Contribution to the Characterization of Palm Kernel Shell from Littoral, Cameroon

The experimental study carried out in this work contributes to the physico-mechanical characterization of the palm kernel shells (PKS) Elaeis guineensis of the DURA and TENERA varieties. The knowledge of these properties gives an idea of their behaviour in the realization of composites and others. The absolute density was determined by the method of pycnometer, the porosity and compactness of PKS too;respectively 1428.81 kg/m3 for Dura, 1395.81 kg/m3 for Tenera;0.041 for Dura, 0.158 for Tenera;0.958 for Dura, 0.841 for Tenera. The impact energy of PKS by the pendulum sheep method has an average value of 2.066 J/cm2 and 1.894 J/cm2 for Dura and Tenera respectively at a temperature of 26°C. The longitudinal Young’s modulus of 19 GPa and 17.9 GPa for Dura and Tenera, respectively, was determined by applying the Castigliano theorem through a three-point bending test device.

Experimental and Analytical Study of Water Diffusion in Palm Kernel Shell of Cameroon

Moisture diffusion during soaking of palm kernel shell (Elaeis guineensis) aggregate concerning DURA variety of Cameroon was studied. Parameters like percentage of water gain at the saturation point and the effective moisture diffusivity were the main purposes. The knowledge of the behavior of those shells in presence of the liquid during the realization of the composite materials is important. Gravimetric method with discontinuous control of the mass of sample after immersion at the ambient temperature was used. Palm kernel shell aggregate of two origins and two considerable sizes respectively in mm: Sizes ≥ 16 and 12.5 ≤ Sizes < 16 were used. The rate of water absorption was found to be [6.18% and 11.74%] respectively for Tombel PKS and Bafang PKS and moisture diffusivity of [5.19 × 10-8 and 7.90 × 10-9 m2/s] was also determined according to their irregular shapes by fitted soaking data in Becker’s model.

Damage Evaluation of Two Equatorial Hardwoods under Uniaxial Compression: Case of <i>Entandrophragma cylindricum</i>(Sapelli) and <i>Chlorophora exelcia</i>(Iroko)

This work aims at characterizing the evolution of the damage of two tropical hardwoods. Two species from Cameroon, the Entandrophragma Cylindricum and the Chlorora Exelcia were used for the purpose. Repeated compressive loading has been made on specimens strictly selected along with longitudinal and radial directions of each species. Each cycle was made of one phase of monotonic loading and a phase of elastic release. From data obtained, we determined the variation of Young modulus and plastic deformation during each cycle of loading, and we had deduced the damage of the material. Results show that the damage appears only after a certain threshold of the plastic deformation;that damage then grows exponentially to reach a threshold after which the failure of the material occurs. As well, we noticed that the growth of damage is accompanied by the progressive decrease of the Young modulus;this confirms the deteriorating effect of the damage on the mechanical properties. Elsewhere, the damage failure threshold is less than the theoretical value, and differs from one direction to another. Finally, we noticed that the damage failure threshold of sapelli is greater than that of iroko that allows concluding that iroko gets damaged and fails more rapidly than sapelli.

Experimental Study of the Water Absorption Kinetics of the Coconut Shells (Nucifera) of Cameroun

The study is focused on the phenomenon of diffusion of water through the shells of two coconut species (coconut nucifera) of Cameroun. The kinetics absorption of water was studied experimentally by the gravimetric method with discontinuous control of the mass of the samples at the temperature of 23℃. The mature coconut shells were cleaned mechanically, cut in a spherical shape and placed in a drying oven with 105℃ for 4 hours before being plunged in distilled water at 23℃. This study made it possible not only to determine the rate of water absorbed, but also to model the water kinetic absorption of the shells. Of the two models tested (Peleg and Page), the Page model predicted very well the experimental data. The Fick law made it possible to evaluate the effective diffusivity coefficients at the initial and final phases of absorption. The effective diffusivity coefficient was given from the Arrhenius equation.

Investigating the Damaging Effects of the Cyclic Discharge in the Uni-Axial Compression of <i>Raphia vinifera</i>L. Arecacea

The bamboo stem, when mature 5 to 6 years, serves as a building material for modest houses and its marrow as packaging purposes. One of the strains related to the uses of bamboo stem is most often the compression towards the axial direction. The phenomenon of damage is very often observed during such loading. The present study on raffia aims to analyze this phenomenon through cyclical stresses as usual. From the results obtained, it was observed in the stress-strain plane, that the area of the hysteresis loops and the residual strain evolve with two parameters: the number of cycles and the stress peaks. The study of energy dissipation has shown that it evolves according to an exponential law as a function of the number of cycles. The distribution of the energy rate along a stem shows that the samples from the zone close to the base store twice (0.0412 MJ/m3) more energy than the samples taken from the top of the foliage (0.019 MJ/m3).

Experimental Study of the Drying Kinetics of the Coconut Shells (Nucifera) of Cameroon

Water diffusion of two species of coconut shells (CS) nucifera from Cameroon, in the case of drying, was experimentally studied. The experiment was done with the aid of an oven, by the method of gravimetric batch control of the mass of the test samples with the temperatures varied from 70° to 180° Celsius. The shells of mature coconuts from two species were conserved in the laboratory at a temperature ranging between 20° and 23° Celsius for two months before being mechanically cleaned. This study allows not only the determination of the water content of the shells, but also the identification of the drying model. It is thus from the ten model tests, and the statistical analysis shows that the Midilli model best predicted this drying phenomenon. The coefficient of effective diffusion was determined at different temperatures which permitted the evaluation of the activation energy per the Arrhenius equation.