RESUMEN
Carbon fiber reinforced composites (CFRP) are susceptible to hidden damage from low velocity external impacts during their service life. To ensure the proper monitoring of the state of the composites, it is crucial to predict the location of an impact event. In this paper, fiber Bragg grating (FBG) sensors are affixed to the surface of a carbon fiber composite tube, and an optical sensing interrogator is used to capture the central wavelength shift of the FBG sensors due to low-velocity impacts. A discrete wavelet transform is used for noise reduction in the response signals. Then, the differences in the captured response signals of the FBG sensors at different locations of the impact were analyzed. Moreover, two methods were implemented to predict the location of low-velocity impacts, according to the differences in the captured response signals. The BP neural network-based method utilized three data sets to train the neural network, resulting in an average localization error of 20.68 mm. In contrast, the method based on error outliers selected a specific data set as the reference dataset, achieving an average localization error of 13.98 mm. The comparison of the predicted results shows that the latter approach has a higher predictive accuracy and does not require a significant amount of data.
RESUMEN
Carbon fiber resin-based composite materials are widely employed in the manufacturing of composite shells. During the curing process, the temperature gradients and cure degree gradients make it easy to generate thermal strains in both carbon fibers and resin, with the resin experiencing cure shrinkage strain due to the curing reaction, ultimately leading to residual stresses and strains. In this paper, a three-dimensional thermo-chemo-mechanical coupled curing model of the composite shell was established based on a resin test, and the changes of temperature, curing degree, residual stress, and strain during the solidification of the composite shell were investigated. First, the curing property parameters and elastic modulus of HCM-2184 resin were obtained through a curing dynamic test and a tensile test. Then, considering the heat release and shrinkage reaction of solidification, a coupled thermo-chemo-mechanical curing model was developed with the CHILE (α) elastic model, and the curing process of the composite shell was simulated numerically. The results show that the resin used in the test belongs to the autocatalytic reaction. For thin composite shells, the heat accumulation inside the shell during curing is not obvious. During the curing process, the curing shrinkage behavior of the resin is an important factor for the generation of residual stress and residual strain.