Study On Combustion Characteristics Of Epoxy Resin/carbon Fiber Composites

Epoxy resin/carbon fiber composites are widely applied to the field of aviation and aerospace.Since it's epoxy resin matrix is mostly combustible,it will release a great amount of heat and toxic smoke with the mechanics capability degradation of epoxy resin/carbon fiber composites when exposed to the conditions of high temperature or fire,which will bring a serious threat to people's life.In this paper,three typical carbon fiber/epoxy composites(carbon fiber bidirectional sheet,unidirectional carbon fiber prepreg and carbon fiber sandwich plate)of small electric aircraft and it's epoxy resin matrix were used as the research object.The combustion performance of epoxy resin matrix,carbon fiber bidirectional sheet,unidirectional carbon fiber prepreg,carbon fiber sandwich plate and epoxy resin matrix were tested under different fire conditions using cone calorimeter,horizontal vertical burning tester,high temperature oxygen index.The change law of the combustion performance parameters of the ignition time,heat release rate,mass loss rate,vertical and horizontal burning rate and oxygen index were analyzed.The smoke characteristics of epoxy resin matrix,carbon fiber bidirectional sheet,unidirectional carbon fiber prepreg,carbon fiber sandwich plate and epoxy resin matrix were tested using smoke density chamber and cone calorimeter.The change law of the smoke characteristics parameters of smoke density,total smoke release quantity and CO generation rate and specific extinction area were analyzed.The high-temperature mechanical properties of the three different layers of carbon fiber bidirectional sheet and unidirectional carbon fiber prepreg were tested using microcomputer controlling high-temperature testing machines.The tensile strength and tensile modulus were analyzed under different temperature.The effect of different layers on the high-temperature mechanical properties was studied.The morphology image of carbon fiber bidirectional sheet before and after combustion,and the carbon layer morphology image of epoxy resin matrix and carbon fiber bidirectional sheet after combustion were observed by FESEM.The influence of carbon fiber on pyrolysis and combustion of epoxy resin/carbon fiber composite were analyzed.The results show that the mean ignition time is shortened,the peak and first 300 s average of heat release rate are increased,the peak time was in advanced,the residual percentage after burning is decreased with the increase in radiation heat flux.The lighting time,peak time of heat release rates and CO release time was in advanced due to the low ignition point of the foam core material in carbon fiber sandwich plate.The oxygen index of the samples dropped with increasing temperature.The smoke density of the samples in the flame condition was higher than the smoke density in non-flame condition.The smoke density of unidirectional carbon fiber prepreg was the maximum and the smoke density of carbon fiber bidirectional sheet under was the smallest in the flame and non-flame condition.Carbon fiber had the inhibition effects on the pyrolysis and combustion of composites and the inhibition of the droplet,splashing and a lot of smoke generation in the combustion process.The high-temperature mechanical properties of epoxy resin/carbon fiber composites are related to angle of fiber layer.The more consistent angle of fiber layer with the stress direction there are,the better the mechanical properties of the specimens will be.The high-temperature mechanical properties experience formula of epoxy resin/carbon fiber composites was obtained by data fitting.