Detection of thermal fatigue in composites by second harmonic Lamb waves

Abstract

Composite materials which are widely used in the aerospace industry, are usually subjected to frequent variation of temperature. Thermal cyclic loading may induce material degradation. Considering the long-term service of aircraft composites and the importance of safety in the aircraft industry, even a little damage that may be accumulative via thermal fatigue is often of great concern. Therefore, there is a demand to develop non-destructive approaches to evaluate thermal fatigue damage in an early stage. Due to the sensitivity of acoustic nonlinearity to micro-damage, the nonlinear ultrasonic technique has been explored as a promising tool for early detection of micro-damage. This paper investigates an experimental scheme for characterizing thermal fatigue damage in composite laminates using second harmonic Lamb waves. The present results show a monotonic increase of acoustic nonlinearity with respect to thermal fatigue cycles. The experimental observation of the correlation between the acoustic nonlinearity and thermal fatigue cycles in carbon/epoxy laminates verifies that nonlinear Lamb waves can be used to assess thermal fatigue damage rendering improved sensitivity over conventional linear feature based non-destructive evaluation techniques. Velocity and attenuation based ultrasonic studies are carried out for comparison with the nonlinear ultrasonic approach and it is found that nonlinear acoustic parameters are more promising indicators of thermal fatigue damage than linear ones.

A micromechanics model for the acoustic nonlinearity parameter in solids with distributed microcracks

“…Since then, a number of researchers, e.g., [10][11][12][13][14], have pursued the use of nonlinear ultrasound as a tool for nondestructive material characterization. In recent years, there has been a resurgence of interest in nonlinear ultrasonic methods [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29].…”

Numerical studies of nonlinear ultrasonic guided waves in uniform waveguides with arbitrary cross sections

“…waves, [16][17][18] evaluation of incipient damages (creep, 19 fatigue [20][21][22] and plasticity 23,24 ) in plate like structures, investigation of the material decay, 25,26 as well as assessment of thermal fatigue damages in isotropic pipes. 27 However, most studies on nonlinear ultrasonic guided waves are limited to simple geometries, such as plates, rods or pipes.…”

Third Harmonic Generation of Shear Horizontal Guided Waves Propagation in Plate-like Structures

“…However, most SH guided wave technologies which based on linear acoustic features, are sensitive to gross defects, but much less sensitive to material micro-damages or degradation [2][3][4][5]. The use of nonlinear ultrasonic wave has been accepted as one of the most promising methods for evaluating material micro-structural changes in early stage [6][7][8].…”