Roberto Fujiyama

On the Strengthening of Cement Mortar by Natural Fibers

The purpose of this work is to evaluate mechanical behavior of sisal fiber reinforced cement mortar. The composite material was produced from a mixture of sand, cement and water. Sisal fibers were added to the mixture in two different lengths. Mechanical characterization of the composite and the plain mortar was carried out using three point bend, compression and impact tests. Specimens containing parallel sided notches of different root radii were loaded in three point bending in order to determine the effect of the fibers on the material fracture toughness in the presence of discontinuities. According to the results, while fiber reinforcement leads to a decrease in compressive strength, J-integral calculations at maximum load for the different notch root radii have indicated, particularly for the case of long fibers, a significant superiority of the reinforced material in comparison with the plain cement mortar, in consistence with the impact test data.

Compósitos poliméricos reforçados com fibras naturais da Amazônia fabricados por infusão

O desenvolvimento de compositos reforcados com fibras naturais se alia a nova logica do desenvolvimento sustentavel e potencializa a producao de materiais ambientalmente corretos. A chave para tornar economicamente viavel e ambientalmente favoraveis estes novos materiais passa pela adaptacao de tecnicas consagradas de fabricacao de compositos as propriedades peculiares e intrinsecas das fibras naturais, como o processo de infusao, que por se tratar de um processamento em molde fechado contribui para a reducao das emissoes de volateis ao meio ambiente na etapa de fabricacao. Neste trabalho estudaram-se como as principais variaveis do processo de infusao afetam as propriedades do composito quando sao utilizadas fibras naturais como reforco de uma matriz de poliester insaturado. Produziram-se placas reforcadas com fibras de curaua, juta e palha da costa arranjadas na forma de fios alinhados ou tecido em estilo plano sob diferentes niveis de vacuo no processamento. A elevacao do nivel de vacuo altera a condicao de compactacao das fibras modificando sua porosidade, interface fibra/matriz e consequentemente as propriedades do composito. Os compositos foram caracterizados quanto a sua resistencia a tracao, modulo de elasticidade, impacto Charpy e porosidade. Os resultados mostraram que o processo de infusao possibilitou a fabricacao de compositos com ate 45% de fracao volumetrica de fibra, com porosidade em torno de 2% e excelente estabilidade dimensional. Verificou-se ainda que, no geral, a elevacao do nivel de vacuo alterou significativamente as condicoes de compactacao dos reforcos, alterando, a depender da estrutura da fibra utilizada, a eficiencia da interface matriz/reforco.

Mechanical characterization of sisal reinforced cement mortar

This work aims at evaluating the mechanical behavior of sisal fiber reinforced cement mortar. The composite material was produced from a mixture of sand, cement, and water. Sisal fibers were added to the mixture in different lengths. Mechanical characterization of both the composite and the plain mortar was carried out using three point bend, compression, and impact tests. Specimens containing notches of different root radii were loaded in three point bending in an effort to determine the effect of the fibers on the fracture toughness of the material. The results obtained indicate that, while fiber reinforcement leads to a decrease in compressive strength, J-integral calculations at maximum load for the different notch root radii have indicated, particularly for the case of long fibers, a significant superiority of the reinforced material in comparison with the plain cement mortar, in consistence with the impact test data.