Top-down digital light processing 3D printing of composite structures using carbon fiber modified UV curable resin

Utilizing the shear-thinning property of carbon-fiber modified resins, composite structures were fabricated by digital light processing (DLP) 3D printing. The rheological behaviors of the resins were studied with different loading ratios of carbon fibers. Curing kinetics of the resins were analyzed using Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR). The effects of different carbon fiber loading ratios on the mechanical and thermal properties of the fabricated structures were investigated by tensile testing and thermal gravimetric analysis (TGA). It was found that the Young's modulus and tensile strength first showed a monotonic increase with an increasing carbon-fiber loading ratio up to 7.5%. However, when the loading ratio was further increased to 10.0%, the mechanical strengths of the fabricated parts decreased. Specifically, with a 7.5% weight percentage of carbon fibers in the resin, an improvement factor of 536% in Young's modulus and 323% in ultimate tensile strength was obtained in the resultant 3D printed parts. Additionally, the weight loss analyzed by TGA suggested that incorporating carbon fibers in the UV curable resin can help enhance the thermal stability of the fabricated parts. Models made of unmodified resin and carbon fiber-modified resin were tested for vulcanizing applications, in which the 3D printed models were embedded in rubber to form shape-complementary cavities under high temperature and high pressure. Casting pieces resulting from the models printed with carbon fiber-modified resin showed dramatically improved surface quality. The improvement in the casting performance was attributed to the enhancement in the thermal and mechanical properties caused by the addition of carbon fibers.