报告题目： Composites under Harsh Environments: Civil Engineering and Aerospace Engineering perspectives
报告人：许大卫（David Hui）教授
时间：2014年5月31日16:00
地点：南一楼东北角三楼力学系会议室
邀请人：胡洪平副教授
主讲人简介：
教育部2011-2015年度海外名师项目获得者，美国新奥尔良大学终身教授，ASME Fellow，国际著名复合材料杂志COMPOSITES PART B：ENGINEERING主编，复合材料界重要的国际学术会议ICCE（INTERNATIONAL CONFERENCE ON COMPOSITES or NANO ENGINEERING）的会议主席。迄今为止获得包括俄亥俄州立大学科学研究奖、ASME（American Society of Mechanical Engineers美国机械工程师协会) “ Ralph James”科学奖等各种科学奖项以及荣誉证书，获美国新奥尔良大学终生研究成果奖和新奥尔良大学研究教授（Research Professor）的称号；多次获得包括美国海军研究局（ORU），美国国家自然科学基金（NSF），美国海洋大气局（NOAA）在内的美国政府和企业的各种资助。
报告摘要：
The work presents an overview of the current state of the art in low temperature effects on materials in terms of durability and safety of vehicles. Susceptibility of composites to failure at low temperature is a critical issue for the aerospace industry. Spacecrafts operate at temperatures well below -200 deg C. High altitudes aircrafts routinely fly at -70 deg C to -100 deg C. These low temperatures result in two competing effects on composite stiffness. One beneficial effect involves increased stiffness because the polymer matrix would harden at low temperature. The other detrimental effect involves increased thermally-induced stress, which produces microcracks in matrix, which in turn, reduces the overall stiffness of the composites. These two competing beneficial-detrimental phenomena at the microstructure level have been studied for decades, but a quantitative understanding of the interplay of these two effects has continued to elude the researchers. Additional complexities arise when the stiffness increase effect is considered because of high strain rate loading. Long term exposure to cyclic or vibration can again reduce the stiffness. The competing effects for fatigue of fiber-reinforced polymer composites at low temperatures will be presented. Emphasis will be on civil engineering structural and other involving earthquake applications, orthogrids, FRP rebars, sandwich structures, guardrails, piers and structural members.
In order to study the effects of high temperatures, the whole range of temperatures from low temperatures -250 deg C to high temperatures up to Glass Transition Temperatures will be examined. This paper will address these issues using phenomenological models and experimental observations. The low temperature effects is the cause of Space Shuttle disaster, and Titanic Ship, and helicopter crashes, and numerous traffic hazards and accidents, thus, all design of vehicles, s or systems must be designed for low temperatures. As a complete analysis, this work also deals with high temperature failures, which is the reason for one other Space Shuttle accidents in reentry to atmosphere.
