THE EXPERIMENTAL DETERMINATION OF NATURAL FREQUENCIES OF A BIO-COMPOSITE MATERIAL WITH APPLICATIONS IN THE CAR INTERIOR TRIM, IN ORDER TO EVALUATE ITS MECHANICAL CHARACTERISTICS

The paper presents theoretical and experimental results carried out on a new bio-composite material based on natural fibres with the matrix of polymer or resin modified polypropylene, that can be used for manufacturing certain components of the car interior trim, e.g. door panels. There is presented the way of the experimental determination of the natural frequencies of a rectangular plate, which then will be used in an analytical model for evaluating the equivalent material constants of the plate. Experimental determination of the natural frequencies is accomplished through the method of impact applied using an impulse hammer, equipped with force transducer and with an impact tip, especially chosen depending on the type plate. The natural frequencies so determined were selected, one by one, with the frequency generator, aiming to obtain symmetrical vibration modes. It was noted that the symmetry is disturbed, indicating that the plate material is not homogeneous and isotropic.