Recently, advanced composite materials as represented by carbon fiber reinforced plastics (CFRP) have been used in many fields including aerospace field. CFRP have the good feature of mechanical properties with the higher specific strength and specific rigidity as compared with metallic materials, and have excellent properties in electrical property and thermal characteristics.
On the other hand, evaluating the dynamic behaviors and the strength characteristics of CFRP structures is much more complex than metallic material. Mechanical properties of composite structures decrease by external impact events since the interlaminar fracture toughness of composite materials is low. By impact load caused by fall of the machine tool for composite structures, internal damages such as delamination, fiber breakage, and matrix crack which are difficult to detect from the surface are easily caused.
It is necessary to find those internal damages by the nondestructive inspection in order to avoid a remarkable decrease in the rigidity and strength of the structures. Usually, the nondestructive inspection method using ultrasonic wave or X-ray has been used for the detection of damages in composite materials, but the method is labor-intensive and cannot disregard the existence of a human error.
Recently, the technology that is called a structural health monitoring has been developed remarkably, and the research has been actively done. The structural health monitoring is the technology that automatically observes the health state of the structure using measurement information from the sensor built into the structure. Especially, information on the impact load that causes damages is very important for working an effective diagnosis and an evaluation of the structure safety. If information on the maximum impact load and the impact energy is obtained in real time, the occurrence of the impact damage can be predicted.
Thus, when monitoring the impact load from the sensor response becomes possible in real time, structural health can be evaluated automatically, and great improvement of the structure safety becomes possible.
The present paper discusses an experimental identification method of impact load acting CFRP plates. Especially the present paper develops damage monitoring of CFRP plates based on the impact force identification.
edited by Yuki MIURA