"PROCESSING, MICROSTRUCTURE AND ELECTRICAL PROPERTIES OF CARBON FIBRE REINFORCED THERMOPLASTICS"
Ricardo H. Cruz-Estrada
16th OCTOBER, 1995 - 16th FEBRUARY, 1996
Technological interest in composites with enhanced electrical conductivity has grown because of their applications in electromagnetic shielding for electronic devices and their capability in electrostatic charge elimination in electronic components. Carbon fibre composites based on engineering polymers with high melting points has been widely used specially in aircraft industry. Experiments have focused mainly on the mechanical properties of the composites, although electrical properties of carbon fibre composites have also been reported. These materials are specially attractive because composites with fibre fillers exhibit a greater degree of interconnection at lower concentration than systems with spherical shape fillers.
For the purposes of the present training course, polypropylene-carbon fibre composite materials were manufactured by extrusion and injection moulding using different compositions. The microstructure was analysed in directions perpendicular and parallel to the injection flow direction by light microscopy. DC conductivity measurements and tensile tests were carried out in directions perpendicular, parallel and at 45o to the injection flow direction. Experimental results show, on the one hand, that the carbon fibre orientation in the composite material is closely related with the material flow direction into the injection mould during the processing. On the other hand, it is also shown that the electrical conduction degree and the mechanical properties are intimately related with the composition of carbon fibres and the injection flow direction.
The main object of this work was to receive technical training concerning manufacturing techniques of thermoplastics polymer-carbon fiber composite materials with electrical applications. Also, another important objective was to acquire experience with respect to the most appropriated methods to determine the electrical and mechanical properties and to characterise the microstructure of this kind of materials.