Stress Analysis in Composite Structures

建议：DMS-0406374 PI：罗伯特·利普顿机构：路易斯安那州立大学标题：应力分析复合结构。预计该项目的结果将提供与微观尺度的应力波动相关的失效标准与平均或宏观应力和应变之间的必要联系，这些应力和应变可以使用放置在复合结构部件边界上的应变计来测量。 将进行分析的周期性微结构，随机微结构，和微结构与G或H收敛序列的解算子的线性和非线性椭圆边值问题。在这个项目中，一个阶梯的日益复杂的连续模型，包括预应力和非线性弹性和弹塑性行为将被纳入应力评估方法。这一点至关重要，因为工程和天然生物复合材料结构是预应力结构，在高应力区域附近通常表现出非线性弹性行为。复合材料正日益成为要求材料具有高比强度和刚度的结构应用的首选材料。 现代设计实践越来越多地采用由复合材料子结构组成的承载部件，这些子结构通过粘接或螺栓连接。这种趋势可以在最新的飞机、船舶和汽车上看到。例子包括空中客车A300- 600 R和波音777，其特点是复合材料垂直尾翼。尾翼的部件用螺栓连接在一起，并通过U形夹固定在机身上。这是中央利益，能够理解和预测的模式，在这些结构的故障启动。这需要对机械载荷如何在典型复合结构中的尺度层次上分布有基本的了解。 在这个项目中，研究人员和他的同事将致力于新的严格和系统的方法，以准确的应力评估跨长度尺度。这些方法将被用于新的计算方法的分层复合材料结构的设计，对冲失败。在这里，通过优化复合材料微观结构的定制，将故障的机会降到最低。

Proposal: DMS-0406374PI: Robert LiptonInstitution: Louisiana State UniversityTitle: Stress Analysis in Composite Structures.ABSTRACTThe objective of this investigation is to develop a rigorous method for the stress analysis of composite structures. It is anticipated that the results of this project will provide the necessary link between failure criteria related to stress fluctuations at the micro-scale and the averaged or macroscopic stress and strain that can be measured using strain gauges placed on the boundary of a composite structural component. The analysis will be carried out for periodic microstructures, random microstructures, and microstructures associated with G or H convergent sequences of solution operators to linear and nonlinear elliptic boundary value problems. In this project a ladder of increasingly sophisticated continuum models incorporating pre-stress and nonlinear elastic and elastic-plastic behavior will be incorporated into the stress assessment methodology. This is crucial as engineering and naturally occurring bio-composite structures are pre-stressed and often exhibit nonlinear elastic behavior near regions of high stress.Composite materials are increasingly becoming the materials of choice for structural applications that require materials with high specific strength and stiffness. Modern design practice increasingly incorporates the use of load bearing components made up of composite substructures that are connected through bonded or bolted joints. This trend can be seen in the latest aircraft, ships and automobiles. Examples include the Airbus A300-600R and the Boeing 777 that feature a composite vertical tail. Components of the tail are bolted together and secured to the fuselage through clevises. It is of central interest to be able to understand and anticipate the modes of failure initiation in these structures. This requires fundamental understanding of how the mechanical loads are distributed across the hierarchy of scales seen in a typical composite structure. In this project the investigator and his colleagues will work on new rigorous and systematic methods for accurate stress assessment across length scales. These methods will be employed in novel computational methods for the design of hierarchical composite structures that hedge against failure. Here the opportunity for failure will be minimized through optimal tailoring of the composite microstructure.