Preparation And Mechanical Properties Of Non-woven Carbon Fiber/Polycarbonate Composite Materials

Carbon fiber reinforced plastic(CFRP)is a fiber reinforced composite made of carbon fiber and a resin matrix.Due to its advantages of low density,high strength,high and low temperature resistance,the CFRP has been used in aerospace,automotive,leisure sports,and other fields.At present,the CFRP mainly uses thermosetting resin as the matrix,carbon fiber woven cloth as reinforcement.After years of development,Thermosetting resin has mature technology and good mechanical properties,but there are still many shortcomings,for example,difficult to recycle,no secondary processing,poor resistance to deformation,etc.;and carbon fiber woven fabrics also have complex weaving processes,high costs and other issues.In order to overcome those shortcomings,this thesis uses polyacrylonitrile(PAN)-based non-woven carbon fiber as the reinforcement and thermoplastic resin polycarbonate(PC)as the matrix to prepare CFRP by vacuum hot pressing.The mechanical properties of composite materials prepared with T700 non-woven carbon fiber(T700F)as a single reinforcement were studied;and the mechanical properties of M50JBF/T700F/PC composite materials by adding high modulus M50 JB non-woven carbon fiber(M50JBF)and hybrid laminates of M50 JBF and T700 F were further explored.The main contents are as follows:(1)T700F/PC composite material was prepared with T700 F and PC film as raw materials,and the process conditions of vacuum hot pressing of composite material were discussed,and their mechanical properties were tested.The results show that the difference of the mechanical properties of CFRP is small under the condition of 280 ?,20 min and 1?5 MPa.When the thickness of the PC film is 0.5 mm and the volume fraction of T700 F is 30%,the tensile strength and the flexural reached the maximum,379.42 MPa and 499.75 MPa.Compared with the 15% of T700 F,they increased by 77.58%and 72.27%,respectively.Furthermore,the tensile strength is 833.06% higher than that of the pure PC.When the PC film is 0.2 mm and the T700 F is 25%,the tensile strength reaches the maximum value of 377.49 MPa,but the bending strength reaches the maximum value of 599.64 MPa,the volume fraction of T700 F is only 30%.The CFRP made of 0.2 mm PC film have better mechanical properties and improve the utilization of fibers.(2)By determining 20% of the total fiber and changing the volume fractions ratio and the stacking method of M50 JBF and T700 F,the composite materials were prepared with M50 JBF,T700F and 0.5 mm PC films and the mechanical properties were tested.The results indicate that when the M50 JBF increase from 2% to 10% and are sandwich structures(T700F/M50JBF/T700F),the tensile strength and the flexural strength decrease by 31.84% and 6.06%,and the tensile modulus increase by 42.30%.However,when the volume fractions of M50 JBF are 8%,the flexural modulus reaches the maximum value of 13.50 GPa,which is an increase of 14.50% than the minimum value.The tensile strength and flexural strength of the sandwich lamination method are higher than those of the samples with the upper and lower lamination method.The difference of tensile modulus between the two lamination methods is relatively minor.But the flexural modulus of the upper and lower lamination method is higher than the sandwich structures,and the results from the top or bottom are relatively close.(3)According to the photos of polarization microscope,the fibers in CFRP are randomly oriented in the plane,and are evenly distributed in the direction perpendicular to the plane.The surface of the M50 JB carbon fiber has a higher roughness by SEM images.But the PC resin cannot infiltrate into the fiber gap and the grooves on the surface of M50 JB due to the higher viscosity of the melted PC,which leads to poor combination of fiber and resin.Furthermore,the main failure modes for M50 JB carbon fiber are fiber breakage,fiber pull-out and debonding,and for T700 carbon fiber are fiber breakage and pull-out.Combined with the stress-strain curves,it is found that the fracture modes of the composite materials are brittle fracture.(4)The mechanical properties in all directions of the composite materials were tested.The results indicate that the two series of composite materials showed minor differences when the fiber volume fraction was 20%.The dispersion coefficient does not exceed 5%and it can be considered that the two series of composite materials have isotropic mechanical properties.