Critical Time to Instability of Viscoelastic Structures

在AIAA SciTech 2014会议的主题演讲中，洛克希德·马丁航天系统公司的执行副总裁鼓励观众停止将复合材料视为“黑铝”。另一位发言者，约翰霍普金斯大学应用物理实验室空间部门负责人说，该行业正在设计“用复合材料制成的铝制飞机”。为了充分发挥复合材料在航空航天领域的优势，减少其缺点，需要新的理论和方法。 一种理论是粘弹性结构失稳的临界时间。这一理论在通用航空领域有直接的应用，因为许多飞机都是玻璃纤维增强塑料，未来在商用飞机领域的应用将继续增加复合材料的使用。临界时间理论的另一个直接应用领域是核反应堆部件评估，因为反应堆内的高温会在金属部件中产生粘弹性响应。申请人已经开发了一种分析方法来估计粘弹性结构变得不稳定所需的时间，利用申请人在玻璃纤维增强塑料飞机的使用寿命和CANDU核反应堆中螺旋线圈的稳定性领域中的现有创新研究。 建议的研究计划是确认复杂的，分析理论，使用文献中的例子，并辅以实验。一旦得到证实，该理论将被推广以适应更复杂的结构。长期目标是推进理论，包括非线性和大变形。实验将由四名理科硕士学生在五年的时间内使用申请人研究小组内现有的载荷框架和光弹性设备进行。与此同时，一名博士生将致力于现有临界时间理论的推广，以包括三维结构和时变载荷。这项为期五年的研究计划的成果将是一个有效的理论，用于航空航天和核工业。事实上，该理论的简化形式已被要求在2017年前在核工业中使用，因此该研究计划解决了加拿大工业的当前和未来需求。

During a keynote address at the AIAA SciTech 2014 conference, the executive vice president of Lockheed Martin Space Systems encouraged the audience to stop treating composites as `black aluminum'. Another speaker, the head of the space sector at Johns Hopkins University's Applied Physics Laboratory, said that the industry is designing `aluminum airplanes out of composites'. To fully exploit the advantages and minimize the disadvantages of composite materials in the aerospace field, new theories and approaches are needed. One theory is the critical time to instability of a viscoelastic structure. This theory has immediate applications in the field of general aviation as a number of aircraft are glass fibre-reinforced plastic, and future applications in the commercial aircraft sector where composite material use continues to increase. Another field for immediate use of the critical time theory is nuclear reactor component assessment because the elevated temperatures within a reactor produce a viscoelastic response in the metallic components. The applicant has developed an analytical method to estimate the time needed for a viscoelastic structure to become unstable, drawing on existing, innovative research by the applicant in the fields of service lives of glass fibre-reinforced plastic aircraft and the stability of helical coils in CANDU nuclear reactors. The proposed research program is to confirm the complex, analytical theory using examples from the literature and supplemented by experiments. Once confirmed, the theory is to be generalized to accommodate more sophisticated structures. The long term objective is to advance the theory to include nonlinearities and large deformations. The experiments will be conducted by four M.A.Sc students over the course of five years using existing load frames and photoelastic equipment within the applicant's research group. In parallel, one PhD student will work on the generalizations of the existing critical time theory to include three-dimensional structures and time varying loads. The outcome of this five year research program will be a validated theory for use in the aerospace and nuclear industries. Indeed, a simplified form of the theory has been requested for use in the nuclear industry by 2017 thus this research program addresses immediate and future needs of Canadian industry.