Study On Pyrolysis Kinetics Of Carbon Fiber/Epoxy Resin Composites

Nowadays,carbon fiber reinforced epoxy resin composite materials have been used for light-small aircraft integral production,which are more and more widely applied in other fields.If the aircraft is decomposed by some thermal factors and the hazards can not be handled and responded timely,the consequences will be extremely serious.Therefore it is necessary and significant to know the pyrolysis characteristics of the composite materials.The carbon fiber bi-directional sheet,the carbon fiber unidirectional prepreg and the carbon fiber sandwich plate are typical carbon fiber reinforced epoxy resin composite materials,used for manufacturing aircrafts.The material participation,the pyrolysis characteristics and the variation laws in the pyrolysis process of the materials were experimentally investigated by thermogravimetric analysis and differential thermal analysis?TG-DTA?at different heating rates,in different morphological structure and in the different gaseous atmosphere,respectively.The three materials were tested by field emission scanning electron microscopes?FESEM?,and the morphological images magnified 1500 times were obtained.The pyrolysis residues of the three materials in the characteristic temperature of pyrolysis were tested by FESEM,respectively.The apparent activation energy was obtained by pyrolysis kinetics differential method?Kissinger?and integral method?Flynn-Wall-Ozawa?.Combined with the thermal analysis,the thermostability of the composites was studied from two aspects,including the properties of the pyrolysis and the conclusion of mathematical calculation.It can be confirmed that the interface between carbon fiber and epoxy resin matrix is the enhancement of surface bonding by the morphological images of the three materials.Through the morphological images of pyrolysis residues of the three materials,the material participation in every stage of pyrolysis process was further confirmed.Studies indicated that the pyrolysis process of composite materials were affected greatly by heating rate by TG-DTA.The initial temperature?Ti?,the final temperature?Tf?and the temperature of maximum weight loss rate?Tp?in each stage were all shifted towards high temperature with the increase of the heating rate.The pyrolysis temperature ranges were enlarged gradually.The analysis show that thermostability of the short fiber composites is weaker than that of the long fiber composites in different morphological structure.The pyrolysis mechanism of the composites is diverse under different gaseous atmosphere.Under nitrogen atmosphere,the weight loss rates of three kinds of composites were 33%,30% and 47% respectively,which were equal to the weight loss rate at the end of the second stage in the air?O₂:N₂=1:4?.Mass change leads to exothermic reaction and heat change leads to endothermic reaction in the pyrolysis of the composite materials.Combined with the apparent activation energy obtained in pyrolysis kinetics,it shows that the thermostability of carbon fiber unidirectional prepreg is the strongest and the thermostability of carbon fiber sandwich plate is relatively weak.