FABRICATION AND CHARACTERIZATION OF FUNCTIONALLY GRADED MATERIALS: STUDY OF MICROSTRUCTURE IN CENTRIFUGAL COMPACTION AND HOT PRESSING PROCESSES

Abstract

In recent times, remarkable progress in science and technology has prompted scientists to create a new category CCP of structural materials with enhanced characteristics. Functionally graded materials (FGMs) are a new type of composite materials made up of two or more components that are continuously varied in their distribution. The idea of FGMs can be utilized to exploit the advantageous properties of each constituent phase and adjust the distribution of material properties to achieve the desired response to specific mechanical and thermal loads or to modify natural frequencies in a desired manner. To fully utilize the exceptional properties of FGMs in the development of new products, it is essential to conduct fundamental studies on the mechanics of these materials, as well as research on their processing. The first study investigates the application of centrifugal force for the compaction of metal powders. Aluminium alloy powder with a particle size less than 100 µm and polymer binder were mixed and compacted in the centrifugal machine with varying degrees of centripetal acceleration. SEM micrographs of the green bodies' microstructure showed significant packing densities and an increase in median particle size at sites further from the centrifuge's centre of rotation. The segregation phenomena was not observed at 700 G, but clear particle segregation was found at higher centrifugal forces. This investigation focuses on the development of topologically complex FGM by controlling interfacial microstructure through CCP-based compaction. The second study examines poly(ether-ether-ketone) (PEEK) and graphite-based high-performance laminate composite materials. The structural, thermal, and mechanical characteristics of the composites, which were created utilising the hot press technique at temperatures below 310°C, were carefully examined and described. SEM images indicated a strong interfacial contact between PEEK and graphite. This research focuses on the design of PEEK/graphite FGM with topologically complex multi-scale compositions and revealed improved mechanical and thermal properties due to the synergistic effect of incorporation of two dissimilar materials under high temperature and joining load. Overall, this dissertation provides insights into the design and fabrication of materials with multi-scale topologies. The research focuses on understanding the interfacial behaviour of materials at various scales and developing fabrication methods to produce materials with desired properties.