Research On Laminates For Continuous Carbon Fiber Reinforced Polyether Ketone Ketone

Continuous carbon fiber reinforced polyaryl ether ketone?CF/PAEKs?composites have the advantages of high specific strength,high specific modulus and excellent corrosion resistance,which have attracted extensive attention from the researcher.Among them,carbon fiber reinforced polyetherketoneketone?CF/PEKK?composites have the advantage of good biocompatibility,mechanical properties,excellent resistance to humidity and heat aging,high temperature resistance,and recyclability,which are used in medical,aerospace,oil extraction and other fields.Hence,it has significant application prospects and economic worth for researching of continuous CF/PEKK laminates as one of the terminal products.In this paper,the continuous CF/PEKK prepreg tapes were prepared by the powder impregnation process using the experimental equipment designed and assembled by the research group.The effects of process parameters of different tension,fiber content and heat treatment on the size and performance of the prepreg tapes were studied.Continuous CF/PEKK laminates were prepared by hot press molding process.The mechanical properties of the composite laminates under different molding conditions?temperature,pressure,holding time?were tested to determine the optimum process parameters for the preparation of the laminates.Finally,the mechanical properties?flexural strength,tensile strength,interlaminar shear strength?,dynamic mechanical behavior,melting and crystallization behavior,thermal stability and damp heat aging properties of composite laminates were systematically investigated.It provided a reference for the actual production and application of continuous CF/PEKK laminates.The main finding are as follows:?1?CF/PEKK prepreg tapes were prepared by wet powder impregnation process.The effects of fiber content,tensioning force and CF heat treatment on prepreg tapes were studied.When the prepreg fiber content was 74 wt%,the tensile strength of the prepreg tapes reached 1934.08 MPa,which was 21 times that of PEKK resin.The tensile strength was greatly improved,because of CF acting as a load bearing member in the composite.As the tension increased,the width and tensile strength of the prepreg tapes increased to a maximum at a tension of 14 N.As the tension increased,the fibers were gradually straightened while increasing the friction between the fibers and the mold,so that the fiber gap became larger and the width increased,which facilitated the impregnation of resin and fiber.The heat treatment of CF in advance can increase the width of the prepreg tapes,but had little effect on the tensile strength.?2?Continuous CF/PEKK laminates were prepared by hot press molding,and the effects of process conditions on the mechanical properties of the composite laminates were investigated.The results show that when the molding pressure was5 MPa,the temperature was 350°C,and the holding time was 20 min,the preparing 0°ranking laminates had smooth surface and excellent mechanical properties.And the flexural strength reached 2050.27±50 MPa and flexural modulus was 115.34±10 GPa,interlaminar shear strength was 78.14 MPa.By testing the properties of the laminates at different fiber contents,it was found that when the fiber content was 65 wt%,the tensile strength of the laminates was the largest.When the fiber content was too higher,the resin had a small bonding force and was prone to delamination.By testing the performances of composite laminaties with three different prepreg tapes ranking modes?weaving,0°/90°,0°?,the 0°ranking of the laminate had the best mechanical properties,which was due to the direction of the force.The CF content was large and played a role of mainly bearing the load.?3?The thermal performance tests show that,the load deformation temperature of composite laminates were above 250°C,which had good high temperature resistance.When the temperature was at 476°C,the rein structure was destroyed and decomposed.At 545°C,the rein decomposition rate was the fastest.At 700°C,the mass retention rate of the composite laminate was 83.75%.It fully demonstrates that the continuous CF/PEKK laminate had good thermal stability.?4?Differential scanning calorimetry?DSC?tests show that,the cold crystallization temperature?T_c?of the PEKK material moved to high temperature and the melting point?T_m?decreased after the addition of CF.This was because CF hindered the movement of the PEKK molecular chain during the cooling crystallization process,resulting in imperfect crystallization and decreasing melting point.During the heating melting process process,CF restricted the movement of the molecular segments,and the rearrangement of the molecular segments required higher temperatures,so the composite laminate T_c was higher.?5?The dynamic mechanical behavior?DMA?test show that,the storage modulus?E??of the composite laminate was higher at 65 wt%fiber content,which meant that the material had strong resistance to external force deformation.Compared to the 0°/90°laminate,the E?of the 0°laminate was higher because the fiber was subjected to load in the direction of the alternating stress,so the material exhibits rigidity and E?was higher.?6?The tests of damp heat aging show that,the overall performances of the laminaties under the four conditions had declined,and the flexural strength of the laminates was most significant under the condition of 70°C H₂O.This was due to the accelerating movement of water molecules in a high temperature environment,which makes it easier enter into the interior of the composite,resulting in debonding of the resin from the CF.At this time,the laminate strength retention rate was 72.98%,which still had a high strength.Therefore,the CF/P EKK laminate has excellent heat and humidity resistance.