Researches about the Dynamic Behavior of Green Composites Reinforced with Rush and Bulrush

Abstract

The paper presents some researches about the dynamic mechanical properties for some green composites made as follows: the reinforcement is made from rush and bulrush and the matrix is from epoxy resin Resoltech 1050 with its hardener Resoltech 1055. The dynamic parameters were determined from the bars free vibrations. In the first part of the paper, there are presented the mathematical calculus formulas used for the dynamic parameters determination based on the experimental recordings for the free vibrations. The next experimental montage was used: the bars were clamped at one end and were left free at the other end. At the free end, a Bruel&Kjaer accelerometer with 0.04 pC/ms-2 sensitivity was placed in order to record the beams dynamic response. A force was applied at the free end to bend the beams and after bending, the force was cancelled and the beams were left to freely vibrate. The accelerometer was connected to a signal conditioner Nexus and the signal conditioner was connected to a data acquisition system SPIDER 8 made by Hottinger Baldwin Messtec. The acquisition system was connected to a notebook ant the experimental parameters were obtained through CATMAN EASY software. From the free vibrations recording, the following mechanical parameters were determined: the eigenfrequency of the first eigenmode and the damping factors per unit mass. With these values, we have determined some direct calculus formulas for the damping factor per unit mass.