The study explores how dyes can improve the strength and optical properties of composites made from flax seed fiber and epoxy, which are incorporated with biosynthesised TiO2 nanoparticles derived from the Curcuma longa plant. The TiO2 nanoparticles were produced using a synthesis method that involved curcumin from Curcuma longa as a reducing and stabilizing agent. By introducing dyes to these composites, it enhances the bonding between layers. Optimizes their ability to absorb UV light. The research findings analyze how the ILSS (interlaminar shear strength) improves by adding natural dye additives and measurable enhancements in their optical characteristics. The results indicate that composite materials containing 5 wt% of nanoTiO2 exhibit the ILSS value (52.31 MPa). This is because the TiO2 particles are evenly distributed throughout the substance at this concentration. The crystal orientation and size (71.02 nm) of biosynthesized TiO2 nanoparticles were determined using X-ray diffraction techniques. Regarding optical properties, observations were made across a wavelength range of 450–2300 nm. Compared to a surface, it was observed that incorporating dyes into adsorbents led to increased absorption and reduced transparency across light wavelengths. This study offers insights into the uses of composites infused with natural dyes in sustainable engineering and materials that protect against sunlight.