Stress Analysis in Composite Structures

建议：DMS-0406374PI：Robert Lipton研究所：路易斯安那州立大学标题：复合材料结构中的应力分析。本研究的目的是发展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与微观应力波动有关的失效标准和可使用放置在复合材料结构部件边界上的应变计测量的平均或宏观应力和应变之间建立必要的联系。对线性和非线性椭圆型边值问题的周期微结构、随机微结构以及与G或H收敛的解算子序列相关的微结构进行分析。在这个项目中，一个越来越复杂的连续体模型的阶梯，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，因为工程和自然产生的生物复合材料结构都是预应力结构，往往在高应力区附近表现出非线性弹性行为。复合材料越来越成为结构应用的首选材料，这些应用对材料的比强度和刚度提出了更高的要求。现代设计实践越来越多地采用由复合子结构组成的承重部件，这些部件通过粘结或螺栓连接连接在一起。这一趋势可以在最新的飞机、船舶和汽车中看到。例子包括空客A300-600R和波音777，它们具有复合垂直尾翼。机尾的部件用螺栓固定在一起，并通过夹头固定在机身上。能够理解和预测这些结构中的失效起始模式是非常有意义的。这需要从根本上理解机械载荷是如何在典型的复合材料结构中的尺度层次上分布的。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，以在长度尺度上进行准确的压力评估。这些方法将被用于设计避免失效的层次化复合材料结构的新的计算方法。在这里，通过对复合材料微观结构的优化剪裁，可以最大限度地减少失败的机会。

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.