This study analyzes the mechanical behavior of concrete beams reinforced with PET fibers, using numerical modeling in ANSYS. Four configurations were studied: beam without fibers and without notch, beam without fibers and with notch, beam with fibers and without notch, and beam with fibers and with notch. The beams were subjected to three-point bending tests, considering loading and support conditions that simulate real forces. The analysis followed the recommendations of RILEM TC 162 (2003), and the fracture parameters were determined according to the RILEM TC 89-FMT (1990) standard. The calculations involved the critical stress intensity factor (KIC), which evaluates crack propagation resistance, and the critical crack tip opening displacement (CTOD), an indicator of ductility. The simulations showed that adding PET fibers improves fracture resistance and crack control. The results highlight the potential of PET fibers as sustainable reinforcement, contributing to structural durability and the reuse of recycled materials, aligning with environmentally responsible practices in civil construction.