Investigation In Improvement On Interfacial Properties Of CF/EP Composite Through Introducing CNTS To The Interphase

Carbon fiber/ epoxy(CF/EP) composite is one of the most used composite in carbon fiber reinforced plastic(CFRP) and it has been widely used in various fields by virtue of excellent mechanical properties and good processability, including aerospace, civil engineering, sports goods and so on. However, carbon fibers are very brittle, bristles and breakage of monofilament are easily generated under the action of frictional force during the producing and processing. Thus, carbon fibers always are sized during industrial production because the coating of sizing agent can not only protect CFs from damaging but also increase the infiltration between fibers and resin.Besides, inert surface of CFs results in the weak adhesion between themselves with resin matrix. Carbon Nanotube(CNT) with low density and excellent mechanical properties has become an very important reinforced material in interlaminar regions of CFRP. But huge specific surface area of CNTs results in the formation of strong van der waals force among themselves, which gives rise to serious agglomeration of CNTs and then hinders itself from showing good performance in the improvement for interfacial strength of composite severely.In this paper, through a great number of comparison and verified experiments, we chose polyethyleneimine as the amine used to react with MWCNT and prepared amine-treated MWCNT successfully,where the content of N element reacted as much as 8.05%. The amine-treated MWCNT can form uniform suspension in NMP solvent as well as EP/NMP solution under ultrasound treatment, which can be strongly confirmed indirectly by the SEM results of CNT/CF fibers prepared with those suspensions. The EP/NMP solution containing amine-treated MWCNT was sizing agent exactly, which combined epoxy sizing agent and MWCNTs as a whole skillfully.Remarkably, the process of fabricating epoxy sizing agent containing amine-treated MWCNTs was so easy and we can achieve the aim of producing CNT/CF fibers continuously and massively by just sizing CCF700 with that sizing agent. Compared with unsized CCF700, sized CCF700 showed a reduction of 11.74° in its contact angle with epoxy system and improved 114.5% in its surface toughness, which resulted in a vast increase in IFSS of CCF700 composite with 77.01%.