Recently, composite materials have been mainly used in the main wings, ailerons, and fuselages of aircraft and rotor blades of helicopters. Composite materials used in rapid moving structures are subject to impact by hail, lightning, and bird strike. Such an impact can destroy fiber tissues in the c...
Recently, composite materials have been mainly used in the main wings, ailerons, and fuselages of aircraft and rotor blades of helicopters. Composite materials used in rapid moving structures are subject to impact by hail, lightning, and bird strike. Such an impact can destroy fiber tissues in the composite materials as well as deform the composite materials, resulting in various problems such as weakened rigidity of the composite structure and penetration of water into tiny cracks. In this study, experiments were conducted using a 2 kW halogen lamp which is most frequently used as a light source, a 2 kW near-infrared lamp, which is used for heating to a high temperature, and a 6 kW xenon flash lamp which emits a large amount of energy for a moment. CFRP composite sandwich panels using Nomex honeycomb core were used as the specimens. Experiments were carried out under impact damages of 1, 4 and 8 J. It was found that the detection of defects was fast when the xenon flash lamp was used. The detection of damaged regions was excellent when the halogen lamp was used. Furthermore, the near-infrared lamp is an effective technology for showing the surface of a test object.
Recently, composite materials have been mainly used in the main wings, ailerons, and fuselages of aircraft and rotor blades of helicopters. Composite materials used in rapid moving structures are subject to impact by hail, lightning, and bird strike. Such an impact can destroy fiber tissues in the composite materials as well as deform the composite materials, resulting in various problems such as weakened rigidity of the composite structure and penetration of water into tiny cracks. In this study, experiments were conducted using a 2 kW halogen lamp which is most frequently used as a light source, a 2 kW near-infrared lamp, which is used for heating to a high temperature, and a 6 kW xenon flash lamp which emits a large amount of energy for a moment. CFRP composite sandwich panels using Nomex honeycomb core were used as the specimens. Experiments were carried out under impact damages of 1, 4 and 8 J. It was found that the detection of defects was fast when the xenon flash lamp was used. The detection of damaged regions was excellent when the halogen lamp was used. Furthermore, the near-infrared lamp is an effective technology for showing the surface of a test object.
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제안 방법
2. As for the transmission method, the pilot experiment showed that no damage was found regardless of light sources, and thus only the reflection method was used. Perhaps the possibility of defect detection will increase, that CFRP specimen thickness is thinner than 2 mm and the honeycomb core thickness is than 12.
While as for metal structures, external impact has the effect of elastic deformation or plastic deformation on the structures, as for composite materials, impact load can lead to the phenomenon of fiber tissue destruction as well as deformation in the composite materials, resulting in the problems of the weakened rigidity of composite structures, water penetration into a tiny crack and so on [4]. Hence, this study applied impact load to CRFP composite specimens by using the infrared thermography technology [5] and different light sources, and then investigated a method for detecting damage to composite materials more quickly and more accurately.
Defect detection methods through infrared thermography can be largely divided into two kinds, passive methods and active methods. The method used for this experiment was lock-in infrared thermography method out of all the active methods, and it can calculate the size of defects by taking a particular stimulus as harmonic function and conveying it to the target object and then processing the response signals from the target object. To detect defects effectively, the lock-in phase technique was applied to the experiment, Active infrared thermography inspection is a method of detecting thermal energy emitted from the inspection object when energy is applied to an inspection object [6].
This study investigated a method for detecting damage to CFRP composite material specimens to which impact energy was applied by using the halogen lamp, the near-infrared lamp, and the xenon flash lamp. And as a result, the following conclusion was drawn.
대상 데이터
For this reason, 200 mHz was selected. As an infrared thermal-imaging camera, this study used Silver 420 m Model (NETD:25 mK) made by French Cedip Company.
For the fabrication of impact test specimens, experiment was conducted by increasing impact from 1 J to 4 J and 8 J with an impact tester of drop impact type (Instron 9350), which is operated at KOLAS accredited institutions. The circumference of the impact tester's hammer was 20 mm.
1, and were fabricated as sandwich panels with honeycomb structure being inserted between the composite materials. For the materials of the composite, ARRIS 3K prepreg and T 300 UD were used, and plain-weave prepreg was bonded before and after UD prepreg. For the specimen 2 mm in thickness, CFRP was laid up to form 9 layers, and for 3 mm, it was laid up to form 12 layers.
Composite materials can be fabricated in a variety of forms according to the weaves of fiber tissues, and in the case of aircraft structures, composite materials in the form of plain weave are mostly used. Hence, this study used the composite materials 2.06 mm (2 mm) and 3.03 mm (3 mm) in thickness fabricated in the form of plain weave. The specimens were made in the size of 60 mm ×60 mm to fit the measurable size of the impact tester, as shown in Fig.
The composite material used in the experiment was CFRP. Composite materials can be fabricated in a variety of forms according to the weaves of fiber tissues, and in the case of aircraft structures, composite materials in the form of plain weave are mostly used.
The specimens were made in the size of 60 mm ×60 mm to fit the measurable size of the impact tester, as shown in Fig. 1, and were fabricated as sandwich panels with honeycomb structure being inserted between the composite materials.
To detect defects effectively, the lock-in phase technique was applied to the experiment, Active infrared thermography inspection is a method of detecting thermal energy emitted from the inspection object when energy is applied to an inspection object [6]. Three types of light sources were used for the experiment. The first one was a 2 kW light source, the second one was a 2 kW near-infrared lamp, and the third one was a 6 kW xenon flash lamp.
이론/모형
In the case of a xenon lamp, a temperature image by a short pulse method which cannot use the lock-in thermography technique was used. The experiment was carried out by using the reflection method, as shown in Fig. 2. As for the transmission method, the pilot experiment showed that no damage was found regardless of light sources, and thus only the reflection method was used.
성능/효과
3) It was found that damage detection with the near-infrared lamp is an effective technology for identifying the surface of a test object, though inferior to the halogen lamp and the xenon lamp.
참고문헌 (9)
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