Research On Acoustic Emission Detection Signal Analysis Of 3D Braided Composites Based On HHT

Three-dimensional braided composites do not require suturing and machining,with good overall performance indicators such as high specific strength,specific modulus,high damage tolerance and fracture toughness,impact resistance,delamination,cracking and fatigue resistance,And with the third phase composite form excellent mechanical properties of the components.For nearly half a century,braided structural composites have been widely used in aerospace,aviation,transportation.construction,military,medical and sports fields.Although the strength of composites is very good,the three-dimensional braided composites as carrier materials are often exposed to various conditions during use or manufacturing.such as impact,impact load and extreme changes of temperature,etc.,and different types of Defects or injuries(such as cracks,debonding or delamination.etc.).Therefore,it is necessary to inspect the three-dimensional braided composites under working condition.As an important method in acoustic detection,acoustic emission detection can obtain the internal damage signal of the composite material under load,and establish a direct correspondence between the collected signal and the development and change process of the internal damage of the material.Through a series of signal analysis techniques After the acoustic emission source signal is denoised and the sound source waveform is identified,the location of the damage source is finally obtained.Acoustic emission detection technology has become one of the important methods for non-destructive testing of three-dimensional braided composites.This paper mainly introduces three typical methods of time-frequency analysis,which are Fourier Transform,Wavelet Transform and Hilbert-Huang Transform.The basic concepts and basic properties of them are introduced briefly.Combining with three types of typical signals,The above methods were compared.Combined with experimental simulation and three-dimensional braided composite tensile test,Hilbert-Huang obtained the decomposition components of different scales by directly constructing the basis function of the signal by local features of the signal,especially after introducing the resolution idea Possible modal aliasing in signal decomposition.This method is very suitable for studying the time-frequency characteristics of acoustic emission signals,revealing the time-frequency characteristics unique to the signals,which has good local adaptability and intuitiveness of the analysis results,and is larger in resolution than the traditional time-frequency analysis methods improvement.Through the research,find the suitable time-frequency analysis technology for three-dimensional braided composite acoustic emission detection signal.