An Instrumented Macro-Indentation Method for Determining the Mechanical Properties of Coconut Shell (Coco Nucifera of Cameroon)

International audienceAn instrumented macro-indentation test was used to determine the viscoelastic parameters and hardness of the shell of Coco Nucifera from Cameroon in order to promote their use in the manufacture of abrasives. Samples measuring 10 mm x 10 mm x 3 mm were cut out from the bottom of the fruit, close to the natural indentations (the eye) of an approximately round-shaped fruit. The indentation load ranged from 50 to 500 N with an increment of 50 N. A comparator with digital display and a camera attached to the machine measured the total penetration and rate of penetration. The Oliver and Pharr indentation model and Hertz contact theory were used to determine the Young's modulus, hardness and creep ratio of coconut shells. Young's modulus determined in the polar zone was 3.52x10 3 MPa and 1.45x10 3 MPa in the equatorial zone. The hardness was 1.16x10 2 MPa in the polar zone and 0.7x10 2 MPa in the equatorial zone. The creep ratio was 16 in the polar region and 8 in the equatorial zone. Validation of the procedure and results will be done with indentation tests on a kind of wood: Azobé (Lophira alata). Introduction. Coconut Shell of Coco Nucifera (CSCN) is a product of the coconut tree (Coco nucifera) which is exploited for the valuable flesh (copra) enclosed in the hard shell. Important quantities of CSCN are generated during the production of copra [1]. The CSCN alone occupies about 25% by weight of the nuts and with about 54 million tons of coconuts produced annually worldwide [2], an estimated 13.5 million tonnes of CSCNs is generated. A small part of these shells is used in the production of activated carbon. [3]. However, most of CSCN is not used, presenting a challenge for solid waste management [4]. Usually the CSCN is simply discarded in nature with negative environmental impact (occupying land that could otherwise be used for agriculture, breeding sites for mosquitos). In recent years, the instrumented indentation test has been used as an alternative method for determining mechanical properties of materials [5]. The hard nature and the abrasiveness of the shell makes it a potential food processing material. A good knowledge of the properties of this hull allows it to be used as a green alternative in agro-processing tools to plump goods such as beans, maize and groundnuts, otherwise like abrasives for woods. Preliminary characterisation of this shel

Macroscopic Geometrical Modelling of Oil Palm Mesocarp Fibers of Three Varieties of Palm Nut

International audienceThis work is part of a process of characterization of plant fibers. The macroscopic geometric parameter of Oil Palm Mesocarp Fibers (length, diameter) was measured. A mathematical model of the evolution of the cross-section is provided in order to facilitate a digital reconstruction of the geometry of these fibers. In this context, we manually isolated with great care many fibers of several oil palm varieties Dura, Tenera and Pissifera distinguishing for the last two varieties two extraction position. Five different partitions of fibers have been studied. The lengths of these fibers were measured and the transverse dimensions of each of the fibers were taken at five equally spaced discrete and different sections. For each section, we made two measurements at 90 ° in the front plane and the profile view. The mathematical model of the evolution of the profile were determined in each plan and the evolution of the cross section model was described for each of the five partitions on the basic assumption that this cross section is elliptical according to SEM images and flattening rate of the cross section we calculated. Introduction. The use of vegetable fibers as reinforcement in composite materials to replace synthetic fibers is growing rapidly. Many researches are interested in it in order to optimize their physical and mechanical properties [1-5]. Many fibers (sisal, coir, raffia, jute ...) are studied in the literature [6]. The fibers from palm oil tree (EFBF 4 , OPMF 5 , OPTF 6) also have a particular interest [2, 3, 5, 7, 8]. It is clear from the various work that knowing the geometry of the fiber (section and length) is indispensable for the analysis of the results of a physicochemical characterization test (water absorption kinetic of fiber) [9], mechanical characterization (determination of Young's modulus of the fiber) [7, 10, 11] and during predictive calculations of composite properties [12, 13] (application of composites homogenization theories). All Authors are unanimous on the versatility of the geometry of the cross section and its non-uniformity along the vegetable fibers. It is shown [14-18] that the mechanical properties of sisal, jute, hemp, bamboo and coconut fiber may be influenced by the dimensions and aspect of their cross-section. Most of the works in the literature consider an approximation of vegetable fibers to a straight beam of constant circular cross section [6, 19] (in this case, the diameter measurement is made on a singular section); on the other hand, consider that the fiber is a straight beam of elliptic section and constant (measuring the major axis and the minor axis of a singular cross section) on which several measurements can be made and the average of these measurements considered as mean cross section of the fiber. Some author [11] propose a method for assessing the cross section of kenaf fibers by image analysis but this study is limited to a single sectio

Modelling of the Water Absorption Kinetics and Determination of the Water Diffusion Coefficient in the Pith of Raffia vinifera

The present work focuses on the study of the water absorption phenomenon through the pith of Raffia vinifera along the stem. The water absorption kinetics was studied experimentally by the gravimetric method with the discontinuous control of the sampling mass at temperature of 30°C. The samples of 70 mm × 8 mm × 4 mm were taken from twelve sampling zones of the stem of Raffia vinifera. The result shows that the percentage of water absorption of the pith of Raffia vinifera increases from the periphery to the center in the radial position and from the base to the leaves in the longitudinal position. Fick’s second law was adopted for the study of the water diffusion. Eleven models were tested for the modelling of the water absorption kinetics and the model of Sikame Tagne (2014) is the optimal model. The diffusion coefficients of two stages were determined by the solution of the Fick equation in the twelve sampling zones described by Sikame Tagne et al. (2014). The diffusion coefficients decreased from the center to the periphery in the radial position and from the base to the leaves in the longitudinal position

Modelling of the Water Absorption Kinetics and Determination of the Water Diffusion Coefficient in the Pith of Raffia vinifera of Bandjoun, Cameroon

The present work focuses on the study of the water absorption phenomenon through the pith of Raffia vinifera along the stem. The water absorption kinetics was studied experimentally by the gravimetric method with the discontinuous control of the sampling mass at temperature of 30 ∘ C. The samples of 70 mm × 8 mm × 4 mm were taken from twelve sampling zones of the stem of Raffia vinifera. The result shows that the percentage of water absorption of the pith of Raffia vinifera increases from the periphery to the center in the radial position and from the base to the leaves in the longitudinal position. Fick's second law was adopted for the study of the water diffusion. Eleven models were tested for the modelling of the water absorption kinetics and the model of Sikame Tagne (2014) is the optimal model. The diffusion coefficients of two stages were determined by the solution of the Fick equation in the twelve sampling zones described by Sikam

Physical and Tensile Properties of Handmade Sida rhombifolia Paper

This study focuses on the production and characterization of biodegradable handmade paper from the Sida rhombifolia plant (SRP) cellulose. Sida rhombifolia plant is a seasonal plant that grows in the equatorial and tropical climates. The studies carried out on this SRP were aimed at investigating the methods required for the production of handmade paper from SRP plant and also at determining the tensile strength. Four specimens of SRP paper of different additive labels S0 (no additive), S1 (starch and KOH), S2 (starch), and S3 (Foska liquid glue) were produced using the Kraft method. Tensile properties (stress at break, elongation at break, and Young’s modulus), the rate of water absorption, and the rate of moisture absorption were carried out. Results showed that the addition of potassium hydroxide considerably reduces Young’s modulus of SRP handmade paper (S1) while the Foska liquid glue (S3) significantly improves it. In addition, the addition of potassium hydroxide and Foska liquid substantially improves the water absorption properties of the paper S2 and S3, respectively. The adhesive liquid creates more porosity and consequently increases the absorption of water. The addition of potassium hydroxide and Foska liquid significantly embedded the rate of moisture absorption. From the results obtained, it can be concluded that the paper S3 can be used as packaging paper since it has better mechanical properties and moisture absorption

Study of Water Absorption in Raffia vinifera Fibres from Bandjoun, Cameroon

The study is focused on the water diffusion phenomenon through the Raffia vinifera fibre from the stem. The knowledge on the behavior of those fibres in presence of liquid during the realization of biocomposite, is necessary. The parameters like percentage of water gain at the point of saturation, modelling of the kinetic of water absorption, and the effective diffusion coefficient were the main objectives. Along a stem of raffia, twelve zones of sampling were defined. From Fick’s 2nd law of diffusion, a new model was proposed and evaluated compared to four other models at a constant temperature of 23°C. From the proposed model, the effective diffusion coefficient was deduced. The percentage of water gain was in the range of 303–662%. The proposed model fitted better to the experimental data. The estimated diffusion coefficient was evaluated during the initial phase and at the final phase. In any cross section located along the stem of Raffia vinifera, it was found that the effective diffusion coefficient increases from the periphery to the centre during the initial and final phases

Physical and Mechanical Characterization of Several Varieties of Oil Palm Mesocarp Fibers Using Different Cross-Sectional Assumptions

This study focuses on the characterization of plant fibers. Pressed Oil Palm Mesocarp Fibers (OPMFs) coming from different varieties (Dura, Tenera, and Pissifera) are subjected to a unitary tensile test. From the variation of strain energy, the Young’s modulus of these fibers is determined considering the evolution of the cross-section model and using Castigliano theorem. Then, we found the error made by considering first that cross-sections are circular constant and then elliptic constant. It is shown that the internal fibers have a Young’s modulus higher than those of the periphery. Moreover, the use of the real geometric model of the fiber (variable elliptical cross-section) in the search for the Young’s modulus of the fiber highlights an error that is made using the classical hypotheses encountered in the literature (circular and constant cross-section or elliptic and constant cross-section). The implementation of a Kawabata bending test also allowed us to determine the flexural modulus, the elastic recovery and the hysteresis of these OPMFs. Physical parameters such as density and linear density of OPMFs are also determined using gravimetric method

Overview of Tide Characteristics in Cameroon Coastal Areas Using Recent Observations

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