Scipedia: II European Conference On Multifunctional Structures (EMuS2020), November, 17-18, 2020

A Technology to (re-)Connect Optical Fibres Embedded in Composite Structures

Scipedia content — Tue, 16 Feb 2021 09:26:37 +0100

Optical fibre Bragg grating (FBG) sensors are commonly used for structural health monitoring in composite materials, since their small dimensions, high sensitivity and multiplexing capacity are a good match with the structures to be monitored. We present a method for making a low-loss connection to an FBG optical fibre sensor that is integrated in a fibre reinforced composite structure. The method allows to both manufacture composite structure without taking special precautions to prevent damage to the connecting fibre and (if needed) to repair the connecting fibre, while optimizing the optical connection efficiency even if both fibres have dissimilar mode field diameters.

Development of a Numerical Framework for Virtual Testing to Support Design of a Next Generation Thermoplastic Multifunctional Fuselage

Scipedia content — Tue, 16 Feb 2021 09:23:25 +0100

This work summarizes the recent developments of a numerical framework to predict the mechanical behaviour of thermoplastic composites. It supports the design of a next generation thermoplastic multi-functional fuselage which uses advanced joining techniques such as thermoplastic welding to reduce both weight and cost by limiting the amount of mechanical fasteners required. At the lower end of the testing pyramid the framework is able to accurately predict typical preliminary design allowables such as laminate, open-hole and welded joints strength through a high-fidelity modelling approach. This information is then passed on to the structural level in a validated building-block approach to efficiently virtual test the compression strength of fuselage panels during post-buckling while also taking into account the influence of damages at the skin-stiffener interface.

Experimental Analysis of the ACASIAS Active Lining Panel

Scipedia content — Tue, 16 Feb 2021 09:25:12 +0100

The participants of the EU-project ACASIAS develop advanced concepts for aerostructures with multifunctional capabilities. Within work package 3 an active system for noise reduction is integrated into a curved lining panel. The objective is the reduction of the interior sound pressure level by increasing the transmission loss of the lining panel. The application scope includes current propeller driven aircraft and future aircraft with counter-rotating open rotor (CROR) engines. The drawback of these CO₂-efficient engines is their high sound emission in the frequency band up to 500 Hz. Active noise reduction systems are able to achieve performance in this frequency band while passive sound insulation materials fall behind. Thus, active systems are the key technology to avoid unacceptably high noise levels for passengers. During the last period of the project the main experiments are conducted. The active lining with its dimensions of 1300 × 1690 mm² (W × H) is mounted in a setup in the acoustic transmission loss test facility of the DLR. Several tests in different categories are run to characterize the vibration and sound transmission behavior of the lining. In this paper the active lining and its components are briefly introduced and the results of the modal and the thermal testing are presented.

GNSS Antenna Integrated into a Classical Fibre Metal Laminate Fuselage Panel

Scipedia content — Tue, 16 Feb 2021 09:22:01 +0100

Fibre Metal Laminate materials, like Glass Laminate Aluminum Reinforced Epoxy (GLARE), provide a unique opportunity to integrate patch antennas directly into the fuselage of aircraft. This integration will contribute to the reduction of carbon emissions of aircraft due to the reduction of aerodynamic drag. This paper discusses the integration of a double patch GNSS antenna directly into a classical Fiber Metal Laminate. A demonstrator of the antenna was manufactured and measured. The antenna has a flush finish on the outside of the fuselage. The preliminary results of these measurements show promising antenna performance, but more measurements are required to fully characterize this integrated antenna.

Influence of the Angle between Adherends on Ultrasonic Welding of Thermoplastic Composites

Scipedia content — Tue, 16 Feb 2021 09:24:14 +0100

Research on ultrasonic welding of composites has focused mostly on studying parameters that are inputs for the process or material-related parameters, but almost no attention has been given on the effect of manufacturing tolerances. In this work, we investigated how an angle between adherends impacts the welding process and the weld quality. By increasing the angle between top and bottom adherends, it was found that the duration of the process increased while the power consumed, the weld uniformity and the weld strength decreased. However, by increasing the clamping distance, which increased the compliance of the adherends and hence their ability to deform under the applied welding force, the effect of the misalignment on both the welding process and weld quality could be substantially reduced.

Multifunctional Fuselage Demonstrator: Thermoplastic Composite Skin Manufacturing Developments

Scipedia content — Tue, 16 Feb 2021 09:26:13 +0100

Within Clean Sky 2 the design and manufacturing of the fuselage of new single aisle aircraft is investigated through a large, multi-functional fuselage demonstrator, see Figure 1. The main objectives of this demonstrator are to enable high production rates with a minimum of 60 aircraft per month and to reduce structural weight and recurring cost. The envisaged demonstrator shall validate high potential multi-functional combinations of airframe structures, systems, cargo and cabin technology concepts for the next generation fuselage and cabin, using advanced materials and innovative design principles. One of the key innovations for the multi-functional fuselage demonstrator is the modular assembly of pre-equipped sub-assemblies, see reference [1] and [4]. To make a step in the design and manufacturing of such integrated multi-disciplinary fuselage sub-assemblies, including components of structures, systems, cabin and cargo, advanced materials and manufacturing methods are required. Thermoplastic composites and their highly automated fibre placement production techniques and advanced joining methods, offer the flexibility and efficiency that is needed for the production of much more pre-equipped sub-assemblies to enable the modular assembly process for the future aircraft production supply chain.

Noise Reduction Results of the ACASIAS Active Lining Panel

Scipedia content — Tue, 16 Feb 2021 09:24:50 +0100

Advanced concepts for aero-structures with multifunctional capabilities are investigated within the EU-project ACASIAS. In work package 3 of ACASIAS, components of an active noise reduction system are structurally integrated into a curved sandwich panel by means of 3D printed inserts. This so-called smart lining is intended for application in aircraft as a modular and lightweight interior noise treatment in propeller-driven aircraft. The broad application scenario of smart linings ranges from retro-fitting of current regional aircraft such as ATR 42, ATR 72, DHC-8 Q400 to the application in new short-range aircraft with energy efficient counter rotating open rotor (CROR) engines or with distributed electric propellers. A key feature of the smart lining with integrated active components is its modularity, facilitating a flexible application in the aircraft cabin. This requires a fully self-contained sensing mechanism based on structurally integrated accelerometers. Using the normal surface vibration data from the integrated sensors, the smart lining is able to predict the sound field in front of it. The so-called virtual microphone method with remote sensors and observer filter allows to get rid of real microphones and wiring in the aircraft cabin. This makes retro-fitting easier because it reduces wiring effort and costs which is beneficial for future aircraft as well. However, the use of virtual instead of real microphones might deteriorate the performance or even the stability of the active noise reduction system because it relies on accurate plant models. Laboratory experiments in a sound transmission loss facility are conducted to assess the behavior of the smart lining with virtual microphones and compare it to a smart lining with real microphones. The sensitivity of the smart lining to environmental changes and the noise reduction performance and control system stability are investigated in this study.

RF Analyses of Integrated Ku-band Antenna

Scipedia content — Tue, 16 Feb 2021 09:15:36 +0100

In the ACASIAS project an integrated antenna for Ku-band satellite communication has been developed. The design of this integrated antenna has to meet structural, electromagnetic and thermal requirements. This paper addresses the electromagnetic performance of the antenna both by design and by measurement. For the design of the antenna, the electromagnetic interaction of the antenna with the conducting Carbon Fibre Reinforced Plastic (CFRP) ribs of the orthogrid and the interaction with the Glass Fibre Reinforced Plastic (GFRP) skin of the panel have been analysed. In addition, the influence of potential lightning diverters on the antenna performance has been analysed. The radiation pattern of a single antenna tile and the radiation pattern of an antenna tile integrated in the orthogrid fuselage panel were measured. The results of the antenna measurements are compared with the results of the simulations carried out for the design of the antenna.

Structural Analyses of GLARE-GFRP Transition for Integrated VHF Antenna on a Fuselage Panel

Scipedia content — Tue, 16 Feb 2021 09:01:29 +0100

The objective of this paper is to describe the numerical simulation of the transition zones in the multifunctional fuselage panel design to integrate a VHF (Very High Frequency) antenna. The panel is made of GLARE (Glass Laminate Aluminium Reinforced Epoxy) with a central window of GFRP (Glass Fibre Reinforced Polymer). The structural analyses of the transition GLARE/GFRP is presented along with its experimental validation. The numerical simulations showed a very high level of correlation with the experimental tests, both in the longitudinal load vs displacement curves and deformations captured with strain gauges and DIC (Digital Image Correlations).

Structural Assessment of FML Aerostructures with Integrated Electromagnetic Features

Scipedia content — Tue, 16 Feb 2021 09:25:50 +0100

A substantial contribution to reduce the aerodynamic drag and consequent CO₂ and NO_x emissions is to integrate communication antennas in the aircraft structure. This paper presents a GLARE fuselage panel design for an integrated VHF slot antenna and discusses the results of a mechanical experimental campaign on a structural element level, in quasi-static tensile conditions. The tested specimens showed small variability in terms of stiffness and strength (typical for GLARE), little dependence on the ambient conditions, damage presence, and layup configurations and good agreement with early numerical simulations. In addition, stiffness and strength predictions, based on empirically found design values seem to correlate well with the found test values

System Development of Transmitting Conformal SATCOM Array Antenna Structures(CSAAS)

Scipedia content — Tue, 16 Feb 2021 09:24:32 +0100

This study presents the development results of Conformal SATCOM Array Antenna Structure(CSAAS) for transmitting. Tile Type antenna with 8x8 antenna element array has been developed instead of reflector antenna. 8x8 tile antennas are arrayed on the curved surface with one directional curvature to simulate aircraft skin configuration. Housing has the grid structure to minimize out-of-plane deformation that affects the antenna performances. Tile antennas are attached to the surfaces between grids. Radome is designed as an A-sandwich type to carry some distributed skin load and glass epoxy material with lowest dielectric constant and loss tangent was used for the best electromagnetic performance. One tile antenna is designed with a separate data control and power connection for vertical and horizontal polarization. The static structural strength of the housing and impact strength of the radome were verified by the analysis and tests. Beam pattern test, beam control test and beam steering test are performed in an anechoic chamber for the transmitting CSAAS. The results of structural and electromagnetic tests showed that the design objects met the goal successfully.

VHF Antenna Integrated into a Classical Fibre Metal Laminate Fuselage Panel

Scipedia content — Thu, 11 Feb 2021 09:46:02 +0100

Replacement of protruding antennas by integrated alternatives will reduce the energy consumption and NO_x and CO₂ emissions of an aircraft. This paper proposes and integrated VHF cavity backed slot antenna that is suitable to replace blade antennas. To reduce the size of the cavity a parallel plate resonator is used. The slot is integrated into a fibre metal laminate fuselage panel. A bookleafing principle is used to reinforce the panel at the position of the slot, making sure the material quality is not reduced. Measurement results of a demonstrator antenna show the feasibility of the proposed antenna. Moreover, the paper discusses several electromagnetic and structural design trade-offs for this integrated antenna.

VHF Communication Antenna Integrated into an Aircraft Winglet

Scipedia content — Tue, 16 Feb 2021 09:25:34 +0100

The article is discussing the final design of a VHF communication antenna integrated in a composite winglet of the EV-55 small transport aircraft. The antenna is designed to operate in the VHF band reserved for civil aviation, 117.975 – 137 MHz with optimal VSWR below 2.5. Compared with a standard vertically polarized monopole antenna, the radiation pattern in the horizontal plane shall not be down more than 6 dB and vary more than 6 dB [2].