A contribution to a wedge shaped load introduction in highly stressed fiber polymer composite structures

在设计高分子纤维复合材料时，将高载荷引入结构元件是最核心的问题。原因如下：一方面，由于材料强度高，只存在薄厚度。另一方面，材料的各向异性使设计更加复杂。由于载荷引入区域内的力流通常横向流向纤维，较低的刚度和强度导致早期失效。由于装配的原因，通常需要更换另一种材料。这意味着必须考虑两种材料的不同性质。楔形连接描述了一种将集中载荷引入复合结构的解决方案，这种结构能够承受非常高的载荷，并且其形状是安全的，可以激发信心。为了充分利用纤维取向的极高强度，在楔形区域内均匀的负载分布是必要的。特别是楔形区域交点处的高局部压力载荷导致楔形断裂（断裂模式C）的早期破坏。因此，它定义了整个连接的可转移负载。在leichbau和Bauweisen的主持下，已经进行了理论和实践的试点测试。这样做有可能通过以下措施增加楔形连接的失效载荷：-楔形角度的变化，夹紧长度和楔形半径-由不同材料组成的芯的插入-楔形图案制造的优化-横向内夹板的插入另一个有趣的变化是楔形连接作为旋转对称结构。通过这样做，由纤维聚合物复合材料制成的管道连接可以集成在管道内。在提交的项目框架内，增加楔形破坏载荷的措施必须建立在坚实的基础上。主要目标是明确扩展和深化目前的结果，并找到优化的解决方案。此外，还必须对楔形设计进行实验验证。此外，有必要将矩形截面楔形连接的结果推广到旋转对称管连接中。更重要的目标是为使用纤维聚合物复合材料的设计工程师提供规则，并为楔形连接的最大承载能力提供数据。

The introduction of high loads into structural elements mostly is the core problem while designing with fiber polymer composites. The reasons are as followed: On the one hand only thin thicknesses exist because of the high strength of the material. On the other hand the anisotropy of the material makes design more complex. Due to the fact that the force flow within load introduction areas often runs transverse to the fiber, the lower stiffnesses and strengths lead to an early failure. Because of assembly reasons mostly a change to another material gets necessary. That means that the different properties of two materials have to be considered.The wedge connection describes a solution for introducing concentrated loads into composite structures which is capable to bear very high loads and by its shape is closure safe and inspires confidence. A uniform load distribution within the wedge area is necessary in order to take advantage of the extremely high strengths in fiber orientation. In particular the high local pressure load within the intersection to the wedge area causes early failure by wedge fracture (fracture mode C). Consequently it defines the transferable load of the entire connection.At the chair Konstruktiver Leichtbau und Bauweisen theoretical and practical pilot tests have already been conducted. In doing so it was possible to increase the failure load of the wedge connection by the following measures:- Variation of the wedge angle, the clamp length and the wedge radius- Insertion of cores consisting of different materials- Optimisation of the wedge pattern manufacturing- Insertion of transverse inner-pliesAnother interesting variation is the wedge connection as rotation-symmetric construction. By doing so tube connections made from fiber polymer composites can be integrated within tubes.In the framework of the submitted project the measures to increase the failure load of wedges have to be put on a firm basis. The primary objective is to clearly extend and deepen the present results and finding optimised solutions. In addition an experimental validation of the wedge design has to be conducted. Furthermore it is necessary to transfer the results of the wedge connection with rectangular cross section to rotation-symmetric tube connections.The superior objective is to give rules to the design engineers working with fiber polymer composites and to make data available for the maximal load capacity of wedge connections.