The use of natural fibres in the development of composite materials is a sector in full expansion. These fibres were used for their low cost, availability and renewable character. The fibres of the palm (palm tree) were used as reinforcement in polypropylene. The date palm fibres have some potential because of their ecological and economic interest. Both unmodified and compatibilised fibres are used. Compatibilisation was carried out with the use of maleic anhydride copolymers. The morphology and mechanical properties were characterised by scanning electron microscopy and tensile tests. The influence of fibre content on mechanical properties of composite polypropylene/date palm has been evaluated and demonstrated that the maximum stress and elongation decreases with increasing fibre content, on the contrary, they notice an increase of the tensile modulus, but after the improvement of fibres, the maximum stress increase significantly up to 25% weight.

The objective of this work is to analyze the behavior beams functionally graded, simply supported, under different conditions such as bending, buckling, and vibration and this by use shear deformation theories a two-dimensional (2D) and quasi-three-dimensional (quasi-3D). The proposed theories take into account a new field of displacement which includes indeterminate whole terms and contains fewer unknowns, compared to other theories of the literature; by taking account of the effects of the transverse shears and the thickness stretching. In this theory, the distribution of the transverse shear stress is hyperbolic and satisfies the boundary conditions on the upper and lower surfaces of the beam without the need for a shear correction factor. In this type of beam the properties of the materials vary according to a distribution of the volume fraction, the Hamilton principle is used to calculate the equations of motion, and in order to check the accuracy of the theory used comparison is made with the studies existing in the literature.