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 material. The observation of characteristic quantities provides information on the dynamic fatigue performance. Hysteresis measurements allow measurement of four kinds of quantities: stresses, extensions, stiffnesses and mechanical energies. By means of the stored energy and the energy loss the damping factor is calculated. It is also possible to distinguish between the material behaviour in the tensile loading phase and the compression loading phase. The experimental equipment and procedure for hysteresis measurements are presented here. The application of this test method is demonstrated by two investigations. The first one deals with the dynamic fatigue behaviour of glass fibre reinforced laminates for rotor blades of wind turbines and the second one is the evaluation of a valve spring retainer of carbon fibre reinforced plastic.