Life prediction methodology for GFRP laminates under spectrum loading

A complete life prediction methodology for glass fiber reinforced plastic laminates accounting for plane stress states and spectrum loading is presented in this paper. Fatigue strength allowables in the laminate symmetry axes are derived by direct characterization for a number of different constant amplitude loading cases. Experimental results from tests inducing plane stress states, conducted using two different loading spectra of variable amplitude, were used to validate the entire methodology. The first loading spectrum is a modified version of the well known in wind turbine rotor blade research activities, WISPERX, while the second one is derived through aeroelastic simulations of a realistic loading case for a small glass fiber reinforced polyester rotor blade. The effectiveness of the methodology is investigated and correlated to several parameters that affect life prediction, such as, type of loading, baseline data, damage accumulation rule, etc.