Induktive Verklebung von Versteifungsprofilen an gekrümmten Hochleistungsstrukturbauteilen aus CFK

Im Mittelpunkt aktueller Forschungen steht der Einsatz von CFK, das in Zusammenarbeit mit den führenden Flugzeugherstellern für die Luftfahrt entwickelt und erprobt wird. Bereits aktuelle Flugzeugmodelle unterschiedlicher Hersteller haben Strukturbauteile aus CFK (Rumpf- und Flügelschale, Seitenleitwerk, Landeklappe), die durch spezielle Profile versteift werden müssen. Nach aktuellem Stand der Technik werden diese Profile mit gewöhnlichen Heizmethoden zeitaufwendig – ineffizient und somit unwirtschaftlich – vorverklebt. Abschließend kommt das Bauteil mit den vorverklebten Versteifungselementen in den Autoklav, wird dort vollständig verklebt und ausgehärtet. Im Zentrum für Leichtbauproduktionstechnologie (ZLP) des Deutschen Zentrums für Luft- und Raumfahrt e.V. in Stade wurde im Team Infusion- und Aushärtungsprozesse ein neues Verfahren zur Herstellung eines Faserverbundbauelementes patentiert. Das Patent beinhaltet u.a. die Vorverklebung von zwei Teilelementen aus einem Faserverbundwerkstoff durch das Einstrahlen eines elektromagnetischen Wechselfeldes (Induktion). Das führt in mindestens eines der Teilelemente zur Erwärmung des jeweiligen Teilelementes und zur Erwärmung des Klebstoffes

Sensor-assisted monitoring of the production of rotor blades for wind power plants

The detailed monitoring of the production of rotor blades for big wind power plants is becoming increasingly important. This is necessary since rotor blades from the current production are still subject to very great fluctuations in the material and geometry properties. The knowledge of these manufacturing-related deviations is indispensable for an accurate description of the plant's behavior. A valid modeling and optimization with regard to aerodynamics, structural behavior and design can only be carried out with real measured parameters from the production of the existing DFWind research plant

Inductive Pre-Bonding of Stiffened Structural Components Made of CFRP Using the Example of Co- and Secondary Bonding Processes

This paper presents a reliable and patented concept for the effective pre-bonding of stiffened elements on high performance structural parts. In a twofold bonding process, the irradiation of the alternating magnetic field heats the adhesive layer between the CFRP components and pre-bonds them together. The main bonding of the adhesive joint takes place in an autoclave under high temperature and pressure where it completely cures. The focus of this paper is on the pre-bonding process as a result of the enormous opportunities for development. That is based on the time-consuming heating techniques that are used in the current manufacturing process. Performed experiments show that the used concept based on inductive heating can drastically reduce the required time from 20 – 25 seconds per adhesion point to 2.5 – 3 seconds with the same or better pre-bonding quality as with actual state-of-the-art techniques

Berührungslose Wanddickenmessung von Rotorblättern während der Fertigung

Sensorbasierte Fertigung von Rotorblättern zur berührungslosen Dickenmessung der Bauteile während der Fertigung

Impuls Echo – Neue Wege der Industrie 4.0 durch eine ultraschallbasierte In-Line QS im Aushärteprozess

Schon seit Jahren ist das Potential von Faserverbundkunststoffen in der Industrie erkannt worden, was sich vor allem durch die konstanten Wachstumsraten zeigt. Die Herstellung von Bauteilen für die Luftfahrt ist dabei sehr kostenintensiv und unterliegt hohen Qualitätsanforderungen. Es ist also notwendig den Prozess zunehmend zu automatisieren und genaue Kenntnisse über den Zustand eines Bauteils zu detektieren. Nur so kann eine hohe Qualität und dessen Reproduzierbarkeit gewährleistet werden. Dies gilt vor allem für den Aushärtegrad des Bauteils. Dessen Fortschritt lässt sich während des Prozesses nur schwer detektieren. Nach aktuellem Stand der Technik gibt es keine Technologie, die die Detektion und den berührungslosen Einsatz bei „open mould“ Bauteilen, im konventionellen Prozess realisieren kann. In Zusammenarbeit mit Grasse Zur Composite Testing hat das DLR eine ultraschallbasierte Methode entwickelt, um berührungslos, einseitig und bei hohen Temperaturen messen zu können. Dadurch wird es möglich, aktiv in den Aushärteprozess einzugreifen

Auslegung und Validierung eines optischen Sensorsystems zur Wanddickenmessung während der Fertigung von Rotorblättern aus Faserverbund-Materialien

Die vorliegende Arbeit dient zur Erstellung eines Konzepts zur Überprüfung der Laminatdicke während der Fertigung von Rotorblättern für Windkraftanlagen. In diesem Zusammenhang wird die Detektion von glasfaserverstärkten Kunststoffstrukturen berührungslos durch Einsatz optischer Messsysteme erprobt und deren Laminatdicke mittels einer geeigneten Auswertungsmethodik berechnet. Die Erprobung zur Aufnahme eines weiteren fertigungsrelevanten Parameters wird als Ergänzung in die bestehene Messplattform des DLR, zur Forschung an qualitätssichernden Maßnahmen in der Produktion, integriert. Aus den Versuchsreihen geht hervor, dass die Ermittlung der finalen Laminatdicke nach Abschluss des Aushärtungsprozesses durch die Vermessung mit dem Laser - Profilsensor MLWL234, eine Messgenauigkeit von 0,76 mm erreicht werden kann. Die Versuchsreihen zur Ermittlung der zeitabhängigen Laminatdickenänderung während des Infusionsprozesses, ergaben aufgrund starker Lichtreflexionen an den Hilffsstoffen des Vakuumaufbaus, keine brauchbaren Messergebnisse. Aus diesem Grund wurde die Überprüfung der Laminatdickenänderung während der Infusion, in dieser Arbeit nicht näher behandelt

ONLINE INTELLIGENT CURE MONITORING FOR AEROSPACE APPLICATIONS

The constant growth rates in the field of fiber composite materials show a potential that has been rising for years. Fiber composite materials are contributing to this growth. Above all, autoclave and resin transfer molding (RTM) processes for the production of large components and high-volume components for the aerospace industry have become essential in the area of fiber composite construction. Therefore high quality and safety requirements apply to the products produced, as well as a continuous need for economic efficiency improvement for components and processes. The detection of these components and process-relevant information is one of the key points for improving quality and efficiency. An intelligent process monitoring system has been employed for the in-situ monitoring of composite aerospace structure manufacturing. The simultaneous measurement of the resin’s temperature and electrical resistance allows for real-time prediction of viscosity, degree of cure, glass transition temperature (TG) and deviations in mixing ratio. The correlation between electrical resistance, viscosity and degree of cure evolution of widely used aerospace resins proves the accuracy and repeatability for the cure prediction up to the end-of-cure. Due to the different application areas a common ultrasonic system was used. It will discuss how the measurement data of both methods can be correlated and supported

THE WAY TO DECREASE THE CURING TIME BY 50% IN THE MANUFACTURING OF STRUCTURAL COMPONENTS USING THE EXAMPLE OF FML FUSELAGE PANELS

Based on the missing cure monitoring in the manufacturing of structural components, the degree of automation and thus the increase in production cannot be improved. Since much more airplanes per month have to be produced promptly, a higher degree of automation is indispensable. Especially in the field of Fibre Metal Laminates (FML), there is a high potential. The development of a new production line that will allow automated fuselage production is the focus of the studies within the joint project AUTOGLARE. In order to ensure the optimal processing of the reinforced adhesive, a process monitoring system has been developed for the in-situ process monitoring of the manufacturing process within an autoclave. The simultaneous measurement of the resin’s temperature and electrical resistance allows for the real-time prediction of the viscosity, the degree of cure and the glass transition temperature (Tg). The curing of the polymer adhesive was modelled in the lab and its electrical properties were correlated to its T g. Finally, the cure monitoring system was installed in the autoclave and several trials and an entire fuselage were executed. The continuous measurement of the temperature and resistance in all sensors was quite smooth and accurate while the ORS system provided successfully the evolution of the Tg at four critical locations. The present scientific publication shows that the use of a process monitoring system can provide a reliable means to achieve online and accurate T g estimation during the FML manufacturing in an autoclave with a potential to decrease the curing time by 50%

Efficient and sustainable rotor blade manufacture enabled by online quality assurance systems in combination with low-waste resin flow control

Wind turbine blade manufacturers are confronted with increasing challenges regarding quality assurance and recurrent costs in the production of rotor blades which are getting larger and larger with each design cycle. The increasing size of the blades demands for a guaranteed product quality during production due to the high value which is given by the material costs and the effort in form of labor costs which have to be put into the creation of a rotor blade of the newer generations with length of 80 m and more. Quality assurance methods and equipment feasible for rotor blade production are still hard to find today. DLR has developed a method suitable for blade production based on available sensor technologies and has validated it in several production trials in its prototype blade form of 20 m length. The system consists of a mobile optical measuring cell, which is able to check all quality-relevant parameters during blade manufacture. It consists of a thermographic camera which is mounted on a mobile rack and which, in combination with several thermocouples in the mold, enables the measurement of the temperature distribution of the entire component during the curing process. Furthermore, high-resolution cameras, infrared and laser systems are integrated in order to supplement the process monitoring by means of fibre angle detection, leakage detection and construction thickness measurement. With this set of described measurement systems, it is possible to monitor the relevant quality parameters during infusion and curing of rotor blade components. An appropriate computer and software system allows the collection, processing and analysis of the gathered data, which in combination with a database also takes over its documentation. The system enables a more efficient curing process. Furthermore live data analysis can be used to improve the production regarding repeatability and process reliability. It can also be used as a basis for process automation. Post analysis allows for the application of Industry 4.0 approaches, resulting in an increase in process efficiency and a reduction of production defects and rework actions. This approach for online quality assurance can be combined with an active control of the flow front of the resin using the method of temporary usable channels in the vacuum bagging which can be used to control the resin distribution. To realize this effect specific low cost devices are put on top of the vacuum bagging. A separate, controlled vacuum system is used to create the temporary channels in the vacuum bagging and achieve the guided resin flow. It has been proven that these devices leave no detectable channel marks on the surface of the produced product. An additional advantage is the possibility to abstain from the use of distribution media and other auxiliary production material, including the caught and lost resin inside these materials. In addition the specific low cost devices are reusable several times which in summary leads to a significant reduction of the recurrent costs in production. In the presentation the mentioned supporting systems for efficient and sustainable production will be explained and the proofs of its validities will be discussed in detail