| Continuous carbon fiber reinforced thermoplastic polymer composites(CFRTPs)have been widely used in various fields such as aerospace,automotive,energy,petrochemical,etc.with their excellent properties.Among them,carbon fiber(CF)reinforced polyether ether ketone(PEKK)thermoplastic composites play an important role in the aerospace field because of their high toughness,excellent chemical resistance and thermal stability.Sizing agent is a key step in the molding process of composite materials,which can not only improve the surface morphology and inert structure of carbon fibers,but also act as an intermediate phase to transmit loads.In this thesis,relying on the high-strength and high-modulus carbon fiber materials developed by Ningbo Institute of Materials Technology and Engineering,Chinese Academy of Sciences,a series of matching water-soluble temperature-resistant sizing agents were developed and sizing of high-strength and high-modulus fibers was prepared into carbon fiber/polyetheretherketone composites,and the main research contents are as follows.(1)Phenolphthalein(PPL)containing a carboxyl structure was prepared by redox reaction of phenolphthalein(PPH),and then PPL and 4,4’-difluorobenzophenone were used as reaction raw materials to synthesize polyetheretherketone with a structure similar to polyaryletherketone Class sizing agent.Compared with the composites made of bare carbon fibers,the interlaminar shear strength(ILSS)increased from 24.8 MPa to 52 MPa at 1 % sizing agent concentration,an increase of 109.7 %.In addition,the tight bonding of resin and carbon fibers from the fracture morphology of the composites clearly demonstrated that the sizing agent effectively improved the interfacial properties of the composites.The reason can be attributed to the fact that the structure of the sizing agent is similar to that of PEKK resin,and the carbon fiber and resin interfaces are tightly bonded through similar compatibility,hydrogen bonding and intermolecular chain entanglement.(2)A series of water-soluble temperature-resistant polyimide sizing agents with different ratios were synthesized from bisphenol A type diether dianhydride(BPADA),m-phenylenediamine and 1,3-bis(4’-aminophenoxy)benzene(TPE-R)to sizing the surface of domestic high-strength and high-modulus carbon fibers(HMCF)and to prepare the composites.The effects of different molar ratios of composite monomers on the properties of the sizing agents and the structural properties of the surface of the fibers after sizing were investigated,and the effects of the thermoplastic sizing agents on the interfacial properties of the domestic HMCF-reinforced thermoplastic polyetherketone(PEKK)resin-based composites were analyzed.The results showed that when the molar ratio of BPADA to TPE-R composite monomer was 1:1,the synthesized thermoplastic sizing agent not only had uniform molecular weight distribution,but also had excellent thermal stability,e.g.,the thermal weight loss was only 5 % at 554 ℃.After sizing,the surface O/C of high strength and high modulus carbon fibers increased from 0.08 to 0.18,which was 125 % higher;the fiber strength increased slightly after sizing,and the modulus remained almost unchanged;the interfacial properties of the composites improved significantly after sizing,and the interlayer shear strength of HMCF/PEKK composites increased from 38.5 MPa before sizing to 59.4 MPa at the highest,which was 54.3 % higher.The interlaminar shear strength of HMCF/PEKK composite can be increased from 38.5 MPa before treatment to 59.4 MPa,an increase of 54.3 %.In this paper,based on high-strength and high-modulus carbon fibers,two sizing agents with different temperature resistance were developed to prepare for different processing needs.At present,a large number of researches on thermoplastic sizing agents are still focused on the research and development of high-strength and medium-modulus carbon fibers.With the demand for highperformance thermoplastic composite materials in cutting-edge aerospace industries,high-strength and high-modulus carbon fibers have become a development trend.Moreover,this experiment was conducted on the carbon fiber pilot line of the Ningbo Institute of Materials Technology and Engineering,Chinese Academy of Sciences,which is more reliable than small laboratory experiments.In addition,the two sizing agents not only have excellent temperature resistance,but also are water-soluble.Compared with organic solvent-based sizing agents,they are more environmentally friendly and have the advantages of low cost.They are high-strength and high-modulus carbon fiber reinforced thermoplastic composite materials.The research and development provides a new direction. |
