Evaluation Of The Impregnation And Tensile Properties Of The Small And Large Tow Carbon Fiber

Carbon fiber reinforced resin matrix composites have many excellent performance such as lightweight,high strength,wear resistance,corrosion resistance,electrical conductivity and so on,As a new material,Carbon fiber composites have been widely applied in aerospace,sports and leisure,bridges,roads,biomedical and other aspects.However,carbon fiber is an expensive fibrous material,Prices become a major obstacle to widespread use of carbon fiber,large tow carbon fiber can be achieved purposes of reducing the production cost,therefore,study of large-tow has great significance.In this paper,the carbon fiber STS40-48 K that produced by Toho and PANEX35-50 K that produced by ZOLTEK and other small-tow carbon fiber are used to study the performance of different tow sizes carbon fiber.The study is mainly from the following aspects:Analysis the carbon fiber surface contact angle,it was found that the initial contact angle and the stable contact angle of the large tow carbon fiber were larger than those of the small tow carbon fiber.The difference of the wettability between the large and small tows was more obvious in the infiltration process.The difference of contact angle is more than 20 °,and further confirmed that the large tow carbon fiber has poor wetting performance than small tow carbon fiber.To analysis the progress of the wetting process,we found that the infiltration process can be divided into three stages: the first infiltration stage(rapid descending stage),the second infiltration stage(slow descending stage),the third infiltration stage(flat stage).We can discover the rule: the infiltration in the first stage of the infiltration of small tow are the dominant position,the maximum variation of contact angle can be seen.The second and third infiltration stage are weak;As large tow carbon fiber,the first stage infiltration effect is weak,and the infiltration effect of second and third stage is enhanced,and the third stage of the more prominent role.The weighing method of resin content RC1,resin content section observation value RC2,porosity,apparent morphology and internal cross-sectional morphology were measured and evaluated.The results showed that the ratio of matrix content was 20%,the infiltration effect will be the best.Small tow dipping one time.Large tow dipping two times,so as to achieve the suitable content of resin.Tensile tests on carbon fiber bundle showed that with the increase of the number of monofilament in the carbon fiber tow,the strong utilization ratio Q decreased,the difference between the tensile strength and the factory tensile strength index.The tensile strength of the large tow was significantly influenced.The small tow carbon fiber has better bundle tensile strength.Through the scanning electron microscope observation of carbon fiber fracture,the fracture of wet spinning carbon fiber is smooth;dry jet wet spinning carbon fiber fracture is irregular,and in certain areas can also be observed microcrystalline broken pieces.Scanning electron microscopy observation of the bundle tensile test specimen showed that the interfacial bond between the small tow 3k carbon fiber and the resin was good,the interface was tightly bonded without fiber pull-out;The fracture of domestic 12 K carbon fiber can be seen fiber pull-out,the slip distance is short,Dongli 12 K carbon fiber can keep the interfacial bond closely with no fiber pull-out,interfacial properties of domestic carbon fiber and resin as foreign carbon fiber;carbon fiber fracture interface 24 K Dongli company produces slight debonding,fiber pull-out,maintain good interfacial bonding state;fracture of large tow carbon fiber and interfacial debonding and obvious fiber pull-out,interface the performance of large tow carbon fiber and resin than small tow carbon fiber.