Study On Fireproof Characteristics And Compliance Demonstration For Airworthiness Of Typical Aircraft Composites

Composites has remarkable advantages such as high specific strength and specific modulus, strong design ability, good fatigue strength and corrosion-resistant, easy integrated forming etc. which shows a higher comprehensive performance than traditional metal structure materials. Epoxy resin/carbon fiber composites are widely applied to the field of aviation and aerospace at present. Since its flammability, it will release a great amount of heat and smoke with the mechanics capability degradation when exposed to the conditions of high temperature or fire, which will produce the danger of destruction to aircraft. Besides that,the requirements of the fireproof characteristics for composites in the current domestic airworthiness standards are much less than traditional metal structure materials. So, it is necessary and important to study on the fireproof characteristics of aircraft composite.The researches object of this thesis was epoxy resin/carbon fiber composites, which have widely used in light aircraft, and focuses on the fireproof characteristics of three typical epoxy resin/carbon fiber composites including uni-directional carbon fiber prepreg, carbon fiber bidirectional sheet and carbon fiber sandwich plate. The results indicate that the ignition positions have a great influence on flame-propagating velocity, and it has a faster speed when ignited on the bottom of the material. Foam core material is easy to form carbon layer in the process of heating, and the formation of the carbon layer have important influence on the fire characteristics, which will reduce flame spread rates, increase limiting oxygen concentration.But the foam core material decomposed at lower temperatures, which lead to ignition time,time of the peak HRR, pyrolysis and heat release all in advance. Weaving method have little influence on combustion performance and thermal stability of carbon fiber composite materials with the same epoxy system. Combing the current data of the integrated thermal gravimetric analyzer and the thermal decomposition kinetic parameters, carbon fiber bidirectional sheet have a better thermal stability than uni-directional carbon fiber prepreg in the temperature range of the experiments.Fire risk of three typical epoxy resin/carbon fiber composites was comprehensiveevaluated combined with the test dates. Evaluation results show that the fire risk of uni-directional carbon fiber prepreg is close to carbon fiber bidirectional sheet, and the fire risk of carbon fiber sandwich plate is relatively large. finally, through the analysis of the fire risk characteristic of light aircraft and civilian aircraft, a framework of authentication scheme for light aircraft airworthiness is established, such as fire spread test, heat release rate test, the mechanism test of the pyrolysis and combustion, smoke and its toxicity test, oxygen index test etc.