The present work relates to the processing of dense alumina-based composites, their microstructural characterization and study of mechanical properties. Alumina ceramic material and alumina-based composites with m-Zirconia and Ceria addition are sintered at 1600°C, 1650°C and 1700°C temperatures via conventional sintering. Solid-state diffusion during sintering led to volume diffusion in alumina, and volume and grain boundary diffusion in alumina composite. In the present sintering conditions alumina is found to be the least dense as improper solid-state diffusion resulted in porosity, whereas alumina–zirconia composite achieved the highest density of 97%. Scanning electron microscope (SEM) micrograph shows homogeneous distribution of fine zirconia particles inside the alumina matrix, filling the voids of the alumina skeletal structure. Zirconia connects to alumina particles, restricting its abnormal grain growth. It results in strong bonding and grain refinement. Alumina–zirconia composite exhibits the highest hardness and fracture toughness of 14.37 GPa and 4.6 MPa · m^1/2 at 1700°C. Alumina suppresses the transformation of m-t zirconia, resulting in high toughness of alumina composites. Alumina–zirconia–ceria composite revealed the presence of porosity, which led to less densification and low mechanical properties.

Advanced mechanical and wear properties and applications of composites with bases of light weight metals have led to the need of aluminium (Al) metal matrix composites (MMCs). In today’s time aluminium (Al) metal matrix composites (MMCs) are considered the most potential material for structural and functional applications. Composite materials with aluminium matrices are used in defence, aerospace, automotive and aviation, thermal management areas. Beneficial properties with reduced prices have enlarged their applications. To obtain desired physical and mechanical properties like high hardness, high strength, high stiffness, high wear, abrasion and corrosion resistance Al is reinforced with different metallic, non-metallic and ceramic elements. Al MMCs are used to make piston, connecting rod, engine cylinders, disc and drum brakes where wear has a great role in the functioning of these components as excessive wear of the mating components sometimes leads to catastrophic failures. Improvement of mechanical, especially tribological properties of hybrid composites were provided by the use of certain reinforce materials such as SiC, Al2O3 and graphite. Hence the present chapter presents a review on aluminium metal matrix composites (MMCs) reinforced with different particulate, whisker, fibres reinforcements highlighting their effect on physical, mechanical and wear behaviour of Al MMCs.

In engineering applications, fracture toughness is an essential requirement that determines the life of a material. Epoxy polymers are widely used in fibre-reinforced composite materials. Due to their structural efficiency and durability, the use of adhesive and composite materials based on epoxy polymers is widespread in aerospace and automobile industries. In this paper fracture toughness of hybrid epoxy polymer composite with addition of nano/micro figures of silica, rubber and carbon nano tubes (CNTs) is evaluated. It is observed that silica addition promoted nano toughening effect with plastically deformation capability in epoxies. Rubber and multi walled CNTs increased the toughness with negligible reduction in stiffness in epoxies. Future research emphasis can be laid on crucial understanding of stress transfer mechanisms and interfacial bond strength between nano particles – epoxy system and on nanofillers modified epoxies as matrices or interleafs for carbon or glass fiber composites to increase the interlaminar delamination toughness.