Braunschweig, Germany


Braunschweig, Germany
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Klebor M.,HPS GmbH | Hepp F.,HPS GmbH | Pfeiffer E.K.,HPS GmbH | Linke S.,INVENT GmbH | And 2 more authors.
European Space Agency, (Special Publication) ESA SP | Year: 2012

Composite materials used in S/C platforms and payloads can benefit from the latest developments in carbon fibres and nano-technologies. One of the most relevant novelties is the gradual incorporation of nano-species in the resin systems. This paper addresses the results of several technology studies lead and or performed by HPS. They deal with the incorporation of CNT and other nano-species into CFRP to improve the physical properties and to antagonise specific CFRP drawbacks like e.g. the anisotropic properties based on the respective carbon fibre setup. The most interesting and promising applications for these novel composites were assessed and selected for composite development. Entities from several European countries worked together to establish composite and structure processing methods. Promising results concerning electrical and thermal properties were obtained but also many challenges had and still have to be faced. During the projects it has been found that different ingredient combinations and manufacturing processes are favourable for different applications/improvements. It seems that the CNTs and the processes have to be tailored for one specific target property, e.g. electrical conductivity enhancement. The achieved material improvements were and are still further investigated.

Lancelle D.,German Aerospace Center | Bozic O.,German Aerospace Center | Martinez Schramm J.,German Aerospace Center | Linke S.,INVENT GmbH
IEEE Transactions on Plasma Science | Year: 2011

The technology of electromagnetic driven Lorentz rail accelerators (LRAs) has been significantly improved in the last years. Due to the extreme acceleration in LRA systems, there are high demands regarding the mechanical stresses. It is assumed that materials can withstand stresses exceeding the nominal limits related to static conditions if they are applied for a short time. To assess the short-time material strength of a hydroxyl-terminated- polybutadiene rocket fuel grain, experiments shall be carried out using the High-Enthalpy Shock Tunnel Gttingen of the German Aerospace Center in Gttingen as a high-acceleration test facility. In the first step, different samples of the rocket fuel grain and composite materials are tested under high acceleration and analyzed by a visual check. In this paper, first of all, different samples of the rocket fuel grain and composite materials are tested under high acceleration and analyzed by a visual check. In the second step, onboard electronics mounted on the piston are developed to collect the data of the strain and the deformation of the composite/fuel grain and to directly measure the acceleration. With this electronically enhanced specimen, another test is carried out, and measurement data are acquired. The evaluated experiments shall provide useful information to design a hybrid rocket engine for a small launcher, capable to be launched from an LRA. © 2010 IEEE.

Pfeiffer E.K.,HPS GmbH | Reichmann O.,HPS GmbH | Ihle A.,HPS GmbH | Linke S.,INVENT GmbH | And 7 more authors.
Proceedings of the 5th European Conference on Antennas and Propagation, EUCAP 2011 | Year: 2011

In November 2010 the thermo-mechanical test campaign of a Ka-Band multi beam dual reflector antenna structure has been successfully finished. The innovation of this structure lies in the full CFRP sandwich design (including honeycomb core), the use of ultra high modulus fibres for all reflectors, tower panels, base panel, curved cleats, etc.) and in the bonded intersections (e.g. between base panel and tower structure), thus, reducing the in-orbit thermo-elastic distortion to a minimum. In addition, the extremely low mass to high stiffness ratio is unique for European antenna structures. The interfaces to the spacecraft are titanium isostatic mounts compensating a possible CTE mismatch with the spacecraft top deck. The paper presents not only the design and the results of the dynamic test campaign, but also the innovative highly accurate thermo-elastic measurements performed under vacuum conditions using an ESPI measurement system and FBG optical sensors. Parent to the full CFRP antenna structure technology is the development of a new concept of Ku/Ka-Band dual gridded reflector (DGR): the front grid consists for e.g. a 1.2 m reflector of approx. 700 CFRP rods. The rear reflector can either be made of a solid full CFRP reflector shell or out of a second grid, which would lead to a revolutionary low DGR weight. The paper summarizes the results of the developments performed so far, up to the goal of first concepts for shaping the reflector grids, which would enhance significantly the application possibilities. © 2011 EurAAP.

Geier S.,German Aerospace Center | Kintscher M.,German Aerospace Center | Heintze O.,Invent GmbH | Wierach P.,German Aerospace Center | And 2 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

Natural laminar flow is one of the challenging aims of the current aerospace research. Main reasons for the aerodynamic transition from laminar into turbulent flow focusing on the airfoil-structure is the aerodynamic shape and the surface roughness. The Institute of Composite Structures and Adaptive Systems at the German Aerospace Center in Braunschweig works on the optimization of the aerodynamic-loaded structure of future aircrafts in order to increase their efficiency. Providing wing structures suited for natural laminar flow is a step towards this goal. Regarding natural laminar flow, the structural design of the leading edge of a wing is of special interest. An approach for a gap-less leading edge was developed to provide a gap- and step-less high quality surface suited for natural laminar flow and to reduce slat noise. In a national project the first generation of the 3D full scale demonstrator was successfully tested in 2010. The prototype consists of several new technologies, opening up the issue of matching the long and challenging list of airworthiness requirements simultaneously. Therefore the developed composite structure was intensively tested for further modifications according to meet requirements for abrasion, impact and deicing basically. The former presented structure consists completely of glass-fiber-prepreg (GFRP-prepreg). New functions required the addition of a new material-mix, which has to fit into the manufacturing-chain of the composite structure. In addition the hybrid composites have to withstand high loadings, high bending-induced strains (1%) and environmentally influenced aging. Moreover hot-wet cycling tests are carried out for the basic GFRP-structure in order to simulate the long term behavior of the material under extrem conditions. The presented paper shows results of four-points-bending- tests of the most critical section of the morphing leading edge device. Different composite-hybrids are built up and processed. An experimental based trend towards an optimized material design will be shown. © 2012 SPIE.

Benedix W.-S.,TU Dresden | Plettemeier D.,TU Dresden | Zanoni A.,Sudan University of Science and Technology | Preller F.,Invent GmbH | Ciarletti V.,University of Versailles
IEEE International Conference on Wireless for Space and Extreme Environments, WiSEE 2013 - Conference Proceedings | Year: 2013

The Experiment 'Water Ice and Subsurface Deposit Observations on Mars' (WISDOM) is a Ground Penetrating Radar (GPR) selected to be part of the Pasteur payload on board the rover of European Space Agency's (ESA) ExoMars 2018 mission. The GPR antenna system described in this paper is the consequent progression of former developments [1, 2] incorporating changed requirements and further optimizations. Main constraints are the mass, the temperature range as well as the ultra-wide band demand. The antenna requirements which are to fulfill for this very specific GPR application are described here. Furthermore, it is given an overview about the lightweight design and its realization. Simulated and measured antenna performance is compared in this paper. © 2013 IEEE.

Falken A.,INVENT GmbH | Steeger S.,INVENT GmbH | Heintze O.,INVENT GmbH | De Breuker R.,Technical University of Delft
24th AIAA/AHS Adaptive Structures Conference | Year: 2016

The INVENT GmbH rises in the EU project CHANGE under the lead of Tekever and in cooperation with project partners to the challenge to manufacture a gapless and flexible solution for morphing leading and trailing edges of small unmanned aircrafts. Several pretests with thought-provoking material combinations are evaluated previous to the design phase. Solutions for load introduction structures for highly flexible skins for aerodynamic applications are proposed. In parallel to the material design process INVENT produces and tests fibre composites with elastomeric material matrices. As a result a composite with carbon fibre properties parallel to the fibres and elastomer properties perpendicular to the fibres is being developed. Following the production, this material can be combined with epoxy-prepreg in co-curing cycles, an essential demand for both stiff and flexible wing structures. Apart from this, two concepts with conventional fibre composites and two with advanced elastomeric material concepts are designed by the partners Deutsches Zentrum für Luft- und Raumfahrt, Middle Eastern Technical University and Technical University of Delft. Based on calculations conducted with finite elements and CAD-designs by the partners prototypes are built and prepared for a half span wind tunnel test preceding the flight test. In cooperation with the partners a trade-off between structural strength as designed, expected morphing performance and manufacturability has been assessed. Deduced from the wind tunnel test one configuration for the flight test will be chosen. INVENT is in charge of manufacturing the fitted morphing leading and trailing edges for the flight test. In parallel with the preparations of the flight test a skin material test campaign will be conducted at INVENT. The target of the test campaign is a qualitative evaluation of the morphing skin performance regarding cyclic loading and exposure to environmental influences. The influence of defects (manufacturing defects and impacts) on the degradation of the skin material will be tested in specially designed test stands. An auxiliary wing structure will be used to create a realistic surrounding. Amongst others ultrasonic inspection will be used to evaluate the progression of defects in the skin. © 2016, American Institute of Aeronautics and Astronautics Inc, AIAA, All rights reserved.

Schilde C.,TU Braunschweig | Schlomann M.,Invent GmbH | Schlomann M.,TU Braunschweig | Overbeck A.,TU Braunschweig | And 3 more authors.
Journal of Nanostructured Polymers and Nanocomposites | Year: 2015

Carbon nanotubes are a high potential filler material for the enhancement of epoxy resins and other polymers regarding thermal, electrical and mechanical properties. Typically, the carbon nanotube material, the surface functionalization and purification as well as the carbon nanotube content and the polymer properties are identified as significant influencing factor for these properties. Additionally, the processing strategy transferring the carbon nanotubes in the epoxy matrix and their dispersion and stabilization within the matrix is of major importance. The challenge of incorporating carbon nanotubes in polymer matrices is to obtain a certain extend of exfoliation withsimultaneousconsideration of the suspension stability, homogeneous distribution and viscosity for further processing to the cured epoxy composite.This study compares mechanical properties and electric conductivity for duromer based composites obtained from the different common production with results achieved by applying a new process for high loadings. In this new process high filling ratios of exfoliated carbon nanotubes up to 60 wt%, high electric conductivities and excellent mechanical properties are realized. © 2015, Nanofun-Poly. All rights reserved.

Schilde C.,TU Braunschweig | Schlomann M.,Invent GmbH | Overbeck A.,TU Braunschweig | Linke S.,Invent GmbH | Kwade A.,TU Braunschweig
Composites Science and Technology | Year: 2015

Based on their extraordinary mechanical, electrical and thermal properties carbon nanotubes (CNT) are attributed as high potential filler material for polymer matrices. Besides the CNT material and functionalization, the properties of the polymer matrix, stabilization additives as well as the production process have a significant influence on the maximum CNT content and the resultant composite properties. Adapted from a modification of commonly used solvent based approaches a production process for high loaded epoxy based composites is presented in this study. In this process high loadings of up to 80wt% CNTs are embedded in the epoxy composite matrix. The resultant mechanical, electrical and thermal properties are investigated for various CNT types, CNT modification, stabilization and loadings. Moreover, a model for the electric conductivity of CNT reinforced composites above the percolation threshold is presented. This model describes the electric conductivity as a function of the composite structure including CNT content as well as a theoretical value for the number of contacts within such a composite network. © 2015 Elsevier Ltd.

Heimbs S.,Airbus | Schmeer S.,University of Kaiserslautern | Blaurock J.,University of Kaiserslautern | Steeger S.,INVENT GmbH
Composites Part A: Applied Science and Manufacturing | Year: 2013

An experimental test series of mechanically fastened bolted joints with countersunk head in quasi-isotropic carbon/epoxy composite laminates under quasi-static and dynamic loads with velocities up to 10 m/s has been conducted in order to investigate potential strain rate effects on the failure behaviour. The test campaign covered bolt pull-through tests, single lap shear tests with one and two bolts and coach peel tests. Identical test equipment has been used for the whole range of test velocities to avoid influences of different test machines. No rate sensitivity occurred for most test configurations. Only the single lap shear tests with two bolts showed a change of failure mode at the highest test velocity enabling higher energy absorption. © 2013 Elsevier Ltd. All rights reserved.

Dicks A.,Ostwestfalen-Lippe University of Applied Sciences | Lohweg V.,Ostwestfalen-Lippe University of Applied Sciences | Wittke H.,INVENT GmbH | Linke S.,INVENT GmbH
IEEE International Conference on Emerging Technologies and Factory Automation, ETFA | Year: 2015

Due to the material changes of components from metal to plastic or composite materials, the structural health monitoring finds more and more interest in the industrial fields. The reason is that these materials are more vulnerable to damage or impacts which cannot be optically detected. In this contribution we present a method to analyze the structure of plastic components with piezo-electrical sensors and actuators. The components are stimulated by actuators, and sensors capture the injected vibrations. These signals are decomposed into Intrinsic Mode Functions to compute statistical features. A Fuzzy-Pattern-Classifier is applied to detect structural modifications at the components under test. © 2015 IEEE.

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