THERMOPLASTIC SIZING OF CARBON-FIBERS IN HIGH-TEMPERATURE POLYIMIDE COMPOSITES

Thermoplastic sizing of various carbon fibres has been evaluated as a means of controlling the microcracking resistance, transflexural stren gth (TFS), and thermo-oxidative stability (TOS) of PMR-15 matrix compo sites. Four different fibre/thermoplastic size combinations were selec ted for this study, based on their higher TOS than appropriate control s. Data are presented for the transverse microcrack (TVM) density/inch , and the subsequent delamination of [0,90](4s), laminates induced by thermal cycling (-196 to 350 degrees C for 20 cycles). Results for com posite TFS, conditioned TFS (after heating in air at 350 degrees C), a nd TOS (350 degrees C and 316 degrees C) are also reported. One fibre/ thermoplastic size combination gave both good microcracking resistance , and significantly improved TOS, in composite when compared with curr ent commercially-available material.