Abstract
Impact brings great threat to the composite structures that are extensively used in an aircraft. Therefore, it is necessary to develop an accurate and reliable impact monitoring method. In this paper, fiber Bragg grating (FBG) sensors are embedded in unidirectional carbon fiber reinforced plastics (CFRPs) during the manufacturing process to monitor the strain that is related to the elastic modulus and the state of resin. After that, an advanced impact identification model is proposed. Support vector regression (SVR) and a back propagation (BP) neural network are combined appropriately in this stacking-based ensemble learning model. Then, the model is trained and tested through hundreds of impacts, and the corresponding strain responses are recorded by the embedded FBG sensors. Finally, the performances of different models are compared, and the influence of the time of arrival (ToA) on the neural network is also explored. The results show that compared with a single neural network, ensemble learning has a better capability in impact identification.
Highlights
Composite structures have been widely used in the aerospace field due to their excellent properties, including high specific stiffness, specific strength, and devisable material properties [1,2,3]
The results show that fiber Bragg grating (FBG) sensors can be embedded inside the composite laminates, and that they have almost no effect on the mechanical properties of the composite structures due to them being small in size and lightweight
The results show that the time of arrival (ToA) is difficult to obtain in the unidirectional carbon fiber reinforced plastics (CFRPs), it can still provide effective information for the ensemble learning model
Summary
Composite structures have been widely used in the aerospace field due to their excellent properties, including high specific stiffness, specific strength, and devisable material properties [1,2,3]. Due to the accurate results and noncontact characteristics of these methods, they are widely used in the field of civil engineering and have made great achievements These methods have not been used to monitor the curing process of composite structures. The transmission of an optical signal will not produce sparks, and so the optical fiber sensor can be used in flammable and explosive environments [18] These characteristics provide the possibility for the real-time monitoring of composite structures in both manufacturing and service. A suitable network of sensors is arranged on the surface of the structure to collect the strain information, which can be used to monitor the impact loads This is a more efficient method than others because the dynamic responses can be measured.
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