The main goal of this project is to examine whether the coatings of current carbon fibres are fully adapted to the thermostable resins (bismaleimides) used for medium-range temperature structural applications.
The fibre/matrix interaction of high modulus (M40) and intermediate modulus (T800) carbon fibres with a bismaleimide resin has been studied by means of three micromechanical techniques involving a single fibre, namely fragmentation, Raman spectoscopy and pull-out. A number of chemical treatments aimed at improving the fibre/matrix stress transfer at elevated temperature were tested. The stress transfer proved to be reduced by the temperature in the same way for any interfacial condition. The limitations to the micromechanical characterization of model composites in temperature are emphasized.
Experimental fibre surface treatment and/or coatings will be compared to the commercial ones by conducting extensive micromechanical (interfacial composites), as well as macromechanical (mechanical testing of unidirectional composites) investigations at temperatures up to 200-250 degreesC.
Finally, the overall thermal-mechanical behaviour of the carbon fibre-reinforced thermostable composites will be modelled, taking into account the combined effects of matrix and interface characteristics, as well as the thermal stress states developed during consolidation of these composites.