EVALUATION OF COMPOSITES UNDER DYNAMIC LOAD

During the dynamic fatigue test it is desirable not only to determine the fatigue strength, but also to characterize the damage in the mater ial. The observation of characteristic quantities provides information on the dynamic fatigue performance. Hysteresis measurements allow mea surement of four kinds of quantities: stresses, extensions, stiffnesse s and mechanical energies. By means of the stored energy and the energ y loss the damping factor is calculated. It is also possible to distin guish between the material behaviour in the tensile loading phase and the compression loading phase. The experimental equipment and procedur e for hysteresis measurements are presented here. The application of t his test method is demonstrated by two investigations. The first one d eals with the dynamic fatigue behaviour of glass fibre reinforced lami nates for rotor blades of wind turbines and the second one is the eval uation of a valve spring retainer of carbon fibre reinforced plastic.