento brasileiras com ρ12% entre 380 kg/m3 e 480 kg/m3: o modelo de corpo de prova de cisalhamento inclinado para determinação da rigidez e resistência ao rolling shear em elementos de MLCC; a pressão de fabricação de pelo menos 0,7 MPa; o método analítico “gama”, e limite de delaminação total de 10%.
The aim of this work was the numerical and experimental study of rolling shear stiffness (Gvt) and strength (fvt) of three layers Cross Laminated Timber (CLT) manufactured of wood from forests planted in Brazil and two-component polyurethane adhesive. Four wood species were used (Pinus elliottii, Eucalyptus grandis, Toona ciliata and Acrocarpus fraxinifolius), for CLT manufacturing. Initially, a bibliographic survey was carried out on the subject based on national and international available literature. Along with that the physical-mechanical characterization of the woods pieces and the evaluation of the manufacturing pressure were carried out for five pressure levels ranging from 0.1 MPa to 1.3 MPa. Rolling shear stiffness and strength were determined by three test methods: beam bending, vertical shear test piece and inclined shears. A numerical study was also carried out based on the finite element method (FEM) using ANSYS software; it was also developed a complementary analytical study using the “gamma”, “k” and “Kreuzinger” design methods available on the literature. The manufacturing pressure had no significant effect on the delamination percentage and thickness glue line of the CLT; however the strength in the glue line had a superior performance at the pressure of 0.7 MPa. The Gvt values obtained by the beam bending and inclined shear specimens methods were higher than those obtained by the vertical shear method. The three analyzed test models results of fvt were similar. The experimental failure modes were compatible with the stress distributions in the numerical models. The responses of the analytical methods differed significantly from each other, as the gamma method was the most sensitive to the stiffness and strength properties of CLT, which results were closer to the experimental ones. As main contributions of this work, it is recommended, for Brazilian reforestation woods with ρ12% between 380 kg/m3 and 480 kg/m3: the inclined shear specimen model for determination of stiffness and strength to rolling shear for CLT elements; the manufacturing pressure of at least 0.7 MPa; the “gamma” analytical method, and a total delamination limit of 10%.
The aim of this work was the numerical and experimental study of rolling shear stiffness (Gvt) and strength (fvt) of three layers Cross Laminated Timber (CLT) manufactured of wood from forests planted in Brazil and two-component polyurethane adhesive. Four wood species were used (Pinus elliottii, Eucalyptus grandis, Toona ciliata and Acrocarpus fraxinifolius), for CLT manufacturing. Initially, a bibliographic survey was carried out on the subject based on national and international available literature. Along with that the physical-mechanical characterization of the woods pieces and the evaluation of the manufacturing pressure were carried out for five pressure levels ranging from 0.1 MPa to 1.3 MPa. Rolling shear stiffness and strength were determined by three test methods: beam bending, vertical shear test piece and inclined shears. A numerical study was also carried out based on the finite element method (FEM) using ANSYS software; it was also developed a complementary analytical study using the “gamma”, “k” and “Kreuzinger” design methods available on the literature. The manufacturing pressure had no significant effect on the delamination percentage and thickness glue line of the CLT; however the strength in the glue line had a superior performance at the pressure of 0.7 MPa. The Gvt values obtained by the beam bending and inclined shear specimens methods were higher than those obtained by the vertical shear method. The three analyzed test models results of fvt were similar. The experimental failure modes were compatible with the stress distributions in the numerical models. The responses of the analytical methods differed significantly from each other, as the gamma method was the most sensitive to the stiffness and strength properties of CLT, which results were closer to the experimental ones. As main contributions of this work, it is recommended, for Brazilian reforestation woods with ρ12% between 380 kg/m3 and 480 kg/m3: the inclined shear specimen model for determination of stiffness and strength to rolling shear for CLT elements; the manufacturing pressure of at least 0.7 MPa; the “gamma” analytical method, and a total delamination limit of 10%.
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Palavras-chave
Cross Laminated Timber, Rolling Shear, Resistência e rigidez, Qualidade de colagem, Simulação numérica, Adesivo poliuretano, Stiffness and Strength, Bonding Quality, Numerical simulation, Castor oil adhesive, Painéis de madeira, Estruturas de madeira (Construção civil), Trabalhos em madeira