Resistance welded thermoplastic composites joint strengthened via carbon nanotubes from flame: interface strength, mechanical properties and microstructure

Abstract

Carbon nanotube (CNT)-grafted carbon fibers (CFs) were used as the interlayer heating element for resistance welding of glass fabric reinforced polyetherimide (GF/PEI) composite laminates to enhance the strength of the joints of GF/PEI. The effects of CNTs on the wettability of PEI resin on the CF surface and the interfacial microstructure and mechanical properties of welded joints were investigated. The CNTs were grown in situ on the surface of the CFs by a flame method, and their structures and morphologies were characterized by Raman spectroscopy, scanning electron microscope (SEM) and transmission electron microscope (TEM). PEI resin solution exhibits better wettability on CNTs-grafted CF surface with the help of capillary action. The interfacial shear strength (IFSS) of the CF/PEI resin and the SEM images of the bonding interface show a stronger binding effect between CNTs-grafted CFs and PEI resin. The mechanical property of the joints was evaluated by the tensile test of single lap shear strength (LSS). The LSS values increased first and then decreased with welding time (tw), and the optimum LSS of the joint with CNTs was increased by 23.6% to 32.5MPa in comparison with that of the joint without CNTs when tw was 60 s.