Service Damage Assessment of Composite Rotorcraft Blades: A Methodology to Predict Internal Damage from Surface Dents

The aim of the present work is to understand and quantify the effect of service damage on structural integrity of rotorcraft composite blades. Such damage, observed in service and transportation conditions, may generate invisible internal damage and fracture processes that may control repair-related decisions and/or residual blade life. Such internal damages can be associated with external easily measurable signs such as dents on the blade surfaces. Thus, the objective of this work is to a) propose an approach to correlate external visible dents in the blade pocket region with internal invisible damage in the core; b) develop its efficient computational implementation; and c) demonstrate it on a wide range of service-induced damages on a representative blade. A hybrid computational-experimental methodology is developed to achieve these objectives. Systematic parametric studies are performed to understand major trends and transform them into relatively simple master-curves convenient for engineering practice. Also, an experimental approach is developed to quantify the time-dependent nature of the core deformation and its effect on the evolution of surface dent size at long times after the impact event. Generated results and the developed methodology can provide opportunities for significant cost saving through reduction of over-conservativeness in the traditional repair trigger limits.