Ply-Resolved Quantification of Thermal Degradation in Carbon Fibre-reinforced Polymers

Abstract

This study focuses on thermal degradation of carbon fibre-reinforced polymers depending on the specimen depth. For this purpose, the commercial composite HexPly ® 8552/IM7 was thermally irradiated from one side with an infrared lamp at constant heat flux of 50 W/cm 2 under varying exposure time. Subsequently, a defined number of plies was removed to prepare micro samples from different depths of the bulk material. Non-destructive and destructive testing methods were used to characterize the thermal degradation mechanism and mechanical properties of these specimens. The results showed that during thermal loading temperature and consequently damage gradients manifest along the material cross-section. Thereby, the damage distribution could be divided into the regions r I with matrix depletion, r II with and r III without structural damage such as delaminations, cracks and pores. By means of ply-resolved investigations, the influence of these regions and corresponding decomposition processes on the mechanical properties could be determined. As a result, a simple damage model was introduced to calculate the residual strength from the initial strength, region sizes and sensitivity factors representing the effect of thermo-induced damage on strength types.