Characterisation of delamination failure in composite wind turbine blade using refined delamination factor

Abstract

Wind turbine is now being used as a generic term for machines with rotating blades that convert the kinetic energy of wind into useful power. Utilisation of renewable wind energy in India increases in many folds from the last decade of 20th century. The wind turbine blades are fabricated using glass fibre reinforced composite materials. Wind turbine blades are complex section, since it includes the aerofoil section of varying thickness from leading to trailing edge, varying chord length from hub section to tip section, inclusion of blade twist angle and pitch angle along its length. In order to improve the strength of the blades under varying loading conditions, spars are embedded in it. The spars are fastened with the composite shells of the blades using bolted connections. In order to affect this fastening, holes of appropriate size were drilled in the composite laminates. Drilling is probably the machining process most widely applied to composite materials; nevertheless, the damage induced by this operation may reduce drastically the component performance. In order to establish the damage level, delamination is measured quantitatively using digital means. A comparison between the conventional (FD) and adjusted (FDA) delamination factor is presented. In order to quantify the delamination effectively, refined delamination factor (FDR) is proposed.