The Viscoelastic Comportment of Composite Plates Reinforced with Synthetic and Natural Alfa (Stipa tenacissima L.) Fibers for Structural Applications

Composite materials are widely used in applications subjected to low, medium, and high loading frequencies. The viscoelastic behavior of these materials can significantly impact their performance and behavior under different loading conditions. As a result, it is important to carefully study the viscoelastic behavior of composite materials to design structures that can effectively withstand vibration or time-varying loads. This study investigated the static elastic, vibratory, and viscoelastic behavior of composite materials made from Carbon/Epoxy and PMMA/Natural Alfa fibers using both analytical and numerical approaches. The laminates studied included an asymmetrical laminate and an antisymmetrical laminate, both with a thickness of 2mm and composed of 9 plies. Stresses and strains were calculated for each ply and the overall composite plate. The study showed that the numerical finite element models produced results that agreed with the analytical models. The modal analysis revealed that the first frequency of the symmetrical composite [0/+45/-45/60/0/60/-45/+45/0] was 4.16Hz, which was higher than the first frequency of the antisymmetrical composite (2.61Hz) made from Carbon/Epoxy60% fibers. In terms of the viscoelastic behavior, the relaxation test of a 2mm plate showed that the stresses in the Carbon/Epoxy60% composite were stabilized quickly, while it took 20 minutes for the stresses of Alfa/PMMA45% composite plates. Alfa/PMMA45% can be a candidate for civil applications.