In order to design parts or mechanical structures made up of heterogeneous materials, composed from a polymer matrix and a natural biodegradable fiber like the ALFA, material properties of such a composite have to be known. The purpose of the present study is to propose a method for identifying the visco-elastic properties of an ALFA/PMMA composite. Unidirectional and woven composites made of the ecological ALFA fiber are studied. The properties of the ALFA fiber were determined via multiple physical tests the results of which were processed with the Weibull distribution law. Given the relaxation law of the matrix and the properties of the natural ALFA fiber, the method determines the relaxation law of the homogenized composite. To achieve that, a representative cell is chosen and then subjected to unitary displacement numerical relaxation tests. The numerical tests results are used in a non-regression identification algorithm in order to find, as a mathematical reusable form, the composite visco-elastic Prony series of the stiffness matrix components. From the stiffness matrix, using a direct and an inverse Fourier transformation, the compliance matrix is computed and the orthotropic engineering property expressions are identified. The obtained results are compared to an ultrasonic measurement test of an ALFA/PMMA 45% specimen.

Lightweight, corrosion-resistant, and longer-lasting composite materials are increasingly used as primary load-bearing materials in structures' design. The cost of rehabilitating structures is lower than that of demolishing and rebuilding them again. Therefore, economical, and eco-friendly materials could extend the life of the structures and reduce the carbon di-oxide footprint on the environment. The purpose of this paper is to present a composite hollow body that can be inserted in reinforced concrete beams. The priority was to use more economical, biodegradable, and recyclable local natural fibers. The goal is to get lighter but stronger beams. The main innovation on this work is the usage of a composite made from natural fiber. A 3D finite element model of the 5 m span beam is developed to see in detail the beam's behavior and the composite reinforcement behavior. A classical reinforced concrete beam is compared to composite shells reinforced one. As a result, the beam is lightened, the deformation is relatively reduced, the traction in concrete is reduced, and the stress in steel bars is increased but remains far from the steel's elastic limit. An experimental work was done based on 40 mm x 40mm x160 mm beams to verify the correlation of the finite element model parameters with experimental results. The results show a good correlation. The weight of the beam 5 m span beam is reduced by 26.65% without affecting its behavior. For the reinforced and non-reinforced 5 m span beams, at a similar deflexion of nearly 0.7 mm, similar stress in concrete of about 2.3 MPa and similar stress in steel bars of about 10 to 13 MPa, the maximal stress in the composite is equal to 0.460 MPa which is insignificant compared to the composite failure stress, which is about 229 MPa. The composite has a long-life and can support the efforts if the beam must be rehabilitated, for example. Consequently, lightened beams can be used in reinforced concrete structures made of non-lightened elements and have the same structural behavior.

The aging of buildings and structures, accompanied by an increase in the prices of conventional building materials, has pushed the scientific community to explore new techniques and materials to rehabilitate existing buildings. Rehabilitation aims to extend the service life of a structure while maintaining its strength and stability. Among these techniques, composite materials based on synthetic fibers, such as carbon fibers, have been developed. However, materials with low carbon footprints that are bio-sourced and eco-friendly are of interest to the scientific community. The use of Alfa plant natural stems in a braided form is the focus of this study. This study is the first to use geometric shapes to improve the performance of a natural fiber-reinforced composite. Epoxy was used as the matrix, which is the material used most often in composite designed for reinforced concrete structures. This study aims to determine the equivalent mechanical properties of the Alfa braided stem using the reverse method. Test specimens of the epoxy/Alfa composites were manufactured and tested on a tensile machine. The epoxy was tested, and its properties were determined. Subsequently, a finite element numerical model of the specimen was constructed, and the properties of the braided Alfa stem were varied until identical results were obtained. The mechanical properties of the Alfa braided stem were thus identified. The results showed that the braided Alfa stem had a stiffness modulus of 23.243 GPa.