Abstract
There is a lack of systematic investigations on both mechanical and electrical properties of carbon nanofiber (CNF)-reinforced epoxy matrix nanocomposites. In this paper, an in-depth study of both static and dynamic mechanical behaviors and electrical properties of CNF/epoxy nanocomposites with various contents of CNFs is provided. A modified Halpin-Tsai equation is used to evaluate the Young's modulus and storage modulus of the nanocomposites. The values of Young's modulus predicted using this method account for the effect of the CNF agglomeration and fit well with those obtained experimentally. The results show that the highest tensile strength is found in the epoxy nanocomposite with a 1.0 wt% CNFs. The alternate-current (AC) electrical properties of the CNF/epoxy nanocomposites exhibit a typical insulator-conductor transition. The conductivity increases by four orders of magnitude with the addition of 0.1 wt% (0.058 vol%) CNFs and by ten orders of magnitude for nanocomposites with CNF volume fractions higher than 1.0 wt% (0.578 vol%). The percolation threshold (i.e., the critical CNF volume fraction) is found to be at 0.057 vol%.
Highlights
Carbon nanofibers (CNFs) are electrically and thermally conductive and have very good mechanical properties
It is seen that the tensile strength increases with increasing content of CNFs until 1 wt%, beyond which the tensile strength decreases
Static and dynamic mechanical testing and AC electrical measurements are conducted to investigate the effects of CNFs on the effective properties of the CNF/epoxy nanocomposites
Summary
Carbon nanofibers (CNFs) are electrically and thermally conductive and have very good mechanical properties. Xu et al [15] demonstrated that there was only very little increase in mechanical properties of CNF/epoxy nanocomposites, ever though they used GCNF-ODA reactive linkers to improve the interface of CNFs and epoxy Because of their high electrical conductivity, CNFs have been used as fillers to improve electrical properties of polymeric composites in a number of studies [3, 4, 10, 16,17,18,19]. Other studies on electrical properties of CNF/epoxy nanocomposites did not focus on the percolation behavior, but rather on the effect of CNFs’ heat treatment [5] or on the effect of the viscosity of epoxy matrix [9] on the electrical conductivity of CNF/epoxy nanocomposites. The Young’s modulus and storage modulus were predicted using a modified Halpin-Tsai equation, which fitted the experimental results well
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