Shin E.

This paper presents the dynamic characterization of a flexible matrix composite (FMC) driveshaft. A primary objective is to experimentally validate the equivalent complex modulus approach in analytic modeling of a FMC shaft. A testrig is developed that consists of a FMC shaft, a support beam and bearings, a driving motor and a shaker. The experimental characterization of the FMC shaft is performed by applying two types of external loadings. First, the shaker excitation is applied vertically to the shaft through the support beam with the frequency sweep up to 130 Hz. Second, imbalance loading is imposed while spinning up the shaft continuously near the 1st resonance. Optical probes are employed to measure the shaft responses in the vertical and horizontal directions. In addition, three types of sensors are used for monitoring the input excitation: a force sensor for the shaker excitation, accelerometers for the support beam motion and a tachometer for the spin-up speed. Finally, frequency response functions (FRFs) and transient responses are obtained. Results show that the measured FRFs around vertical shaft modes are observed in a fairly good correlation with the predicted. Although the measured FRF peaks corresponding to horizontal modes are not well matched with the analytical results, the difference is mainly caused by coupling with the support beam. Consequently, the shaft modeling based on equivalent modulus approach is valid enough to estimate the shaft dynamic behaviors. This is further validated by spin-up results, where a good agreement in the rate of response increase is exhibited between the measured and the predicted.