Characterization of carbon fiber reinforced high density polyethylene

Nowadays, using of fiber-reinforced polymer in matrix composites is becoming very common. The discriminative properties of carbon fiber has been constraining fiberglass ''the most used material in reinforcing'' to leave its place forever. Its high tensile strength and tensile modulus make it very distictive comparatively to the other fiber materials. Regarding to matrix composites, it seems that shelf life and recyclable properties have been highlighting the worth of using thermoplastic matrix instead of the very common thermoset matrix. In this study, high density polyethylene ''the most common thermoplastic material'' has been chosen as a matrix material, chopped carbon fiber as a reinforcing material. The chosen high density polyethylene matrix has been reinforced by using different percentages by weight of carbon fiber. In this thesis, investigation of thermal and mechanical properties of carbon fiber-reinforced high-density polyethylene was aimed. With this purpose, the composites were by handling the materials with extrusion compounding and injection molding techniques. Impact test, hardness test, and tensile test were done for the mechanical characterization of the prepared composite samples. Differential scanning calorimetery (DSC) was used to determine the thermal properties of the composite samples, and scanning electron microscopy (SEM) for surfaces characterization. Polymeric matrix was reinforced by handling with four by weight different percentages of carbon fiber (5%,10%,15%, and 20%). In addition, comparatively, polymeric matrix was also reinforced by handling with two by weight different percentages of fiberglass (10% and 20%). It was observed that hardness, impact strength and tensile modulus values were increased simultaneously by increasing the amount of carbon fiber, unlike elongation which showed the opposite reaction. Increasing in weight of carbon fiber doesn't make a salient change on DSC's results. However, SEM showed that adhesion between the fibers and the matrix is not very good. Tensile tests' results have observed that tensile strength hasn't been effected as much as tensile modulus did and that because, tensile modulus is dependent on carbon fiber volume fraction, while tensile strength is dependent on mean fiber's length. Studies show that the mean length of fiber becomes shorter with fiber reinforcing, studies also observed that mean length of fibers is being shortened much more when we use carbon fiber in reinforcing than when we use fiberglass. Key Words: High density polyethylene, carbon fiber, characterization, composite