Fatigue strength assessment of a short fiber composite based on the specific heat dissipation

An energy-based approach is proposed and validated to analyse the fatigue strength of plain and notched specimens made of a short fiber-reinforced plastic weakened by rounded notches. A previous theoretical model based on an energy balance is presented, where the different forms of energy exchanged in a fatigue test are involved. Among these, the energy dissipated as heat by a unit volume of material per cycle is assumed as fatigue damage indicator. An experimental technique which enables the estimation of the proposed energy parameter is presented and applied to analyse the fatigue behaviour of the plain and notched specimens. Differently from the nominal stress or the elastic peak stress, the adopted energy parameter is able to correlate the fatigue strength of the considered specimens independently of the geometry. The limitations of applicability of the presented approach when reducing the notch tip radius are also discussed.