| Summary: | 碩士 === 中正理工學院 === 兵器系統工程研究所 === 88 === Nondestructive evaluations of the epoxies film adhesion to the substrate of fiber reinforced composite laminates have been treated by using the ultrasonic testing. There are two parts in the research. One is the post-repair defects detection; the other is the adhesive strength evaluation. In the post-repair defects detection, two model specimens with external patch and single scarf patch have been prepared. Both of them are analyzed by pulse echo method and immersion through transmission method of ultrasonic testing. Designed and manufactured the reference standard, 6mm artificial debond defect was detectable. The results were present by A-scan and C-scan technologies. The ultrasonic testing procedures of post-repair of graphite/epoxy composite sandwich laminates have been established.
In the adhesive strength evaluation, the straight longitudinal wave attenuation technique has been used. Six model specimens with different values of adhesive strength have been prepared and analyzed experimentally. Three of these specimens have a strong adhered film to the substrate. They are simulated the depot level situation. The others have a weakly adhering film. They are simulated the field level situation. From the relative attenuation coefficient obtained by film adhesion thickness change and the frequency change, it has been found that attenuation coefficient of direct proportion with film adhesion thickness and linear formula with frequency. The reliability was above 95. To verify the adhesive strength, the single lap shear testing has been used. The result shows the more relative attenuation coefficient, the weaker adhesive strength under the same film adhesion thickness. Therefore, the linear formula and figure with frequency to evaluate adhesive strength have been confirmed to use.
The results of the research have provided practicable and complete post-repair defects detection methods, and adhesive strength evaluation of graphite/epoxy composite sandwich laminates by using ultrasonic testing
technologies.
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