Papers by Author: Isamu Ohsawa

Abstract: We have developed a novel fiber-optic vibration sensors and applied commercially available strain and temperature sensors to health monitoring of composite structures. In this study, we constructed an optical fiber network integrating four types of optical fiber sensor into a carbon reinforced plastic (CFRP) panel. These four sensors were the vibration sensor developed by our laboratory, two distributed sensors based on Brillouin and Raman backscattering and Fiber Bragg Grating (FBG) sensors. By dealing the data obtained from the measurement systems corresponding to these four sensors, strain/stress and temperature distributions throughout the panel can be monitored. Vibration and elastic waves transmitting on the panel are also detected at several sensing points. Furthermore, we will be able to determine damage locations and modes by processing the wave signals. To make the panel with the optical fiber sensor network more sensitive and smarter, we are developing some techniques that can improve the performance of the sensors and can assess the structural integrity by analyzing measurement results. In this paper, the development of the first generation of our smart composite panel with the optical fiber sensors is described and the techniques making the panel more sensitive and smarter are also described.

Abstract: This paper presents the adaptation of the analytical method for transverse laminacracking in multidirectionally laminated composites to the finite element method. The damageinitiation and extension in a structure made of the laminated composite are evaluated by thedeveloped finite element method. The reduction in the stiffness of the laminated composite thatcaused by the crack growth is evaluated by the total force method. In the present analyses by thedeveloped method, the critical strain of the crack growth is the value of the strain which satisfiesboth energy criterion and stress criterion. To demonstrate the accuracy of the developed method,the analytical results of crack growth in CFRP quasi-isotropic laminate with a circular hole arecompared with experimental results.