Abstract
Low energy impact can induce invisible damage of carbon fiber reinforced polymer (CFRP). The damage can seriously affect the safety of the CFRP structure. Therefore, damage detection is crucial to the CFRP structure. Impact location information is the premise of damage detection. Hence, impact localization is the primary issue. In this paper, an impact localization system, based on the fiber Bragg grating (FBG) sensor network, is proposed for impact detection and localization. For the completed impact signal, the FBG sensor and narrow-band laser demodulation technology are applied. Wavelet packet decomposition is introduced to extract available frequency band signals and attenuate noise. According to the energy of the available frequency band signal, an impact localization model, based on the extreme learning machine (ELM), is established with the faster training speed and less parameters. The above system is verified on the 500 mm × 500 mm × 2 mm CFRP plate. The maximum localization error and the minimum localization error are 30.4 mm and 6.7 mm, respectively. The average localization error is 14.7 mm, and training time is 0.7 s. Compared with the other machine learning methods, the localization system, proposed in this paper, has higher accuracy and faster training speed. This paper provides a practical system for impact localization of the CFRP structure.
Highlights
Carbon fiber reinforced polymer (CFRP) is a very important structural material of the aerospace vehicle
When CFRP is impacted by the low energy impact load, the invisible damages can appear [3, 4]
The impact localization algorithm based on the wavelet packet decomposition and extreme learning machine (ELM) is as follows: (1) According to the monitoring areas, samples are obtained by impact experiments, including the impact signal and coordinate information
Summary
Carbon fiber reinforced polymer (CFRP) is a very important structural material of the aerospace vehicle. Despite the FBG has been utilized for impact detection, only the low frequency strain wave is acquired. The above methods have high localization accuracy, the wave velocity is necessary. It is obvious that localization methods without requiring the wave velocity are necessary for the CFRP structure. Kundu et al [13] used two triangular sensor arrays to locate the impact source in the composite material, and Ciampa et al [14] applied a similar localization principle for the impact localization with six sensors These methods do not require the wave velocity, but the localization accuracy is not high when impact sources are near to the sensor array. FBG sensors and high-speed demodulation are applied to acquire impact signals on the CFRP plate. Comparative experiments are carried on to verify the performance of localization algorithm
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