Free Vibration Characteristics of Alkali Treated Unidirectional Long Kenaf Fiber Reinforced Epoxy Composites at Various End Conditions

Composite materials are extensively used in many diverse applications such as aircraft strictures, sporting goods, packaging goods, construction and automobile components. Since noise and vibration is common phenomena in the working life, determination of natural frequencies and internal damping of the developed composite materials are in high practical demand, in order to observe the vibration behaviour when they are subjected to periodic exciting forces. The natural frequencies of a system are a function of its mass and elastic properties. Internal damping results from Mechanical energy dissipation within the material due to viscous microscopic and macroscopic processes. Damping capacity and natural frequency are the fundamental properties for designing the components. Damping is one of the significant factors for the fatigue life and impact resistance. Significant improvements have been made towards predicting the vibration behaviour of composite materials for various end conditions. This presents free vibration behaviour of long Kenaf fiber reinforced epoxy composites. The effect of fiber content on the damping and natural frequencies were studied in this investigation. Generally, damping present in the fiber reinforced composite material is more than the metallic material due to its visco-elastic behaviour and fiber matrix interaction. Damping measures rate at which vibration dissipates. In order to improve the mechanical properties, alkali treatment has been done. The vibration test is carried out using National instruments USB 4431 five channel data acquisition module, Endevco 256 small piezoelectric accelerometer and Endevco 2301 impact hammer for different end conditions. The Vibrant technology, ME Scope software is used to convert responses from time domain to frequency domain. Hand lay-up technique is used to prepare the composite plate