Tailoring the optical and UV reflectivity of CFRP-epoxy composites: Approaches and selected results

Specific nano- and micro-scale morphologies of composites can affect the resulting optical and UV reflectivity of the materials. One example is "Vantablack®"made from aligned carbon nanotubes (CNTs) with 99.96% absorption. A similar material with CNTs grown on surface-activated aluminum (CNTs/sa-Al) even yielded 99.995% absorption, one order of magnitude higher than Vantablack®. On the other hand, fresh snow reflects 90% or more of the incident electromagnetic radiation with wavelengths between 400 and 1,000 nm. The reflectivity of snow originates from multiple scattering in the porous morphology made of snow grains. Taking these complex morphologies as inspiration, CFRP epoxy composites with different types, sizes, shapes, and amount of nanoparticles are prepared and compared regarding their optical and ultraviolet (UV) reflectivity. Increasing the reflectivity in the near and far UV may be beneficial for the durability of the epoxy composites, but selective higher or lower reflectivity in certain wavelength ranges may also yield tailored visual effects. Results from different processing approaches with selected nanoparticles are presented and discussed.