蚕丝包覆对碳纤维束及其复合材料电热性能的影响

Effects of silk wrapping on electrothermal properties of the carbon fiber bundle and its composites

为了进一步提高碳纤维及其复合材料的电热性能,文章采用空心锭子纺丝法制备一系列蚕丝包覆碳纤维复合丝,并采用真空模塑方法制备蚕丝包覆碳纤维复合丝/环氧树脂复合材料。通过场发射扫描电子显微镜(SEM)观察蚕丝包覆碳纤维复合丝的形貌,通过直流稳压电源和红外热成像仪探讨碳纤维束和包覆纱及其复合材料的电热性能。结果表明:蚕丝包覆碳纤维复合丝的电阻随蚕丝包缠度的增加而降低,当包缠度达到最大(包覆度100%)时,包覆纱的电阻降低了5.54%,其复合材料电阻降低了10.4%;当外加电压为2.2 V时,包缠度最大的包覆纱温度为52.2℃,相比于未包覆的碳纤维束的43.8℃增加了19.2%,同样的电压下,包缠度最大的包覆纱复合材料温度为123.47℃,比碳纤维复合材料温度(114.85℃)增加了7.5%。显示了蚕丝包覆对碳纤维及其复合材料的电热性能有显著的提升作用。

Boasting excellent mechanical and electrical properties,carbon fibers(CF),whether as a smart textile or in the form of composite materials,are expanding from national defense and military fields such as aerospace to civil fields such as automobile manufacturing.Carbon fibers are of disordered graphite structure,in which all the carbon atoms form aπbond in the same carbon ring,and all the electrons in theπbond can flow freely in this layer.Under the action of an electric field,the carbon fiber material has good conductivity due to the action of the directional movement and current.Compared with the traditional metal heating devices,carbon fibers have the characteristics of low density and good heating effect.However,due to the defects of the layered graphite structure and the inevitable wear and fracture during use,the electrothermal performance of carbon fibers has not been fully exerted,and they are easy to wear and fracture during use,which affects their application in the electrothermal field.In order to overcome this problem,many methods have been adopted to improve the conductivity of carbon fibers,especially by high-temperature treatment and doping conductive particles on the surface of carbon fibers to improve the graphitization degree of carbon fibers,and by electroplating to improve the conductivity of carbon fibers.While these methods can greatly increase the electrical conductivity of carbon fibers,all of these techniques have their own disadvantages.On the one hand,they require much energy.On the other hand,the surface treatment of carbon fibers needs to be achieved by chemical methods,and there is a risk of increasing the environmental load.As a flexible organic natural fiber,silk is composed of silk fibroin and sericin,which shows excellent properties in strength,elongation at break and energy absorption.Sericin,which is made up of amino acids,bonds to the amino groups in the epoxy to form strong bonds with the epoxy matrix more effectively than other plant fibers.In this paper,the hollow spindle spinning method was used to wrap the silk around the carbon fiber bundles to make the loose carbon fiber bundles compact and to prepare a series of carbon fiber coated yarns with different wrapping degrees,then silk/carbon fiber coated yarn reinforced epoxy composites(SCFRP)were prepared,and the electrothermal properties of silk/carbon fiber coated yarns and their composites with different wrapping degrees were studied,in order to improve the electrothermal properties of carbon fibers and their composites without increasing the content of carbon fibers.The morphology of silk-coated carbon fiber composite filaments is observed by scanning electron microscope(SEM),and the mechanical properties of the covered yarns were tested by the universal material testing machine,the electrothermal properties of carbon fiber bundles and coated yarns and their composites were investigated by means of a DC power supply and an infrared thermal imager.The results show that the electrical resistance of the carbon fiber composite filament coated with silk decreases with the increase of the silk wrapping degree.When the wrapping degree reaches the maximum(100%),the resistance of the coated yarns is 16.02Ω,with a decline of 5.54%,and the composite resistance(0.86Ω)is reduced by 10.4%.When the applied voltage is 2.2 V,the temperature of the coated yarns with the largest wrapped degree is 52.2℃,19.2%higher than that of the uncoated carbon fiber bundle at 43.8℃.At the same voltage,the temperature of the composite with the largest wrapping degree is 123.47℃,with an increase of 7.5%compared with the temperature(114.85℃)of carbon fiber composites.The contact degree between carbon fiber monofilaments can be increased by the coating of silk and the electric heating properties can be increased with the decrease of the resistance,which indicate that the electrothermal properties of carbon fiber and its composites can be significantly improved by silk coating.This provides a new idea for the application of carbon fiber and the preparation of multifunctional composites.