Preparation And Mechanical Properties Of Nano Alumina/carbon Fiber Multi-scale Reinforced Polyamide Composites

Fiber reinforced thermoplastic resin matrix composite attracts more and more interest because of its excellent mechanical properties and easier recycle.Multi-scale enhancement to further optimize its mechanical properties has become a research hotspot.Laminated film compression-molding was used to fabricate carbon fiber/nano alumina multi-scale reinforced PA6 matrix composite(CFF/Al2O3/PA6).The effect of preparation technology of prepreg,molding technology and nano-Al2O3 content on the properties of nano CFF/Al2O3/PA6 laminates were investigated by FESEM、TGA-DSC and flourier transformation infrared spectroscopy(FTIR).The results as follows:(1)The coating on the surface of CFF can be effectively removed after infiltrating CFF 24 h in formic acid solution;a good prepreg can be obtained after CFF was infiltrated by 4wt% PA6/formic acid solution for 24 h.(2)The carbon fiber reinforced PA6 matrix composite(CFF/PA6)laminates were fabricated by laminated film compression-molding to study the effects of molding temperature,molding pressure and holding time on the mechanical properties of CFF / PA6 laminates.The optimized molding process parameters are as follows: the prepressure was 1MPa and keep 10 min,and then the pressure was increased to the full pressure 3MPa and keep 15 min.The pre mold temperature was 180℃,the molding temperature was 230℃.The flexural strength,interlaminar shear strength and impact strength of CFF/PA6 laminates were 250.3MPa,87.6MPa,56.1MPa respectively.(3)With the increase of nano-Al2O3 content in the PA6 matrix,the flexural strength and impact strength of CFF/Al2O3/PA6 laminates firstly increased and then decreased.When the nano-Al2O3 content reached to 6wt%,the corresponding mechanical strength of CFF/Al2O3/PA6 laminates reached peak values,but the interlaminar shear strength decreased obviously.From the microscopic view of SEM,it can be seen that nano-Al2O3 exhibits different degrees of agglomeration.This showed that the reasonable amount of nano-Al2O3 can obviously improve the mechanical properties of CFF/Al2O3/PA6 laminates,but nano-Al2O3 was unfavorable to the interlaminar shear properties of laminates,this is related to the agglomeration of nanoparticles.(4)The addition of nano-Al2O3 particles can significantly improve the mechanical properties of composite laminates.When the nano-Al2O3 content in the matrix reached to 6wt%,flexural strength and vertical impact strength are 387.6MPa,80.3MPa,which increased by 54.8% and 94.9%,respectively,when compared with CFF / PA6 laminate.