Computation of energy release rates for composite beam through cross-sectional analysis and virtual crack closure technique

Abstract

This study theoretically describes VCCT (virtual crack closure technique) as well as the dimensional reduction and recovery relations of cross-sectional blades, composed of composite materials, like a wind turbine blade that has a high aspect ratio and initial twist. Besides, to verify the efficiency and accuracy of dimensional reduction and recovery analysis of such a wind turbine blade, this study compared the recovery analysis results of a dimensionally reduced 1-D beam with the analysis results of a 3-D finite element model. Then, this study extracted nodal loads and nodal displacements of cracks, which are required for VCCT, using the recovery analysis results, and then conducted VCCT using the relations between nodal loads and displacements of extracted cracks, further suggesting a process of calculating ERR (Energy Release Rates) through the results of VCCT. As a numerical model and a turbine blade model, having initial cracks on the rectangular cross-section, are needed when ERR is calculated with VCCT applied to the finite element model and the dimensional reduction model, this study applied dimensional reduction & recovery technique and VCCT to these models and verified the efficiency and accuracy by comparing recovery analysis results and ERR.