6月29号下午力学系和湍流与复杂系统重点室报告-两场报告
发布时间: 2010-06-23 04:37:00
SEMINAR SERIES
北京大学工学院 
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力学与空天技术系
湍流与复杂系统国家重点实验室
报告一：Temperature Dependence on Fiber Breakage Accumulation under Tensile Loading for Unidirectional CFRP Laminates
报告人： Prof. Junji NODA
Dept. of Mech. Eng., Yamaguchi Univ, Japan, e-mail: nodaj（at）yamaguchi-u.ac.jp
Abstract: The temperature dependence on the tensile damage process as well as the tensile strength in unidirectional carbon fiber reinforced plastics (CFRP) laminates was investigated experimentally and numerically. The constant strain rate tensile tests for CFRP laminates were carried out at room temperature (RT) and 120oC. The damage process under tensile loading was recorded by using a digital microscope to comprehend the accumulation of fiber breakages observed with increasing strain. The fiber breakages observed under tensile loading increase strongly in the vicinity of ultimate failure load and this behavior depresses with increasing temperature. The clusters of fiber breakages formed at RT could not be observed at 120oC. These experimental results lead to the fact that the number of fiber breakages and the existence of cluster of fiber breakages were influenced by the temperature dependent stress-strain relation of matrix resin. Then, a new simulation based on finite element model considering the stress-strain relation of matrix resin was proposed. In this model, the matrix was assumed to be an elasto-plastic creep body and the Monte Carlo simulation was conducted in order to simulate the fiber breakages. As results, the damage process and strength predicted numerically by the proposed simulation agree well with experimental results. Therefore, the temperature dependent mechanism for the damage process including the generation of clusters as well as the strength were quantitatively cleared.
About the speaker
PRESENT POSITION: Assistant Professor, Materials Reliability Engineering Lab., Department of Mechanical Engineering, Yamaguchi University, Tokiwadai 2-16-1, Ube 755-8611, Japan
EDUCATION: Mar. 1999, Bachelor of Engineering, Keio University, Yokohama, Japan;
Mar. 2001, Master of Engineering, Keio University, Yokohama, Japan
Sep. 2004, Doctor of Engineering, Keio University, Yokohama, Japan
AWARDS: Best paper authors in 2003 awarded by the Japan Society for Composite Materials
主持人：方岱宁 教授
时 间：6月29日（周二）下午2:30
地 点：力学楼434会议室
欢迎广大师生光临！联系人：裴永茂 82529980
报告二：Strength Evaluation of unidirectional CFRP with a local off-axis fibers array
报告人： Prof. Koichi Goda
Dept. of Mech. Eng., Yamaguchi Univ, Japan
Abstract: CFRP (Carbon fiber reinforced plastics) exhibit superior mechanical properties, and are recently applied to large structural materials using the VaRTM(Vacuum assisted Resin Transfer Molding) method. In the vicinity of the resin inlet of this method, and at the joint of CFRP structures, it is pointed out that the disorder in fiber orientation often occurs. In this study, therefore, the effect of local off-axis fibers array on the tensile properties of unidirectional CFRP was basically investigated. An experimental device for making a local off-axis fibers array on a CFRP lamina was newly developed, and various unidirectional CFRP laminae were prepared by changing the fiber orientation angle and the size. The results show that the tensile strength of CFRP laminae with off-axis fibers array decreases with increasing the fiber orientation angle and the length, and depends on the degree of fiber bundle waving. On the other hand, Young’s moduli of the CFRP lamnae show an almost constant value, which is relatively close to that of CFRP lamina without off-axis fibers array. Finally, Young’s moduli and tensile strength of the CFRP laminae were analyzed from a proposed composite model with an off-axis fibers array, and its validity was discussed.
About the speaker
PRESENT POSITION: Professor, Materials Reliability Engineering Lab., Department of Mechanical Engineering, Yamaguchi University, Tokiwadai 2-16-1, Ube 755-8611, Japan
EDUCATION: Mar. 1980, Bachelor of Engineering, Hiroshima University, Hiroshima, Japan
Mar. 1982, Master of Engineering, Hiroshima University, Hiroshima, Japan
Nov. 1989, Doctor of Engineering, Hiroshima University, Hiroshima, Japan
AWARDS: Award of Encouragement by The Japan Society of Mechanical Engineers (1992)
Award of Encouragement by The Society of Materials Science, Japan (1996)
Excellent Paper Awards by The Society of Materials Science, Japan (1998)
主持人：方岱宁 教授
时 间：6月29日（周二）下午3:30
地 点：力学楼434会议室
欢迎广大师生光临！联系人：裴永茂 82529980