국내 최대 기계 및 로봇 연구정보

기술보고서

기술보고서 게시판 내용
타이틀	Examination of Quantitative Infrared Stress Measurement of CFRP Laminates and Its Application to Non-Destructive Evaluation
저자	SUGIMOTO Sunao, ISHIKAWA Takashi
Keyword	Infrared Stress Measurement; Theoretical Calibration; Unsteady Heat Conduction; Multi-Ply Laminate; Carbon-Epoxy
URL	http://send.nal.go.jp/send/jpn/dlpdf.php3/naltr0001396.pdf?id=NALTR0001396
보고서번호	NAL TR-1396
발행년도	1999.12
출처	NAL (National Aerospace Laboratory of Japan)
ABSTRACT	The infrared stress measurement technique was applied to the qualitative measurement of stress in carbon fiber reinforced plastic (CFRP) composites; the main advantages of this measurement method being its in-situ and non-contact nature. As a first step, thermoelastic constants were obtained for unidirectional CFRP (UD-CFRP) using the infrared stress measurement system. The resulting values were compared with thermoelastic constants derived using basic equations. As a consequence, the reliability of the measured thermoelastic constants was established and the effectiveness of this measurement system for quantitative stress measurement was confirmed. The temperature dependency of the transverse coefficient of thermal expansion and specific heat at constant stress in UD-CFRP were also demonstrated to have a tendency to cancel one another out so as to decrease the temperature dependency of the thermoelastic constant. Such a finding was considered to be an advantage of the infrared stress measurement technique for CFRP. In addition, other influential factors on measurement were examined. Regarding the infrared stress measurement for multi-ply CFRP laminates, one important issue is to evaluate the effect of heat conduction from internal plies where heat is produced as a result of the thermoelastic effect. Although the heat flux from internal plies as a result of the thermoelastic effect and applied loading has the same frequency, the infrared stress measurement system allows the surface temperature amplitude to be synchronized with the loading. The heat conduction effect for multi-ply CFRP laminates was evaluated numerically based on an analytical equation and FEA. These calculated values were compared with those obtained from infrared stress measurement. A high degree of coincidence between theoretical, FEA, and experimental results was obtained. It was clearly shown that thermal conduction must be considered in the infrared stress measurement of multi-ply CFRP should the surface layer be a ply with a low thermoelastic constant. Finally, some examples of applications of this technique to the non-destructive evaluation of CFRP laminates have also been presented.