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Improving the mechanical and physical properties of bio-composite materials involves the incorporation of plant fibers such as Jute, Hemp, Kenaf, Ramie, Sisal, Linen, etc. The existence of Diss grass (Ampelodesmos mauritanicus) in abundance in the east of Algeria especially in Khenchela region and taking into account their mechanical resistance and their low density, which justifies their choice of use in composite materials. Tensile and hardness tests for different volume fractions (from 05% to 20%) of short fibers of Diss are performed. The increase in fiber content and their treatment improves the mechanical characteristics of the composite materials. These concentration levels are added to a Polyester resin matrix. Our work relates to the study of a composite material reinforced by a vegetable fiber of which different volume ratio of short Diss fiber are considered. The results collected are purely experimental.

Blade geometry is an important design parameter that influences global wind turbine energy harvesting performances. The geometric characteristics of the blade profile are obtained by determining the distribution of the chord and twist angle for each blade section. In order to maximize the wind energy production, implying a maximum lift-to-drag ratio for each wind speed, this distribution should be optimized. This paper presents a methodology to numerically determine the change in the twist angle by introducing a range of pitch angles for the maximum power coefficient case. The obtained pitch values were distributed from the root to the tip of blade. The results prove that the power coefficient increases for wind speeds greater than the rated point, which improves the yearly production of energy by 5% compared to the reference case.

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The behavior of thermoplastics depends on several factors, mainly time and temperature. The present work is the subject of a study of the dependence of these materials on time. The material considered in this study is a polyamide 6. The applied behavior model is represented by the Kelvin-Voigt viscoelastic mechanism with instant elasticity. Following the mathematical formulation of the equations of the model, tensile tests at different strain rates are conducted. The model parameters are then identified. These being sensitive to the strain-rate, the relation which links them with it is established by means of an exponential regression. The experimental results and those obtained by the model are presented, compared and interpreted. Their relevance and coherence validates both the model and the approach adopted.