Cyclic Loading in PEEK/Graphite Composites: Microscopic Aspects and Fracture Modeling.

In earlier work on the cyclic delamination of graphite/PEEK APC-2 composites, it was determined that the behavior of the material cooled quickly from the melt tested at room temperature and 93C (200F) was significantly different: while the room temperature specimens experienced increasing crack growth with the number of cycles, at elevated temperature the crack growth rate was found to decrease. In this paper, additional data will be presented for a third sample cooled slowly from the melt and tested at elevated temperature. Because of the slow cooling and resulting higher crystallinity and spherulite size, this specimen displayed a greater tendency towards delamination, and as a result it was found that in elevated temperature delamination testing the crack growth became unstable after a shorter period of time.