Stress Analysis in Composite Structures

提案：DMS-0406374PI: Robert lipton机构：路易斯安那州立大学标题：复合材料结构的应力分析。摘要本研究的目的是建立一种严格的复合材料结构应力分析方法。预计该项目的结果将在微观尺度上与应力波动有关的失效标准与可使用放置在复合结构部件边界上的应变片测量的平均或宏观应力和应变之间提供必要的联系。分析将进行周期微结构，随机微结构，以及与线性和非线性椭圆边值问题解算子的G或H收敛序列相关的微结构。在这个项目中，一个包含预应力和非线性弹性和弹塑性行为的越来越复杂的连续体模型的阶梯将被纳入应力评估方法。这是至关重要的，因为工程和自然发生的生物复合材料结构是预应力的，并且经常在高应力区域附近表现出非线性弹性行为。复合材料正日益成为需要高比强度和刚度材料的结构应用的首选材料。现代设计实践越来越多地结合使用由复合子结构组成的承重部件，这些构件通过粘合或螺栓连接。这一趋势可以从最新的飞机、轮船和汽车上看到。空客A300-600R和波音777都采用了复合垂直尾翼。机尾的部件用螺栓连接在一起，并通过缝隙固定在机身上。能够理解和预测这些结构的失效启动模式是中心兴趣。这需要对典型复合材料结构中所见的机械载荷是如何跨层次分布的基本理解。在这个项目中，研究者和他的同事们将研究新的严格和系统的方法来准确地评估长度尺度上的应力。这些方法将用于设计防止失效的分层复合结构的新计算方法。通过优化复合材料微观结构，将失效的可能性降至最低。

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.