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Fiber reinforced epoxy resin composites are widely used in electrical power equipment. However, due to their complex preparation process and multi-layered structure, internal defects are prone to be introduced during manufacture, which may lead to partial discharge and even breakdown under long-term high voltage operating condition. Early detection of these defects can significantly reduce the occurrence of failures. In this paper, an ultrasonic testing system for composite was established on the basis of ultrasonic reflection method, and various plate samples of glass fiber reinforced epoxy resin composites containing artificial crack, delamination, and metal impurity defect were prepared on the basis of vacuum assisted resin infusion molding method. Ultrasonic testing and spectral analysis were then conducted on these defect-containing plate samples. The results indicate that there are significant differences in the ultrasonic reflection waveforms for different defects of samples. By transforming the ultrasonic echoes into frequency spectra, the normalized spectral characteristic curves are obtained, and different types of defects can be identified by calculating the characteristic values from these curves. The characteristic value of the sample with crack defect is the smallest, and the characteristic value of the sample with delamination defect is the largest.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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