An investigation regarding de-icing of wing leading edges through the use of smart structures is performed. Piezoelectric actuators are used to excite the structures at their natural frequencies. This vibration excites shear stresses at the surface, which lead to the shedding off of ice. For optimal excitation of the structure, the frequency and the placement of piezo elements are determined, in order to maximize the shear stress. First, experimental investigations on a clamped aluminum plate are carried out. With these findings, the transition to an aluminum sample of a wing leading edge is performed. Practical experiments have been carried out on a sample of an aluminum wing leading edge. First, the structural behavior is determined by a modal analysis so that the natural frequencies and the eigenmodes can be calculated. By FE simulation all parameter combinations can be calculated, so the practical tests can be adapted accordingly. Practical experiments have been carried out under realistic conditions in terms of ice formation in an icing research tunnel. Different types of ice have been considered, which require a different level of shear stresses for the de-icing. Further investigations will concern the determination of the suitable frequency and furthermore an ongoing monitoring of the process to take up account on different icing conditions. The studies point to a further possibility of energy efficient de-icing.

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Feministische Standpunktepistemologien sind aus der feministischen Wissenschaftskritik am Androzentrismus in der Wissenschaft heraus entstanden. Vertreterinnen der feministischen Standpunktepistemologie diskutieren dabei Fragen nach dem wissenschaftsproduzierenden Subjekt und den Bedingungen der Wissenschaftsproduktion. Insbesondere das Verhältnis zwischen sozialer Positioniertheit – qua Geburt und Sozialisation – und der Einnahme einer epistemisch-politischen Positionierung auf Seiten der Marginalisierten steht im Mittelpunkt dieser Debatten. Wenn neues und differenziertes Wissen auch von privilegierten Positionen aus produziert werden kann, können dann Männer feministisches Wissen produzieren? Unter welchen Bedingungen ist dies möglich und welche Rolle spielt dabei die Institution Universität? Diese Fragen bearbeiten wir mit Blick auf die Figur des feministischen Wissenschaftlers, der zwar feministische Theorie rezipiert, jedoch neben seinem 15-stündigen Arbeitstag keine Zeit mehr für Reproduktionsarbeit hat. Wir schlagen daher eine profeministische Perspektive vor, die über das Individuum hinausgeht und letztlich auf eine profeministische Politisierung der Universität abzielt. Dabei greifen wir auf das Konzept der Hegemonieselbstkritik zurück und schlagen in Anknüpfung daran profeministische Praxen auf vier unterschiedlichen Ebenen vor, die in der Universität erprobt und theoretisch vertieft werden können.

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This contribution deals with the implementation of a PC-controlled structural health monitoring system for continuous damage detection. The system is implemented in a real size demonstrator component made of carbon fiber reinforced polymer (CFRP). The component is equipped with an actuator array of piezoelectric patches which are driven by power amplifiers. With the appropriate test signals elastic Lamb waves are emitted into the continuum in a specific direction. Vibrometer measurements of reflections which are caused by delaminations make it possible to observe the size and position of the defect areas. MOTIVATIONThe utilization of composite materials in modern aircraft design is of growing importance. The main advantages of carbon fiber reinforced polymer (CFRP) compared to metal and metal alloys are the low density, the extended fatigue behavior, the insensitivity to corrosion and the low damage tolerance in general. The weight saving potential by replacing aluminum body parts of an aircraft by CFRP is considerable high and is exploited for reducing the fuel consumption and therefore the overall operational costs.The weaknesses of CFRP material include an impractical plasticity and high sensitivity to impacts, which may cause delamination. Furthermore, repairing of partial damage and recycling of rejected parts, if at all technically feasible, require high effort. Impact caused delamination may result in a reduced stability of the CFRP structure and thus demands thorough inspection of structure parts at risk. Inspection can be conducted visually by an experienced person or by nondestructive testing methods like ultrasound scanning. The disadvantage of both practices is the high consumption of resources and time. Moreover, they can only be conducted on ground and contribute to the inoperable time of an aircraft.With novel methods of structural health monitoring (SHM) these problems could be solved by providing measurement methods which allow easy access and short test intervals for the inspection of complex materials. SHM makes a continuous monitoring of structures possible with a sensor system which is applied to the structure itself. Thus a nondestructive testing procedure can be executed automatically and as many times as necessary. The goal is to identify possible failures and damages at once, and, even more important, to get information before a breakdown of a specific component is even occurs. Benefits of SHM systems include the reduction of maintenance resources, the reduction of machine down times, an active increase of the product lifetime, and the improvement of safety. [1] In chapter 2 of this contribution an overview of SHM with guided Lamb waves is presented in chapter 2. Our PCcontrolled phased array system and its electronics components are described and evaluated in chapter 3. In chapter 4 the results of Vibrometer measurements of directed Lamb waves and their interaction with delaminations on CFRP specimen are discussed. Finally, a summary and an outlook to future work are given in chapter 5. ...