The automotive industry aims to develop high-quality engineering materials that ensure safety and optimal performance under various conditions. A critical application example is automotive headlights, whose durability and performance can be compromised by environmental and mechanical factors. To address these challenges, an alternative is proposed through the development of interpenetrating polymer networks (IPNs) of poly(methyl methacrylate) (PMMA) and polyurethane (PU), in PMMA/PU ratios of 50/50 and 80/20 [1], reinforced with 0.1% by weight of crystalline nanocellulose (CNC) obtained from disposable cups. Using experimental techniques such as Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), it was determined that the fiber processing for CNC extraction does not modify or degrade its main functional groups [2], and allows for a crystallinity percentage of 52.51% [3]. Additionally, to identify the characteristic morphologies of each polymer, confocal laser scanning microscopy (CLSM) analysis was employed, enabling the visualization of cellulose particles present. The observed fiber properties are also described, along with an analysis of cellulose dispersion within the polymer matrix and its fluorescence emission. Finally, durability is studied through tensile and compression mechanical tests, conducted before and after exposure to weathering. The results indicate less mechanical damage when crystalline cellulose is added to the PMMA/PU with a 50/50 ratio compared to a 80/20 ratio.