Valorization of the use of natural Alfa (Stipa tenacissima L.) fiber in composite reinforcing plates based on natural fibers and metal fabric

摘要

Composites are used to reinforce existing structures to remedy current pathologies or increase their loading capacity to resist loads higher than initially envisaged by the calculations. The most commonly used composites are carbon fibers. However, due to their high cost, their use is still limited. In contrast, using natural fibers embedded in plastic matrices could provide an economical and ecological solution because they incorporate recyclable fibers and materials. This study investigates the reinforcement of concrete beams with lightweight composite plates reinforced with treated natural Alfa fibers. The proposed composite reinforcing plates comprise an epoxy matrix reinforced with randomly oriented short fibers and metallic fabric. The metallic fabric increases the beam's moment resistance by moving the steel's centroid downwards. It also increases the stiffness of the composite and, therefore, reduces its deformation. Several layers could be added to obtain the desired stiffness; however, only one layer was considered in this study. Various specimens were subjected to four-point bending tests, obtaining satisfactory experimental results. The beams with dimensions of 4 x 4.2 x 50 cm and reinforced with an 0.8 cm Epoxy/Alfa10% composite plate resisted a maximum load of 1.5 kN before failure. The control beam, with dimensions of 4 x 5 x 50 cm, failed at 1 kN. Furthermore, the beam reinforced with an Epoxy/Alfa10% composite plate containing a metallic fabric failed at a force of 1.7 kN, exhibiting the best behavior. Several phases were observed during the damage evolution, starting with the appearance of the first crack in the concrete, continuing with the development of multiple cracks in the central part subjected to pure bending, and ending with the failure of the composite. Finally, the experimental results were compared and correlated with those obtained with finite element models during the first loading phase until the appearance of the first crack in the concrete.