Mechanical Properties of Carbon/Polypropylene Fiber Reinforced Rubber-Modified Epoxy System

Abstract

Epoxies as a thermoset polymer have gained a considerable attention in structural, electrical, and marine applications. To widen their usage and overcome their brittleness, many polymers were blended with it. The addition of Polysulfide rubber helps in increasing the impact resistance of Epoxy, while in the other hand; it reduces strength , modulus, hardness and creep resistance. That leads to the need for another material to compensate the reduction in these properties.

Carbon, polypropylene as an inorganic and polymeric short fibers with their exceptional and different mechanical properties will compensate many drawbacks of polysulfide addition in enhancing mechanical properties. The composite material with Epoxy-Polysulfide matrix properties were evaluated by conducting the mechanical tests which include compression test, hardness test, impact resistance test. The fracture surface of composite impact specimens was observed by Scanning Electron Microscopy SEM on all designed experimental samples.

Elongation and impact strength of epoxy- polysulfide blend were found to increase with increasing rubber content while compressive strength and modulus decrease. The influence of fiber adding on the mechanical properties of the composite was studied , the mechanical properties of the blend matrix were found to be better than those of the pure epoxy. The morphology of the fractured surfaces showed significant signs of plastic deformation such as shear bands, high deformation, and cavitations due to rubber addition, and this correlates well with mechanical properties which resulted in an increase in toughness of the composites when rubber content was increased. The results of this investigation clearly show the possibility of balancing strength and toughness of the material when adding rubber, fiber to epoxy.

Results of compression test showed that the compressive strength decreases as Polysulfide percentage (PS) increase. While the carbon fiber addition helped in balance or overcomes the original compressive strength reduction up to 30 vol.%. of fiber. The results confirmed that the best modification is the addition of 6% polysulfide considering compressive strength, Impact and hardness. While 20% carbon fiber and 30% Polypropylene fiber gives the optimum mechanical properties in compression and Impact, respectively, for the composite samples.

Keywords: Epoxy resin, Liquid rubber, Mechanical properties.