Martin Wiedemann

DESIGN OF A SMART LEADING EDGE DEVICE FOR LOW SPEED WIND TUNNEL TESTS IN THE EUROPEAN PROJECT SADE

Purpose – The purpose of this paper is to describe the pre‐design and sizing of a smart leading edge section which is developed in the project SADE (Smart High Lift Devices for Next Generation Wings), which is part of the seventh framework program of the EU.Design/methodology/approach – The development of morphing technologies in SADE concentrates on the leading and trailing edge high‐lift devices. At the leading edge a smart gap and step‐less droop nose device is developed. For the landing flap a smart trailing edge of the flap is in the focus of the research activities. The main path in SADE follows the development of the leading edge section and the subsequent wind tunnel testing of a five meter span full‐scale section with a chord length of three meters in the wind tunnel T‐101 at the Russian central aero‐hydrodynamic institute (TsAGI) in Moscow.Findings – The presented paper gives an overview over the desired performance and requirements of a smart leading edge device, its aerodynamic design for the ...

Design of a Smart Leading Edge Device

To make use of low-drag future generation wings with high aspect ratio and low sweep for natural laminar flow, new high lift devices have to be developed [ACARE (Addendum to the Strategic Research Agenda, 2008), Horstmann (TELFONA, Contribution to Laminar Wing Development for Future Transport Aircraft, 2006)]. At the wing leading edge a smart e.g. morphing high lift device is being developed which provides a high-quality surface without gaps and steps. Due to the low maturity of morphing skins (Thill et al. (The Aeronautical Journal, 112:117–138)) the challenge of high strains has to be solved by an adequate design and sizing process. The presented design process comprises the requirements of a smart leading edge device, the structural pre-design and sizing of a full-scale leading edge section for wind tunnel tests.

Experimental and finite element analyses of multifunctional skins for morphing wing applications

As a consequence of operational efficiency because of rising energy costs, future transport systems need to be mission-adaptive. Especially in aircraft design the limits of lightweight construction, reduced aerodynamic drag and optimized propulsion are pushed further and further. The first two aspects can be addressed by using a morphing leading edge. Great economic advantages can be expected as a result of gapless surfaces which feature longer areas of laminar flow. Instead of focusing on the kinematics, which are already published in a great number of varieties, this paper emphasizes as major challenge, the qualification of a multi-material layup which meets the compromise of needed stiffness, flexibility and essential functions to match the flight worthiness requirements, such as erosion shielding, impact safety, lighting protection and de-icing. It is the aim to develop an gapless leading edge device and to prepare the path for higher technology readiness levels resulting in an airborne application. During several national and European projects the DLR developed a gapless smart droop nose concept, which functionality was successfully demonstrated using a two-dimensional 5 m in span prototype in low speed (up to 50 m/s) wind tunnel tests. The basic structure is made of commercially available and certified glass-fiber reinforced plastics (GFRP, Hexcel Hexply 913). This paper presents 4-point bending tests to characterize the composite with its integrated functions. The integrity and aging/fatigue issues of different material combinations are analyzed by experiments. It can be demonstrated that only by adding functional layers the mentioned requirements such as erosion-shielding or de-icing can be satisfied. The total thickness of the composite skin increases by more than 100 % when required functions are integrated as additional layers. This fact has a tremendous impact on the maximum strain of the outer surface if it features a complete monolithic build-up. Based on experimental results a numerical model can be set up for further structural optimizaton of the multi-functional laminate.

Li1.4Al0.4Ti1.6(PO4)3 Used as Solid Electrolyte for Structural Supercapacitors

Structural supercapacitors are very interesting multifunctional devices combining the properties of an electrical energy storage device and a structural component simultaneously. These types of supercapacitors are mostly equipped with solid state electrolytes, instead of traditional liquid electrolytes, avoiding leakage and safety problems and supporting the mechanical performance of the composite materials. In the present study, the Lithium-ion based solid ceramic electrolyte Li1.4Al0.4Ti1.6(PO4)3 was successfully synthesized by sol-gel method. Its electrical properties were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Results show that Li1.4Al0.4Ti1.6(PO4)3 possesses a conductivity of 2.94×10−4 S/cm at room temperature and a specific capacity of 55.57 μF/g. The as-prepared samples were embedded into fiber composite material using the aviation approved resin RTM6 with an injection process making the composite structure flexible. Subsequently, the specific capacity and conductivity were tested getting values of 53.44μF/g and 2.00×10−4 S/cm respectively. The reason for electrical properties loss was investigated by computerized tomography (CT) and EIS tests and the results provide reference for the future research.Copyright

Experimental Determination of Interlaminar Material Properties of Carbon Fiber Composites

Non Crimp Fabric (NCF) provides a low-cost potential and competitive advantages for thick composite structures. In this chapter, a method will be presented to determine the interlaminar failure under combined through-thickness load conditions. Additionally, the in-plane failure behaviour of NCF composite is discussed and analysed. A new test setup, based on the idea of Arcan, determines the material properties. Test results of combined through-thickness loading are presented by in the form of a shear-compression failure curve. The tests are reproducible and reliable. The failure envelope is finally used to verify known failure criteria.

A New Deployable Truss for Gossamer Space Structures

A new deployable mast for realization of large, deployable space structures such as antennas of high arperture, long instrument booms, large solar arrays or solar sails has been developed at the DLR. The triangular truss is based on the use of longerons of composite tapes and shows a signicant increase in mass eciency compared to existing deployable mast concepts. The longerons of thin carbon bre tapes enable realization of large cross-sectional dimensions which leads to a strong insensitivity of critical compression load towards element length. Thereby, in comparison to trusses with longerons of solid rods - the most commonly used type of longerons - higher truss bay length and radius can be achieved for a lower amount of structural mass. This directly contributes to bending stiness and strength. The folding mechanism makes use of the high deformation capability of longerons of tapes in attened state. It is based on a two path folding pattern where the truss is attened rst in cross-direction and reeled up afterwards. This is enabled by the combined use of exible longerons and hinges added to one batten row and ensures high volume eciency. This is especially true for very long masts as the stowage volume mainly depends on the intial reeling radius.

Damage Classification in Aeronautic Structures using Guided Waves

A composite aircraft door surround structure with an integrated SHM network has been manufactured. The structure has been impacted creating realistic damages such as skin delaminations and stringer debondings. The guided wave signal has been acquired using the SHM-network, allowing the subsequent damage identification. The presented work focuses on the classification of different types of damage using a data-driven approach. The method focuses on feature selection and a Support Vector Machine (SVM) algorithm for damage classification. The results show a SVM algorithm capable of distinguishing between three damage types.

Characterization of multifunctional skin-material for morphing leading-edge applications

Former research on morphing droop-nose applications revealed great economical and social ecological advantages in terms of providing gapless surfaces for long areas of laminar flow. Furthermore a droop-nose for laminar flow applications provides a low noise exposing high-lift system at the leading-edge. Various kinematic concepts for the active deployment of such devices are already published but the major challenge is still an open issue: a skin material which meets the compromise of needed stiffness and flexibility. Moreover additional functions have to be added to keep up with standard systems. As a result of several national and European projects the DLR developed a gapless 3D smart droop-nose concept, which was successfully analyzed in a low speed wind tunnel test under relevant loads to prove the functionality and efficiency. The main structure of this concept is made of commercial available glass fiber reinforced plastics (GRFP). This paper presents elementary tests to characterize material lay-ups and their integrity by applying different loads under extreme thermal conditions using aged specimens. On the one hand the presented work is focused on the integrity of material-interfaces and on the other hand the efficiency and feasibility of embedded functions. It can be concluded that different preparations, different adhesives and used materials have their significant influence to the interface stability and mechanical property of the whole lay-up. Especially the laminate design can be optimized due to the e. g. mechanical exploitation of the added systems beyond their main function in order to reduce structural mass.

Noise and Vibration Reduction with Hybrid Electronic Networks and Piezoelectric Transducers

Vibrations are problems encountered at almost every technical application when there are moving parts or fluids included. Upon the need for lightweight structures, especially in aerospace applications or electric mobility, conventional damping concepts are insufficient because of their extra-weight and low performance at low frequencies. Measures for active noise and vibration reduction have the potential to solve the drawbacks of passive systems. However, a limitation of these concepts arises from the need for complex system models for deriving the controllers. This leads to another possibility to reduce vibrations consisting of piezoelectric transducers attached to the structure and connected to hybrid electric networks. Within this paper, the basic principles of shunt damping, two hybrid electric networks circuits for shunted damping and the experimental validation of a damped system will be shown. Finally—as a challenging example—a circular saw blade is equipped with piezoelectric transducers and negative capacitance hybrid electric networks to reduce the vibration and noise amplitude excited by the cutting process.

Combined Prepreg and Resin Infusion Technologies

This chapter presents a novel manufacturing technology for the production of integrated structures made of carbon fiber composite materials. This manufacturing process is able to considerably reduce the production time of large assemblies for primary structural applications. It is based on a combination of the prepreg and the resin infusion technology, both of which are already established in industrial aerospace production. Experimental studies have been carried out to demonstrate the utility of this process. These investigations focused on the characterization of the generated contact zone through the use of two matrix systems as well as its mechanical properties.