Matrix Decomposition of Carbon-Fiber-Reinforced Plastics via the Activation of Semiconductors

The present study proposed a novel process for the matrix decomposition of carbon-fiber-reinforced plastics (CFRPs). For this purpose, the influence of ultraviolet (UV) radiation paired with semiconductors on CFRP was analyzed. Then, suitable process parameters for superficial and in-depth matrix decomposition in CFRP were evaluated. The epoxy resin was decomposed most effectively without damaging the embedded carbon fiber by using a UV light-emitting diode (LED) spotlight (395 nm, Semray 4103 by Heraeus Noblelight) at a power level of 66% compared to the maximum power of the spotlight. Using a distance of 10 mm and a treatment duration of only 35–40 s achieved a depth of two layers with an area of 750 mm(2), which is suitable for technological CFRP repair procedures. In addition to the characterization of the process, the treated CFRP samples were analyzed based on several analytical methods, namely, light microscopy (LM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Subsequently, the prepared carbon fibers (CFs) were tested using filament tensiometry, single filament tensile tests, and thermogravimetric measurements. All analyses showed the power level of 66% to be superior to the use of 96% power. The gentle (“fiber friendly”) matrix destruction reduced the damage to the surface of the fibers and maintained their properties, such as maximum elongation and maximum tensile strength, at the level of the reference materials.