ADVANCED TECHNOLOGIES IN DESIGNING, ENGINEERING AND MANUFACTURING RESEARCH PROBLEMS 50 Umit Huner 1 MECHANICAL PROPERTIES OF EPOXY RESIN REINFORCED WITH SILICA/GLASS FIBER Summary: In this work the mechanical properties of polymer composites reinforced with pyrogenic silica and glass fiber are investigated. The epoxy resin used as a Matrix material is MGS LR 160 (Hexion) and the reinforcement particulate materials are silica with particle size (53-63)μm and glass fiber with particle size 6 μm*4.5mm, and having weight fraction of 2.5-20%, 5-20% and 7.5-20% respectively. Specimens of the matrix material and the four types of composite materials were subjected to tensile, bending, and hardness tests. Experimental tests results indicate that the composite materials have significantly higher modulus of elasticity than the matrix material. It was found that the enhancement in modulus of elasticity is directly proportional to the weight fraction of silica. The highest modulus of elasticity is that of the composite with 7.5-20 % silica-glass fiber, which is 182% higher than that of the matrix material. Test results also indicate that material toughness, fracture toughness and hardness of the composite materials are significantly higher than those of the matrix material. The enhancements in these properties are found to be directly proportional to the weight fraction of silica. Keywords: Epoxy, silica, composite, glass fiber. INTRODUCTION In recent years, for the elimination of mechanical, thermal or physical deficiencies in composite materials, to create hybrid material structure has become a solution. The majority of engineering composite materials consist of a thermosetting epoxy matrix reinforced by glass or carbon fibers. Some problems like low toughness, low strain and amount of irregular interface formation, have been attempted to fix with the help of reinforcements conducted in micro- or nano- level. Considering that there are two kinds of reinforcement in the particle modified fiber reinforced composite system, this kind of composite can be categorized as a kind of hybrid composite, which uses more than one reinforcement phase in the system. The hybrid composites are becoming more and more popular due to the mechanical property improvements that were 1 Trakya University, Faculty of Engineering, Department of Mechanical Engineering, 22030 Edirne, Turkey, e-mail: umithuner@trakya.edu.tr