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Fracture behavior of carbon fiber reinforced polymer composites: An optical study of loading rate effects
摘要： Crack initiation and growth in single-edge notched unidirectional T800s/3900-2 CFRP laminates are studied under stress wave and quasi-static loading conditions. An optical technique called reflection-mode Digital Gradient Sensing is also extended to study fracture mechanics of CFRP by using it in conjunction with ultrahigh-speed photography to perform full-field measurement of crack-tip deformations in the pre- and post-crack initiation regimes. DGS is capable of measuring two orthogonal surface slopes in the crack-tip vicinity as angular deflection of light rays. A method for extracting crack-tip parameters - the instantaneous crack speed and stress intensity factor (SIFs) histories - associated with the stationary and propagating cracks using measured surface slopes is presented. The effect of fiber orientation in the range 0°-60° relative to the initial notch and two loading rates are investigated. Nominally mode-I fracture occurs when the fiber orientation is 0° whereas mixed-mode fractures ensue in others. Besides crack initiation occurrence at higher loads as fiber orientation increases, the SIF histories imply strong fiber bridging at low fiber orientations under quasi-static conditions. Furthermore, this CFRP shows significant loading rate dependence during crack growth. Unlike stress wave loading conditions, an increasing crack growth resistance immediately after crack initiation is seen under quasi-static conditions.
关键词： Carbon fiber reinforced plastics,Loading rate effects,Crack growth behavior,Dynamic fracture,Digital Gradient Sensing
更新于2025-09-23 15:23:52
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Damage degree prediction method of CFRP structure based on fiber Bragg grating and epsilon-support vector regression
摘要： The assessment of structural damage is of great significance for ensuring the service safety of carbon fiber reinforced plastics (CFRP) structures. In this paper, the damage degree prediction method of CFRP structure based on fiber Bragg grating and epsilon-support vector regression was studied. The structural dynamic response signals were detected by fiber Bragg grating sensors. Then, the Fourier transform was used to extract the dynamic characteristics of the structure as the damage feature, and the damage feature dimensionality was reduced by using the RReliefF algorithm. On this basis, the damage degree prediction model of CFRP structure based on epsilon-support vector regression was established. Finally, the method proposed in this paper was experimentally verified. The results showed that the epsilon-support vector regression model can accurately predict the damage degree of unknown samples, and the absolute relative error of 27 experiments was less than 10% for 30 testing experiments. This paper provided a feasible method for predicting the damage degree of CFRP structures.
关键词： Frequency response,Carbon fiber reinforced plastics,Epsilon-support vector regression,RReliefF,Damage degree prediction
更新于2025-09-23 15:23:52
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Minimal Magnetic Dipole Moment for the Solar Cell Array Using GaInP/GaAs/Ge Cells
摘要： The only ambient power source in space is solar energy, which is harvested by photovoltaic conversion with solar cells. Since about 20 years ago, silicon solar cells have been used extensively as the primary power devices in space. However, in recent years, GaInP/GaAs/Ge solar cells with triple junction technology, have been widely used as power-generation devices for space applications. Not only do the GaInP/GaAs/Ge solar cells have better conversion efficiency compared to Si solar cells, but it is also possible to supply the required electric power using a smaller number of solar cells. While there are advantages when using the GaInP/GaAs/Ge solar cells, methods for design of systems of strings should be established for minimizing their magnetic dipole moment. This is because the voltage and current are three times greater than with Si solar cells, and this must be considered. By electromagnetic theory, loop current of a string consisting of cells in series occurs when flowing through it. That magnetic dipole moment can affect attitude control when using magnetic torque bars in orbit, and spacecraft systems require no more than 0.25 Am2 of magnetic dipole moment for optimal attitude control. Therefore, we designed a single string of GaInP/GaAs/Ge solar cells and tested its current capacity to see and minimize the magnetic dipole moment. Finally, we proposed an optimal string design methodology by a test coupon solar cell array using GaInP/GaAs/Ge solar cells by simulation and implemented it on a substrate of carbon fiber reinforced plastic material to see how well the prototype worked or did not work. In future, the string design methodology could be extended to a larger solar cell array by using this coupon design methodology to minimize the magnetic dipole moment.
关键词： Carbon fiber reinforced plastics,GaInP/GaAs/Ge,Solar cell,String,Magnetic dipole moment
更新于2025-09-19 17:13:59
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Evaluation of internal defects generated in machine milled carbon fiber reinforced plastic using X-ray computed tomography
摘要： In this study, X-ray computed tomography (X-ray CT) was used to investigate internal defects generated on machine milled carbon fiber reinforced plastics (CFRP). Internal defects such as cracks, fractures, and deformation of the carbon fibers, which are invisible from the surface, were observed using the X-ray CT method. Defects were generated based on the machining method and direction of the fibers. A large number of defects were generated when using the conventional cut method along 45°, 90°, and the climb cut method along 90°. Few internal defects were observed when using the climb cut method along 45°; however, the machined surface was very rough. The mechanism for these phenomena was investigated by studying surface observations and cutting force, in addition to X-ray CT imaging. These results indicate that X-ray CT is a powerful tool for visualizing internal defects in CFRP, which differ significantly based on the direction of the fiber and machining method used.
关键词： Carbon fiber reinforced plastics,Surface roughness,Milling,Internal defect,X-ray computed tomography
更新于2025-09-16 10:30:52
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[IEEE 2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC) - Fukuoka, Japan (2019.7.7-2019.7.11)] 2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC) - Infrared- Thermometer-Based Detection of Optical Fiber Breakage in Structure
摘要： We show that infrared thermometry can be exploited to detect breakage points of optical fibers embedded in structures. This method has such advantages as real-time operation, cost efficiency, and visual display on site.
关键词： infrared thermometry,carbon fiber-reinforced plastics,structural health monitoring
更新于2025-09-11 14:15:04