Dynamic mechanical analysis of banana fiber reinforced polyester composites

The dynamic mechanical analysis of banana fiber reinforced polyester composites was carried out with special reference to the effect of fiber loading, frequency and temperature. The intrinsic properties of the components, morphology of the system and the nature of interface between the phases determine the dynamic mechanical properties of the composite. At lower temperatures (in the glassy region), the E′ values are maximum for the neat polyester whereas at temperatures above Tg, the E′ values are found to be maximum for composites with 40% fiber loading, indicating that the incorporation of banana fiber in polyester matrix induces reinforcing effects appreciably at higher temperatures. The loss modulus and damping peaks were found to be lowered by the incorporation of fiber. The height of the damping peaks depended on the fiber content. When higher fiber content of 40% was used, an additional peak in the tan δ curve, pointing to micro mechanical transitions due to the immobilized polymer layer was evident. The glass transition temperature associated with the damping peak was lowered up to a fiber content of 30%. The Tg values were increased with higher fiber content. Cole–Cole analysis was made to understand the phase behavior of the composite samples. A master curve was constructed based on time–temperature super position principle, which allows the prediction of long-term effects. Apparent activation energy of the relaxation process of the composites was also analyzed. The value was found to be maximum for composites with 40% fiber content.