Navegando por Assunto "Fibras naturais"

Agora exibindo 1 - 4 de 4

Acesso aberto (Open Access)
Análise experimental de vigas de concreto armado reforçadas à força cortante com compósitos de fibra de juta, carbono e vidro utilizando a técnica EBR
(Universidade Federal do Pará, 2022-10-18) MACIEL, Luciana Pereira; BANNA, Wassim Raja El; http://lattes.cnpq.br/2005046563115507; https://orcid.org/0000-0001-5085-4352; LIMA NETO, Aarão Ferreira; http://lattes.cnpq.br/0287664572311345; https://orcid.org/0000-0002-5911-1368
The application of FRP (Fiber Reinforced Polymer) with the EBR (Externally Bonded Reinforcement) technique for repairing and reinforcing structures stands out due to the low density of the material and ease of application. In this case, the use of synthetic fibers is common, however, these fibers are considered inaccessible and harmful to the environment. This disadvantages raised studies on the replacement of synthetic fibers by natural fibers. Therefore, this work consists of the experimental analysis of the performance of composites of jute fibers as shear reinforcement. With that aim, seven reinforced concrete beams reinforced with FRP's were molded using the EBR technique, they were dimensioned with greater flexural strength in relation to the shear force and with transverse reinforcement positioned only in a section of the span, to induce shear failure in the region without stirrups. The beams are 2 meters long and have a cross section of (15x20) cm. One beam was not reinforced, to be used as a reference, one beam was reinforced with one layer of FRP with carbon fiber, one beam with two layers of FRP with glass fiber, two with hybrid FRP of layers of glass and jute fiber with three and four layers, and finally two beams with jute fiber FRP with two and three layers. The reinforcements were applied in strips along the length of the shear span of the elements, perpendicular to the axis of the beams, U-shaped. It was observed that the reinforcement with two layers of jute fiber presented a 48% increase in shear force of the beam in relation to the reference beam, this result was similar to that observed in the beam reinforced with one layer of carbon fiber. Other positive behaviors were observed in the other reinforced beams, such as cracking control, increase in maximum shear force and containment of vertical displacement in relation to the reference beam. The experimental results were compared to theoretical results calculated according to ABNT NBR 6118 (2004), ACI 318 (2014), Eurocode 2 (2004), ACI 440.2R (2017) and fib 90 (2019). After analysis, the initial results of this research demonstrate the viability for other in-depth studies on the use of jute fibers in shear reinforcement of reinforced concrete beams.
Acesso aberto (Open Access)
Avaliação microestrutural e mecânica das fibras de cotia e dos compósitos de matriz poliéster
(Universidade Federal do Pará, 2025-01-20) NASCIMENTO, Damares da Cruz Barbosa; OLIVEIRA, Michel Picanço; http://lattes.cnpq.br/6383844066460475; https://orcid.org/0000-0001-9241-0194; CANDIDO, Verônica Scarpini; http://lattes.cnpq.br/8274665115727809; https://orcid.org/0000-0002-3926-0403
The search for sustainable and low-cost materials has driven the use of natural fibers in the development of polymer composites, due to their mechanical and sustainable properties. The aim of this work is to study and characterize a new natural fiber, as well as to study the mechanical properties of composites made with in natura fibres (FC) and mercerized fibres (FM) in volumetric percentages of 10, 20 and 30%. The fibres and composites were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Thermogravimetry (TGA), Scanning Calorimetry (DSC), Energy Dispersive Spectroscopy (EDS) and Raman Spectroscopy, as well as mechanical characterization. The physical characterization of the fiber indicated an average density of around 0.34 g/cm3. The FTIR of the FC and FM fibers indicated chemical structural changes, which were confirmed with Raman, SEM and EDS. The thermal stability of Cotia fiber in natura was close to 145 and 272 ºC. The mechanical properties of the FC and FM fibers showed average strengths of around 151.32 and 99.98 MPa, respectively. The FTIR and Raman scans of the composites showed few changes related to the variation in chemical treatment, but differences when percentages of fibers were added. The tensile and flexural results indicated that the CF fibers were stronger and stiffer in relation to the matrix than the modified fibers. The SEM confirmed the existence of defects and flaws that caused early rupture of the composites with FM fibers. The single and double F ANOVA confirmed that both factors, chemical modification and increase in volume percentage, had an impact on the final properties. Although the results of the FM fibers did not have a positive impact, the properties of the in natura fibers stand out as efficient reinforcements for engineering applications.
Acesso aberto (Open Access)
Caracterização do tecido fibroso de tururi e avaliação de propriedades mecânicas de compósitos de matriz poliéster reforçados com tecido fibroso de tururi
(Universidade Federal do Pará, 2023-01-30) SANTOS, Avener Gleidson Andrade; CÂNDIDO, Verônica Scarpini; http://lattes.cnpq.br/8274665115727809; https://orcid.org/0000-0002-3926-0403
In recent decades, the search for materials with high mechanical performance and that are in accordance with sustainability requirements has become increasing. In the context of sustainability, the United Nations (UN) established in 2015 the Sustainable Development Goals (SDGs), in order to guide the paths to sustainable development. The use of waste to produce new materials is beneficial, because the use of these materials represents a solution for environmentally friendly disposal, thus covering the requirements established by the SDGs. The use of natural fibers in the production of new materials has increased significantly in the last decade. The use of natural fibers as reinforcement in polymer matrix composites is already well established. This is due to the fact that some fibers have high mechanical performance and good thermal stability, two highly attractive properties in composite materials. Composites reinforced with natural fibers have a vast field of application, and can be used in civil construction, aerospace, and automotive industries, among others. In this scenario, the use of tururi fabric as a reinforcement agent in composites of polymeric matrix emerges as a viable alternative for sustainable disposal of this waste coming from the harvesting stage of its fruits. Thus, this study aims to characterize the tururi fibrous tissue by optical microscopy, scanning electron microscopy, X-ray diffraction, thermogravimetric analysis and Fourier transform infrared spectroscopy (FTIR), as well as to determine physical properties such as density, moisture content and weight. The composites were produced using a 2.5, 5.0 and 7.5% by mass percentage of reinforcement. Additionally, tensile, flexural and charpy impact tests were performed. The characterizations revealed that the tururi fibrous tissue is composed of fibers of various diameters and has regions of bifurcation, indicating that the tissue can act in different ways when incorporated as reinforcement. The density, moisture content and weight had average values of 1.17 g/cm3, 16.58% and 146.61 g/m2, respectively. The thermal analysis revealed good thermal stability for the tururi fabric. The mechanical tests pointed out that as the incorporation of reinforcement occurred, the composites tested in traction had a loss of resistance, presenting a loss of 15MPa in relation to the matrix. When requested in flexion the composites reinforced with up to 2.5% showed better mechanical performance, with values of 63.9 MPa. The impact test revealed that the energy absorption capacity increased by 371% compared to the matrix, which indicates that the fabric acted as a good reinforcement agent.
Acesso aberto (Open Access)
Fibra de curauá como reforço em matriz cimentícia para fabricação de telhas e placas de fibrocimento
(Universidade Federal do Pará, 2015-11-03) SALES, Cintia Gama; PICANÇO, Marcelo de Souza; http://lattes.cnpq.br/4535052395600357
Natural fibers such as reinforcing fragile matrices based on cementitious materials, have attracted great interest in developing countries, because of its low cost, availability, energy saving. The use of composites in plates, roof tiles and prefabricated components, can make a significant contribution to the rapid growth of infrastructure in developing countries. Among the natural fibers, curauá fiber, Ananas erectifolius, has gained prominence because of its high tensile strength. The main objective of this work is the use of curauá fiber as reinforcement matrix with Portland cement, for use in structural elements such as slabs and tiles. For this study, testing and compression modulus of elasticity in mixtures with a volume fraction of 1% and 2.5% and fiber length of 1 cm and 2 cm, and full mortar without fibers were performed. The mixture showed the best results in terms of workability, was the volumetric fraction of 1% and 1 cm fiber length, was chosen for the manufacture of cement tiles and plates. For the evaluation of composites was conducted tensile strength test in bending the plates and tiles with curauá fibers and no fibers, for comparison. The results confirmed the influence of the fibers on the composite deformation capacity increasing by 46% the tensile strength in plate bending with curauá fiber relative to the plate without fiber, and increased tile breaking load of 49% with respect to tile without fiber.