Complex-Shaped Lightweight Structures with Adaptive Dynamic Behaviour through Evanescent Morphing

一致地实施轻量化设计原则是实现未来车辆、机器和设施的能源效率提高和新的性能水平的重要先决条件之一。一个有希望的解决方案是应用纤维增强聚合物(FRP)，与传统的整体式材料相比，可以实现高质量的节省。增强纤维的轻质、优化和负载适应分布实现了高强度和高刚度，但通常会导致部件的机械阻尼较低。同时，在现代设计解决方案中，减少了在系统级造成耗散的节点数量。由此产生的振动敏感性问题，即使在低激励水平下也会产生异常或过度的噪声，现在可以通过二次被动或主动减振措施来限制FRP结构的轻量化潜力。因此，所请求的项目的目标是开发用于基于射流驱动原理的逝去变形的轻质结构自适应振动控制的新的、几乎重量中性的系统的基本原理。这里介绍的术语“渐变”是指这种微小的形状变化，它只影响所考虑的振动结构的动力特性，而对结构的主要承载功能的影响可以忽略不计。为了有效地控制系统的动态行为，提出了可压缩约束层阻尼(CCLD)的概念。这种剪切粘弹性层以材料和工艺兼容的方式集成在部件的内部，具有由流体驱动控制的厚度，并构成具有可变阻尼和刚度的自适应元件。要实现FRP结构实现流体激活的CCLD，必须解决几个科学任务。首先，将利用在不同泡沫上进行的适应材料特性实验的结果来阐述和参数化在CCLD中发生的耗散机制的模型。其次，将创建承载各向异性玻璃钢结构的数值模型，并将其与先前阐述的CCLD模型合并，从而能够识别由于流体驱动而产生的变形场。第三，后一种模型将被CCLD的FRP方向相关阻尼性和压力相关阻尼性所增强。最后，将考虑可变的CCLD参数和由于驱动几何变化而可能产生的结构效应，对宽幅值和频率范围内的整体阻尼行为进行系统的数值研究。结果将在项目期间制造的通用演示器的实验测试中得到验证。

A consistent implementation of lightweight design principles is one of the important prerequisites for the achievement of improved energy efficiency and new performance levels of future vehicles, machines, and facilities. A promising solution is the application of fibre-reinforced polymers (FRP) with "tailored" reinforcement enabling high mass savings compared to the conventional monolithic materials. The lightweight optimal and load adapted distribution of reinforcing fibres enables high strength and stiffness but typically leads to low mechanical damping of components. At the same time, number of joints contributing to the dissipation at the system level, is reduced in modern design solutions. The resulting problematic vibration susceptibility, unusual or excessive noise emission even at low excitation levels are nowadays addressed by secondary passive or active damping measures limiting the lightweight potential of FRP structures.The objective of the requested project is therefore the development of fundamentals for modelling and dimensioning of novel, almost weight-neutral systems for adaptive vibration control of lightweight structures based on evanescent morphing using fluidic actuation principles. The here introduced term "evanescent morphing" means such a small shape change that only influences the dynamic behaviour of the considered vibrating structure whereas its effect on the primary load carrying function of the structure is negligible. For an effective controllability of the dynamic behaviour, a novel concept called Compressible Constrained Layer Damping (CCLD) is proposed. Such sheared viscoelastic layer, integrated in the inward of a component in a material and technology compatible manner, has thickness controlled by the fluidic actuation and constitutes an adaptable element with variable damping and stiffness.For the realisation of FRP structures implementing fluidically activated CCLDs, several scientific tasks must be solved. First, models of dissipative mechanisms occurring in the CCLD will be elaborated and parametrised using results of adapted material characterising experiments conducted on different foams. Second, numerical models of the load bearing anisotropic FRP structures will be created and merged with the previously elaborated models of the CCLD, enabling the identification of deformation fields due to fluidic actuations. Third, the latter models will be enhanced by the direction dependent FRP damping properties and pressure dependent damping properties of the CCLD. Finally, a systematic numerical investigation of the overall damping behaviour in broad amplitude and frequency range will be conducted taking into account both the variable CCLD parameters and possible structural effects due to actuated geometry change. The results will be validated in experimental tests on generic demonstrators manufactured during the project.