A facile way to modify carbon fibers and its effect on mechanical properties of epoxy composites

Here carbon fibers (CFs) was treated by silane coupling agents (KH550) and poly(amido amine) (PAMAM) in order to improve the interfacial and impact properties between CFs and epoxy resin. Tensile strength of CFs is recovered much and SEM shows the surface of CFs is significantly smooth after treatment, indicating that these macromolecules have been grafted onto CFs surface. The grafting rate of KH550 and PAMAM 3.7 wt% and 5.6 wt% is also calculated from TGA results. The mechanical properties, including stiffness and toughness, were investigated. The tests show that the interlaminar shear strength (ILSS) of KH550-and PAMAM-treated composites has an enhancement of 25.3% and 30.8% compared to that of untreated composites, respectively. In addition, impact strength of KH550- and PAMAM-treated composites is increased persistently. Then, the best mechanical properties of KH550- and PAMAM-treated CFs/epoxy composites were compared. Lastly, the improvement mechanism of mechanical properties was also explored in details, i.e., physical bonding failure, a mainly mechanical interlocking failure and chemical interaction failure for untreated, acid-treated, and molecules KH550- or PAMAM-treated CFs/epoxy composites, respectively. (C) 2020 The Authors. Published by Elsevier B.V.