Study On Mechanical Behavior And Acoustic Emission Response Characteristics Of The Delamination Damage Evaluation For Wind Turbine Blades

In recent years, wind power has been paid more and more attention in the development and utilization of the clean energy in our country. In the actual working conditions, delamination and other structure defects affected in the process of manufacturing will accumulate and result in the damage and bulk failure of wind turbine blades. Acoustic emission(AE) is sensitive to dynamic defects, which can be used to monitor the damage and failure progress of the composite materials. Application of AE techniques for wind turbine blades in the early damage discovery and prediction and defect location has become increasingly mature. But few studies concern on the delamination damage evolution characteristics and AE response characteristics of composites for wind turbine blades. The investigation of delamination damage evolution process applying AE technology has great significance to ensure the wind turbine blades to long-term stable operation.This study improved the existing vacuum infusion process, and obtained the circulatory system of vacuum perfusion resin reflux, which has good wettability and recyclability. In order to study the damage evolution of interlaminar interface [0/0], [0/45] and [+45/-45] in composites material for wind turbine blades, mode I and mode II delamination growth experiments of the composites have been conducted by means of AE technique. The delamination damage evolution and AE response characteristics were obtained through the analysis of mechanical property, interface microstructure characteristics, AE characteristic parameters and wavelet. And provided a reference for health monitoring of composite structures.The mode I delamination damage evaluation of composite material for wind turbine blades can be divided into initial stage, evolutionary stage and failure stage. The AE amplitude signal of [0/45] and [+45/-45] composite material specimens were much more than that of [0/0] layered composite specimens at the evolutionary stage and failure stage. And AE relative energy peak value was higher than that of [0/0] layered composite specimens. The mode II delamination damage evaluation of composite material for wind turbine blades can be divided into two basic stages, the micro damage accumulation around crack tip region and delamination unstable extension. Unstable crack extension of [0/0] layered composite specimens is connected with high amplitude, long duration time AE signal. The micro damage degree of [0/45] and [+45/-45] composite specimens is more serious at the crack tip region.In this paper, wavelet analysis of AE signal for mode I and II composite material specimens has been discussed. The main method is to select the suitable wavelet, calculate the energy spectrum coefficient of each layer and reconstruct the maximum energy spectrum coefficient. Spectrum analysis method has been conducted to analyze the signal processing. The results show that two failure modes signals are burst-type signal, and the maximum spectrum coefficient in the D4 layer. Different interlaminar interface and delamination mode, the failure mechanism of composite materials are different.