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

• Applicant: Dr.-Ing. Pawel Kostka
• Subject Area: Mechanics ; Lightweight Construction, Textile Technology
• Term: from 2016 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 315011510

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.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1897: Calm, Smooth and Smart - Novel Approaches for Influencing Vibrations by Means of Deliberately Introduced Dissipation
• Co-Investigator: Professor Dr.-Ing. Niels Modler