Study of epoxy and epoxy-cyanate networks thermal degradation to predict materials lifetime in use conditions

Composite materials are used more and more for aeronautical applications an d they have to be as thermally stable as possible. The thermostability of c arbon-fiber/epoxy-cyanate composites elaborated with an autoadhesive and au toextinguish prepreg were tested, Dynamical and isothermal aging tests were carried out to evaluate the composite thermal stability. Thermal degradati on products were identified by chromatography/mass spectrometry analysis an d the results obtained were compared with data known on the material networ k structure. The physicochemical network structure evolutions and the therm al aging data are correlated with the interlaminar shear strength (ILSS) me chanical results. For epoxy-cyanate composites, cracking appears after a lo nger time of aging than for epoxy composites. This new epoxy-cyanate materi al isothermal stability seems to be good and particularly good if it was po stcured after processing. The comparison of chemical, mechanical, and crack formation results obtained by accelerated aging tests allowed us to determ ine models to predict long-term behavior. (C) 2000 John Wiley & Sons, Inc.