Abstract
Carbon fiber reinforced polymer (CFRP) laminates, as unique multifunctional materials, are widely applied in various aircraft, such as airliners, fighter planes, and space shuttles. To ensure aircraft safety during the production and application of CFRP laminates, it is necessary to improve the accuracy of nonlinear Lamb wave nondestructive testing to assess the damage in CFRP laminates caused by impact, high temperature, friction, corrosion, etc. In this study, the accuracy of nonlinear ultrasonic nondestructive testing was found to highly depend on the cycle number, output level and gain of the nonlinear ultrasonic detection system. Based on a single-factor experiment that considered the cycle number, output level, and gain of the amplifier as independent variables, a regression analysis was carried out on the fundamental wave amplitude value (A1) and second harmonic amplitude value (A2). Two response surface surrogate models were established to improve the accuracy of nonlinear Lamb wave nondestructive testing and to optimize the detection system parameters. The response surface models were verified via an analysis of variance (ANOVA), significance tests and an error statistical analysis. The results revealed the significant influence of these three factors on A1 and A2. Optimization of the response surface was achieved at eight cycles, an output level of 42 and a gain of 32 dB. Moreover, the nonlinear ultrasonic detection system achieved good operational stability, high accuracy and reliability under the above optimal parameter conditions. This approach provides scientific guidance for the accurate assessment of CFRP laminate damage.
Highlights
Carbon fiber reinforced polymer (CFRP) laminates are extensively applied in the electronics, military, and aerospace fields due to their excellent mechanical properties [1,2,3,4]
Regression models that describe nonlinear ultrasonic amplitudes A1 and A2 and the relationship among the cycle number, output level, and gain were obtained via central composite design (CCD)
The reliability of these response surface models was verified through analysis of variance (ANOVA), error statistical analysis and normal probability distribution determination of the residuals
Summary
Carbon fiber reinforced polymer (CFRP) laminates are extensively applied in the electronics, military, and aerospace fields due to their excellent mechanical properties [1,2,3,4]. In this study, based on different parameter settings in the RAM-5000 SNAP nonlinear ultrasonic detection system, according to the CCD design principle of the RSM, the experimental conditions of the nonlinear ultrasonic nondestructive testing amplitudes A1 and A2 were optimized. The optimal experimental conditions were explored by RSM, and a theoretical basis for further studies on nonlinear ultrasonic detection was provided This simple and reliable evaluation method of material damage may greatly improve the accuracy of online, dynamic, and real-time aircraft structural health monitoring (SHM) systems of aircraft composites during operation, and achieve a qualitative leap in safety monitoring and the performance of engineering structures. To overcome the effect of random noise generation, the relative error of the repeated measurement is set below 1.5%
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