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This work aims to develop analytical and numerical approaches for predicting the water diffusion through raffia vinifera pith using Fick’s law. A representative elementary volume consisting of a fiber surrounded by a layer of natural matrix is considered. Assuming that the physical properties of fiber and matrix are constant, the resulting equations are solved analytically by the separation of variables method and numerically by finite difference method. A constant water concentration is imposed at the external surface of material while the continuity of the moisture and flux is applied at the fiber/matrix interface. To test the computational results, physical properties of the two layers are set equal. The experimental solutions in this case are used as the reference results, and the present computational method results are compared. Results demonstrate that the maximum value of the relative error is less than 6.5% for numerical and 11% for analytical methods. The case of two layers with different physical properties is examined. Results indicate that the heterogeneity of raffia vinifera pith reduces considerably the water absorption in the fiber. This study can be applied to composite materials where the polymers are combined to natural fibers to achieve high mechanical properties of materials.

This work focuses on the optimal design of the woven fabrics made from Raphia vinifiera, fiber, and their contribution as reinforcing element in the epoxy matrix. The work is done alternately experimentally and theoretically. The woven made of canvas, twill and satin armor are characterized in traction according to the ISO13934-1 standard [1]. A predictive mathematical model of Young's modulus of the woven with the greatest rigidity is established. The woven reinforcement composite made is characterized in traction and bending according to EN ISO 527-5 [2] and NF EN ISO 14125 [3] standards. In order to determine the reinforcement rate which gives the highest young modulus of the material, the gradient method was applied on some prediction equations of Young's modulus of composite material. Then find the prediction equation that best corresponds to the composite made. The results showed that mathematical modeling works corroborates with experimental works. On the woven fabrics the canvas armor has the highest Young's modulus in the warp and weft direction (2.429, 21.164 GPa). Followed by twill (2315, 18 741 GPa) and satin (2184, 18.54 GPa). On the composite, the reinforcement rate from which the material is optimized is 50%. The composite young's moduli in the warp and weft direction resulting from the tensile and bending tests of the composite are respectively (3.644, 7.31 GPa) and (1.802, 4.52). In a nutshell, this work presents the theoretical and experimental aspect of the best material which can be obtained with R. vinifiera fiber with respect to its Young modulus.

The objective of this work is to investigate the physico-chemical properties of agro-industrial by-products in order to determine some potential valorization applications in composites materials. Four different by-products have been studied: coconut nucifera shells, canarium schweinfurthii fruit cores, palm kernels shells and raffia vinifera fruit cores. The chemical composition of the materials was studied by Fourier transform infrared spectroscopy (FTIR). It made it possible to identify the presence of chemical compounds characteristic of biosourced materials such as cellulose, hemicellulose and lignin. The thermal properties were determined by thermogravimetric analysis (TGA), in order to determine the moisture content, the thermal degradation temperatures and the ash content of the biosourced materials. The results show a first phase with a loss of mass corresponding to the evaporation of water, with humidity contents varying between 7 and 10%. The second phase corresponds to the decomposition of cellulose and hemicellulose, starting between 185°C and 225°C. After the third phase of degradation, corresponding to the decomposition of lignin, the ash content is determined. The surface properties of the materials were also studied by wettability measurements. The contact angles of water (polar liquid) and diiodomethane (non-polar liquid) were measured. The surface energies could then be calculated, and vary between 54 and 65 mN/m. A correlation between the wettability and TGA results has been evidenced, the higher content of lignin inducing a lower surface energy, and potentially a better compatibility with polymer matrix. The targeted applications concern the use of these biosourced products as abrasive composite materials (associated with a polymer matrix), for example in the shoe industry (for the machining of soles), and also in mechanical stripping of surfaces. [ABSTRACT FROM AUTHOR]

Copyright of Cameroon Academy of Sciences Journal is the property of Cameroon Academy of Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study evaluates the effects of lengths and reinforcement ratio of Raphia vinifera fibres (RVFs) on the physical and mechanical properties of an epoxy matrix composite. Three volume fractions (20%, 30%, and 40%) and three lengths (5, 10, and 15 mm) of fibres were used to produce the composite, and the samples were subjected to the absolute and apparent density, porosity, water absorption rate, and tensile and flexural strength. The probability of failure of the composite is described by the means of two-factor Weibull model. In addition, a theoretical approach to predict mechanical characteristics based on empirical models was carried out. The results show that the addition of RVF decreases the density of the composite, while the porosity and absorption rate increase. The mechanical test shows that the tensile and flexural stress and Young's modulus of the composite are lowered compared to those of the resin alone. Multivariate analysis of variance (MANOVA) and Tukey test showed that fibre lengths and reinforcement ratio significantly lower the mechanical properties of the composite. The distribution of strength and Young's modulus follows Weibull's law. Furthermore, the Cox–Krenkel mathematical model has the best approximated model for the experimental results after the tensile test. Based on these results, this material could be used as reinforcement parts for vehicle backrests or interior decoration in the construction industry. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Natural Fibers is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Natural Fibers is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Natural Fibers is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This work focuses on the assessment of oil palm mesocarp fibers as reinforcement in a composite material with an unsaturated polyester matrix. Several volume ratios of OPMF reinforcement (0 to 15%) were used, the fibers being distributed randomly. The resulting composite was characterized on the physical and mechanical aspects. Physically, the true and apparent densities were determined as well as the porosity rate. It appears that the addition of fibers further lightens the composite and increases the porosity. The water absorption rate of the different composites samples was evaluated. The more fibers the composite contains, the higher its water absorption rate. On the mechanical aspect, the bending modulus of elasticity, bending stress at break, and breaking strain were evaluated through a three-point bending test on all combinations. The same parameters were also evaluated for certain combinations by a unidirectional tensile test. It appears from this mechanical characterization that the volume fraction of 5% reinforcement has the highest specific modulus. Impact tests were performed on samples of this combination using several sizes of reinforcing fibers. Impact resistance is enhanced as the size of the inclusion increases. The Halpin-Tsai micromechanical model for randomly distributed short fiber composites was used for the inverse approach determination of the theoretical moduli of the matrix and OPMF, then in a direct approach to determine the elastic modulus of the composite at 7.5% reinforcement. [ABSTRACT FROM AUTHOR]

This work focuses on the optimal design of the woven fabrics made from Raphia vinifiera, fiber, and their contribution as reinforcing element in the epoxy matrix. The work is done alternately experimentally and theoretically. The woven made of canvas, twill and satin armor are characterized in traction according to the ISO13934-1 standard [1]. A predictive mathematical model of Young's modulus of the woven with the greatest rigidity is established. The woven reinforcement composite made is characterized in traction and bending according to ENISO527-5 [2] and NF EN ISO14125 [3] standards. In order to determine the reinforcement rate which gives the highest young modulus of the material, the gradient method was applied on some prediction equations of Young'smodulus of compositematerial. Then find the prediction equation that best corresponds to the composite made. The results showed that mathematical modeling works corroborates with experimental works. On the woven fabrics the canvas armor has the highest Young's modulus in the warp and weft direction (2.429, 21.164GPa). Followed by twill (2315, 18 741GPa) and satin (2184, 18.54GPa). On the composite, the reinforcement rate from which the material is optimized is 50%. The composite young's moduli in the warp and weft direction resulting fromthe tensile and bending tests of the composite are respectively (3.644, 7.31GPa) and (1.802, 4.52). In a nutshell, thiswork presents the theoretical and experimental aspect of the bestmaterial which can be obtained with R. vinifiera fiber with respect to its Young modulus. [ABSTRACT FROM AUTHOR]

In an industrial context where the use of friendly materials is encouraged, natural fibers of vegetable origin become more solicited for the reinforcement of composite materials. This work deals with the modeling of the hygro-mechanical behavior through raffia vinifera fiber during the diffusion phenomenon. The modeling of water diffusion through the raffia vinifera fiber is described by Fick's second law and taking into account the swelling phenomenon of the fiber. The equation obtained is solved numerically by the finite difference method, and the evolution of the fiber radius as a function of time is obtained. By applying the Leibniz integration rule, a mathematical expression to predict the evolution of this radius as a function of time is proposed. It is observed numerically and analytically an increase of the dimensionless fiber radius with time up to a critical value after what one observes the saturation. This model allowed us to propose a mathematical model describing the absorption kinetics of the raffia vinifera fiber through its absorption ratio. By comparing the results of this model with the experimental results from the literature, one observes a good agreement. Moreover, the induced stresses in the fiber during the water diffusion can also be estimated with the proposed mathematical model expression of fiber. These stresses increase with time and can reach between 5 and 7 GPa. The results of this work can be used to predict the behavior of the raffia vinifera fiber inside a composite material during its development. [ABSTRACT FROM AUTHOR]