In recent years, composite materials have garnered attention, as various combinations of reinforcements can be incorporated to create lightweight materials with diverse properties. Composite materials can be tailored for particular applications and made suitable for adverse atmospheric conditions. A new, challenging research area involves the formulation of innovative materials with less weight, higher stiffness, lower costs, and higher biocompatibility. Examples of applications for such materials include electric vehicles, defense vehicles, aircraft parts and industrial machine structures. The incorporation of natural and inorganic filler to Kevlar epoxy composite shows improved behavioral properties compared to either natural or inorganic filler alone. These properties include tensile, flexural and interlaminar shear strength as well as thermal performance. This book aims to describe the advantages of using bi-filler reinforcement over single filler reinforcement to enable the development of innovative composite materials with tunable properties.