Mechanical properties of phenolic-based nanocomposites reinforced by multi-walled carbon nanotubes and carbon fibers

The mechanical properties of phenolic matrix reinforced by multi-walled carbon nanotubes and carbon fibers were investigated experimentally. The multi-walled carbon nanotubes (MWNTs) and short carbon fibers (CFs) were added to the phenolic resin to fabricate MWNTs/phenolic, MWNTs/CFs/phenolic nanocomposites and CFs/phenolic composites by hot press method. The effects of MWNT and CF contents on the mechanical properties of the composites were investigated. Modified Halpin–Tsai equation was used to evaluate the Young’s modulus and tensile strength of the three types of composites by adopting an orientation factor and an exponential shape factor in the equation. The tensile fracture surfaces of MWNTs/phenolic, CFs/phenolic and MWNTs/CFs/phenolic composites were examined using field emission scanning electron microscope. From the failure morphologies of the three kinds of composites, it is concluded that better wetting between MWNTs and the phenolic matrix than that between CFs and the matrix was found due to a larger interfacial area between MWNTs and the phenolic matrix. However, the combination of MWNTs and CFs in phenolic matrix was not mixed so well that the reinforcement effect decreased.