Local buckling of shear-deformable composite laminated beams with flanges and webs made of unsymmetrically layered laminates

翼缘和腹板由不对称层合板制成的剪切变形复合材料层合梁的局部屈曲

• 批准号: 421986570
• 负责人: Professor Dr.-Ing. Christian Mittelstedt
• 金额: --
• 依托单位: Fachgebiet Konstruktiver Leichtbau und Bauweisen
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/421986570?language=en
• 关键词: Local; buckling; shear; deformable; composite

Composite structures in the form of thin laminated plates or shells have found an increasing use in many different branches of engineering science, e.g. in aerospace or automotive engineering, but also in civil engineering applications over the last few decades. Due to their excellent specific strength and stiffness properties, composite laminates or shells are prominently found in lightweight engineering applications. Generally, composite laminates are layered plates or shells consisting of anisotropic and unidirectionally fiber-reinforced layers, e.g. carbon or glass fibers in a plastic matrix.In civil engineering applications, the most basic structural elements are prismatic beams under axial and bending load. Due to their slenderness and their overall thin-walled nature, stability problems such as global buckling (i.e. flexural buckling, flexural-torsional buckling and lateral buckling) as well as local buckling need to be taken into account. The current research project is devoted to the investigation of local buckling problems, i.e. the local buckling of flanges and webs of thin-walled composite laminated beams. For this purpose, discrete plate models shall be used in which webs and flanges are considered as being separate plates considering elastic clampings at those locations where adjacent beam segments intersect. Besides purely closed-form analytical solutions using the Rayleigh quotient employing adequate shape functions for all relevant buckling degrees of freedom, series expansions in conjunction with the Ritz method will enable the analysis and investigation of the local buckling behavior of composite laminated beams under consideration of transverse shear deformations and typical coupling effects as they occur in composite laminates. Specifically, bending-extension coupling in the case of unsymmetric laminates as well as bending-twisting coupling in the case of non-orthotropic laminate layups shall be taken into account explicitly. To this day, no investigations are available that would treat these effects in a systematic manner so that a significant requirement for research exists. Once adequate methods for the local buckling analysis have been developed, the buckling problem will be transformed into an optimization problem. By means of mathematical programming and nonlinear optimization, beam designs will be determined which exhibit the highest possible buckling resistance which is an important factor for any practical application where composite laminated beams are employed. Lastly, all developed analysis methods and the main buckling characteristics will be validated by sys-tematic buckling experiments.

在过去的几十年里，薄层板或壳形式的复合结构在工程科学的许多不同分支中得到了越来越多的应用，例如在航空航天或汽车工程中，以及在土木工程应用中。由于其优异的比强度和刚度性能，复合层压板或壳在轻量化工程应用中占有突出地位。一般来说，复合层压板是由各向异性和单向纤维增强层组成的层状板或壳，例如塑料基体中的碳或玻璃纤维。在土木工程应用中，最基本的结构单元是柱体梁，承受轴向和弯曲荷载。由于它们的长细和整体薄壁性质，需要考虑全局屈曲（即弯曲屈曲，弯曲-扭转屈曲和侧向屈曲）以及局部屈曲等稳定性问题。本课题主要研究薄壁复合材料层合梁的局部屈曲问题，即翼缘和腹板的局部屈曲问题。为此，在离散板模型应使用中，腹板和法兰被认为是独立的板，在相邻梁段相交的位置考虑弹性夹紧。除了使用瑞利商对所有相关屈曲自由度采用适当形状函数的纯封闭形式解析解外，级数展开与里兹方法相结合，将能够分析和研究复合材料层合梁在考虑横向剪切变形和复合材料层合板中发生的典型耦合效应时的局部屈曲行为。具体而言，应明确考虑非对称层合板的弯曲-拉伸耦合以及非正交异性层合板的弯曲-扭转耦合。到目前为止，还没有任何研究可以系统地处理这些影响，因此有必要进行大量的研究。一旦研究出适当的局部屈曲分析方法，屈曲问题将转化为优化问题。通过数学规划和非线性优化，梁的设计将被确定为具有最高的抗屈曲能力，这是任何实际应用中使用复合材料层合梁的一个重要因素。最后，将通过系统的屈曲实验对所建立的分析方法和主要屈曲特征进行验证。