| Compared with traditional metal bolts,carbon fiber reinforced polypropylene resin composite(CF/PP)bolt fasteners have excellent properties such as low density,acid and alkali corrosion resistance,and convenient processing.Under the premise of ensuring the reliability of bolt fasteners,replacing high-density metal with low-density CF/PP,and preparing lightweight and high-strength composite bolt fasteners by injection molding is one of the important technical means for the development of lightweight automobiles.one.However,due to the poor interfacial bonding of carbon fiber and polypropylene resin,this has become one of the main factors limiting the improvement of mechanical properties of CF/PP bolt fasteners.Therefore,in order to improve the mechanical properties of CF/PP bolts,it is proposed to use carbon fibers with better interfacial properties of polypropylene to improve the mechanical properties of CF/PP bolts.In this paper,low-cost recycled carbon fiber reinforced polypropylene composites(rCF/PP)are used to prepare bolt fasteners.One of the reasons for the poor performance is that the interface properties are defective,so the sizing carbon fiber is used to improve it.In this paper,the pulp of polypropylene resin and the T300 grade carbon fiber of epoxy-based pulp are selected as the research objects,which are provided by Taiwan T Company and Lianyungang Z Company respectively.By comparing the appearance,tensile properties,infrared spectrum and other characteristic properties of the two carbon fibers,the influence of the surface physical properties of the fibers on the interface of the composite material was analyzed.The basic parameters such as density,carbon fiber volume fraction,fiber remaining length,and mechanical properties of the two CF/PP composite injection molded parts were tested,and the combination of fibers and resin in the samples after tensile fracture was observed under scanning electron microscopy(SEM).,and further analyze the interfacial bonding properties of two carbon fibers and polypropylene and the relationship between interfacial properties and mechanical properties.It provides a theoretical basis for the optimization of the raw materials of bolt fasteners,and lays a foundation for the preparation of CF/PP bolt fasteners that meet the performance requirements.The following are the conclusions of this experiment:(1)The density of rCF/PP injection-molded bolts is lower than that of ordinary metal bolts,but the mechanical properties such as tensile,bending,and torque of the former are inferior to those of the latter.Among them,the tensile strength of rCF/PP injection-molded bolts only reaches the lowest level.Grade(grade 3.6)common metal bolt level.Through the research on the micro-morphology of rCF/PP bolts,it is found that the interface bonding performance of recycled carbon fiber and polypropylene resin is not good,which leads to the poor transfer effect of stress between fibers and resin,which ultimately limits the rCF/PP bolt fasteners.The improvement of mechanical properties.(2)As far as the properties of CF-TC(Taiwan company carbon fiber)and CF-SY(Lianyungang Z company carbon fiber)are concerned,since the two carbon fibers are both T300 grades,there is almost no difference in the mechanical properties of the fiber monofilament.However,due to the wet spinning process of CF-TC,the surface of carbon fiber is rough and has a groove structure.In addition,the CF-TC surface sizing agent is mainly aimed at polypropylene resin,so the surface characteristics of CF-TC are different from CF-SY,which is more helpful to improve the bonding effect of carbon fiber and resin matrix.(3)Due to the difference in the surface characteristics of carbon fibers,the bonding between fibers and resins will be affected,thereby affecting the mechanical properties of carbon fiber composites.Among them,the tensile modulus,tensile strength and elongation at break of CF-TC/PP are increased by 19.60%,23.75% and 61.54% respectively compared with CFSY/PP;the flexural modulus and flexural strength are higher than CF-SY/PP.increased by17.12% and 34.81%;but the impact properties of the two composites are not much different.It can be seen from the tensile cross-sections of the two that the fiber and resin in the CF-TC/PP composite have better overall bonding and better interface properties. |
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