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- Mechanical caracterisation of polyester resin and corn natural fibers compositePublication . Queijo, Luis; Rocha, JoãoThe use of natural fibers as reinforcement in polymer matrix composites is gaining popularity in the development of renewable products. Although glass and other synthetic fiber-reinforced plastics possess high specific strength, their fields of application are very limited because of their inherent higher cost of production. The work deals with the characteristics of fiber composites that can offer several advantages, like low cost, weight savings and relatively good mechanical properties. It focuses on the effects of corn fibers as reinforcement agents in composites. Mechanical testing was performed to qualify the reinforcement properties of the corn fibers and consequently to compare with fiberglass composites.
- Mechanical caracterisation of polyester and sunflower natural fiber compositePublication . Rocha, João; Queijo, LuisThe use of natural fibers as reinforcement in polymer matrix composites is gaining popularity in the development of renewable products. Although glass and other synthetic fiber-reinforced plastics possess high specific strength, their fields of application are very limited because of their inherent higher cost of production. This work deals with the characteristics of natural fiber composites that can offer several advantages, like low cost, weight savings and relatively good mechanical properties. It focuses on the effects of sunflower fibers as reinforcement agents in composites. Mechanical testing of Sunflower natural fibers composite was performed to qualify and quantify the reinforcement properties. At same time, Glass fiber composite sample tests have been produced and characterized and both results have been compared. From results comparison we can affirm that the produced polymeric sunflower fiber composite has adequate mechanical properties for lots of industrial applications even, as expected, these are lower than glass fiber composites. Using this natural fiber content this product become a more ecological substitute and environment friendly that the traditional polymeric glass fiber composites. For other way, once stems from sunflower plants are wastes that traditionally are left in the field, shredded and incorporated in to the soil, acting like natural low cost substrate, by collecting them and giving them some commercial value will make crops more profitable.
- Optimization of hemp (Cannabis sativa L.) mechanical and physical propertiesPublication . Bueno, Guilherme Irigoyen; Ribeiro, J.E.; Costa, Roberto Germano; Rocha, JoãoNatural fibers are an alternative to the traditional synthetic fibers used for industrial applications and as reinforcement of composites material. Compared to synthetic fibers, the advantages of using natural fibers are their renewability, recyclability, low density, availability in large amounts and low cost [1]. Hemp fiber is used in many applications, it is particularly attractive to reinforcement of composites materials [2]. In this context, a mechanical and physical characterization has been made with hemp fibers grew in Bragança and Mirandela, regions from Portugal, in different conditions of nitrogen fertilization, sowing density, extraction method, and grew location. The objective of the study was to assess the effects of these parameters for optimizing the mechanical properties of hemp fibers. Tensile strength and Young's modulus were determined according to ASTM C1557 [3], density tests were made using a water pycnometer. Average value for tensile strength was 565.3 ± 167.0 MPa, average density was 1.65 ± 0.25 g cm-3 and average Young’s modulus was 92.4 ± 7.4 GPa. A statistical analysis of all parameters was made using ANOVA. The influence of all parameters was determined, the most influent parameter was extraction method and the combined effect of sowing density and nitrogen fertilization, with high influence in specific tensile strength and tensile strength, respectively. Optimal parameters for higher tensile strength were obtained for sowing density of 100 Kg ha-1, nitrogen fertilization of 50 Kg ha-1, extracted with water, cultivated in Bragança. Lower density values were obtained for sowing density of 25 Kg ha-1, nitrogen fertilization of 100 Kg ha-1, extracted with water, cultivated in Bragança. Higher Young's Modulus was determined for fibers from Bragança, with sowing density of 50 Kg ha-1, nitrogen fertilization of 50 Kg ha-1 and extracted with water.
- Experimental study on mechanical properties of hemp fibers influenced by various parametersPublication . Ribeiro, J.E.; Bueno, Guilherme Irigoyen; Martin, Manuel Rodriguez; Rocha, JoãoHemp fibers produced by different extraction techniques that were cultivated in the Portuguese districts of Braganca and Mirandela under various nitrogen fertilization and planting density conditions are examined and mechanically described in this paper. The objective of this study is to evaluate the influence of sowing density, nitrogen fertilization, sample location, and extraction method in order to improve the mechanical properties of hemp fibers. To achieve this, we determined the modulus of elasticity, the tensile strength, and the density. The mean value for the modulus of elasticity was 92.44 & PLUSMN; 7.44 GPa, the mean of tensile strength was 564.98 & PLUSMN; 167.03 MPa, and the mean of the density was 1.64 & PLUSMN; 0.24 g cm(-3). We performed a statistical analysis of all parameters using ANOVA and found that the retting method had the greatest influence among all parameters. The associated effects of nitrogen fertilization and sowing density revealed an important influence on tensile strength and specific tensile strength, respectively.
- The influence of manufacturing factors in the short-fiber non-woven chestnut hedgehog spine-reinforced polyester composite performancePublication . Ribeiro, J.E.; Rocha, João; Queijo, LuisOne of the most important agricultural products in the northeast of Portugal is sweet chestnuts. In this region only, several tons of this product are produced every year. Sweet chestnuts are enclosed in a hedgehog covered with a large number of short and fine spines and containing more than one nut. This hedgehog, with long spines, does not have any commercial value, and they are considered an agricultural waste that is left in the fields to be incorporated into the soil. In this work, the authors propose to study the influence of some factors in the short-fiber non-woven chestnut hedgehog spine-reinforced polyester composite performance. For this purpose, the tensile properties of chestnut spines were determined by implementing a design of experiments (DOE) approach developed by Taguchi. Thus, the factors that will be controlled are the fiber dispersion which is defined by fiber/matrix mass ratio or weight fraction, the interfacial strength that could be improved using an alkali–silane treatment and, finally, the moisture level in the fibers. For each factor, three levels were used, an L9 orthogonal array of experiments was implemented to evaluate tensile and flexural properties. These properties were determined based on results of 54 tests, and the maximum mean values for tensile and flexural strength were 23.5 MPa and 33.6 MPa, respectively. The most influential factor for maximizing the tensile strength was the volume fraction of fiber with a contribution of 30%, and most influential factor for maximizing the flexural strength was the moisture level with a contribution of 65%. The determined mean value of tensile strength of the spines was 148 MPa.
- New trends of additive manufacturing using materials based-on natural fibers and minerals : A systematic reviewPublication . Ribeiro, J.E.; Rodríguez-Martín, Manuel; Barreiro, Joaquín; Fernández-Abia, Ana; García-Martín, Roberto; Rocha, João; Martínez-Pellitero, SusanaPolymeric materials based on natural fibers and minerals are currently being researched and their development is still in its infancy but is expected to increase in the coming years (being nowadays a hot topic). Their main advantage is that they make it possible to use waste and by-products of agricultural, forestry, and mineral origin to generate materials for Additive Manufacturing. Since their use reduces the need for other synthetic polymers derived from petroleum and other nonnatural fibers that generate a high environmental impact, this type of material is a sustainable, environmentally friendly, biodegradable solution that can be integrated into the value chain of certain industries and, finally, favors the circular economy. This study presents a bibliometric analysis, meta-analysis, and systematic literature review focusing on plant-based fibers and minerals in biocomposites from a holistic perspective. To learn about the potential of these new materials at an industrial level and to learn about the benefits they can have for society, the strengths, weaknesses, opportunities, and threats have been evaluated. The results strongly suggest that these materials will undergo intensive development in the upcoming years, with a substantial increase in their integration across industries.
- Mechanical caracterisation of polyester and sunflower natural fiber compositePublication . Rocha, João; Queijo, LuisThe use of natural fibers as reinforcement in polymer matrix composites is gaining popularity in the development of renewable products. Although glass and other synthetic fiber-reinforced plastics possess high specific strength, their fields of application are very limited because of their inherent higher cost of production. This work deals with the characteristics of natural fiber composites that can offer several advantages, like low cost, weight savings and relatively good mechanical properties. It focuses on the effects of sunflower fibers as reinforcement agents in composites. Mechanical testing of Sunflower natural fibers composite was performed to qualify and quantify the reinforcement properties. At same time, Glass fiber composite sample tests have been produced and characterized and both results have been compared. From results comparison we can affirm that the produced polymeric sunflower fiber composite has adequate mechanical properties for lots of industrial applications even, as expected, these are lower than glass fiber composites. Using this natural fiber content this product become a more ecological substitute and environment friendly that the traditional polymeric glass fiber composites. For other way, once stems from sunflower plants are wastes that traditionally are left in the field, shredded and incorporated in to the soil, acting like natural low cost substrate, by collecting them and giving them some commercial value will make crops more profitable.