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- 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.