Carbon-fiber cement-based materials for electromagnetic shielding

Short carbon fiber is used as an admixture with silica fume to form cement-matrix composites. It is made from pitch or polyacrylonitrile (PAN). PAN-based fiber with a diameter of μm is effective for providing electromagnetic interference (EMI) shielding (1 GHz), low electrical resistivity (DC), and high flexural strength and modulus. Its shielding ability is superior to that of previously studied pitch-based fiber with a diameter of 15 μm (6 × 10^-4 in.). Thermally desized PAN-based fiber is less effective than the unsized counterpart for providing shielding, reflection, and low electrical resistivity, but it is more effective as a reinforcement. An increase in the fiber content increases the shielding effectiveness, decreases the resistivity; and increases the flexural strength and modulus. For each fiber content in percentage by mass of cement, the addition of sand causes a slight decrease of the shielding effectiveness; at the same fiber volume fraction, the shielding effectiveness is similar for cases with and without sand.