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Development of active composite aerofoil for assessment of novel flow control concepts

Koschichow R., Holeczek K., Koschichow D., Rüdiger F., Kostka P., Langkamp A., Fröhlich J., Modler N.

Composites Theory and Practice

2015

R. 15, nr 3

146--151

In this paper, an investigation of the dynamic effects of the low-amplitude, high-frequency excitation of a composite aerofoil by means of integrated actuators on the flow is presented. For this purpose, a well-established elastic NACA 64-418 profile was manufactured from a glass fibre reinforced epoxy resin with integrated active elements. The modal properties of the profile were optimized during the design process in such a way that the spatial distribution of nodes and antinodes of the profile is potentially advantageous for the influence of the flow behaviour around the profile. Additionally, the respective eigenfrequency of the profile should be high enough to efficiently influence the flow. The first numerical and experimental results confirm that the aimed modal properties could be obtained. The optimized profile design has been implemented in the resin transfer moulding manufacturing process and selected low-profile actuating elements were applied after fibre-reinforced plastics consolidation on the inner surface of the NACA profile. The applicability of the proposed flow control approach will be evaluated in detail in a specially developed flow channel in further investigations.

W pracy przedstawiono badania dynamicznego wpływu niskoamplitudowego, wysokoczęstotliwościowego pobudzenia za pomocą zintegrowanych w kompozytowy profil lotniczy elementów wykonawczych na opływające profil medium. W tym celu dobrze poznane profile typu NACA 64-418 zostały wytworzone z materiału kompozytowego na bazie żywicy epoksydowej wzmocnionej włóknami szklanych i wyposażone w zintegrowane elementy wykonawcze. Parametry modalne profili zoptymalizowano w procesie projektowania w taki sposób, iż przestrzenne rozmieszczenie węzłów i strzałek profilu ma potencjalnie korzystny wpływ na opływające go medium. Dodatkowo, odpowiadająca tej postaci częstotliwość własna profilu musi być wystarczająco wysoka, aby efektywnie wpływać na przepływ. Pierwsze numeryczne i eksperymentalne wyniki potwierdzają możliwość uzyskania zamierzonych parametrów modalnych. Do wytworzenia zoptymalizowanej konstrukcji profilu wykorzystano technologię RTM (ang. Resin Transfer Moulding). Po skonsolidowaniu profilu wybrane cienkie elementy wykonawcze zostały zaaplikowane na wewnętrznej powierzchni profilu NACA. Możliwość zastosowania proponowanego podejścia do kontroli przepływu medium będzie określana szczegółowo w dalszych badaniach w specjalnie skonstruowanym kanale przepływowym.

Frequency dependence of the self-heating effect in polymer-based composites

Katunin A., Hufenbach W., Kostka P., Holeczek K.

Journal of Achievements in Materials and Manufacturing Engineering

2010

Vol. 41, nr 1-2

9-15

Purpose: The self-heating effect caused by viscous energy dissipation in polymer-based composite structures subjected to harmonic loads is considered to have a great influence on the residual life of the component. The purpose of the conducted investigations is the determination of the dynamic mechanical behaviour of a polymer-based composite material under different excitation frequencies and temperatures. Design/methodology/approach: The dynamic mechanical analysis was employed for measurements of temperature and frequency dependence of the complex rigidity parameters. Obtained loss rigidity curves for different load frequencies enable the determination of the glass-transition temperatures and finally frequency-dependence of the loss rigidity determined on the basis of the kinetic molecular theory and Williams-Landel-Ferry (WLF) hypothesis. Findings: The dependency between glass-transition temperature and excitation frequency has been investigated. The activation energy of the phase transition as well as the temperature dependence of the shift factor was calculated. The glass-transition temperature and constants of WLF equation enable the determination of temperature and frequency dependence of the loss rigidity according to the time-temperature superposition principle. Research limitations/implications: The ranges of temperatures were limited to 30-150 °C and excitation frequencies to 1-200 Hz, the behaviour of the composite material outside these ranges can be estimated based on the theoretical assumptions only. Obtained dependencies are correct only for linearly viscoelastic materials. Practical implications: Obtained dependencies can be useful for estimation of the mechanical and thermal degradation of polymer-based composites and can be subsequently applied for the determination of fatigue, crack growth and residual life of composite structures. Originality/value: The determination of temperature and frequency dependence of the loss rigidity gives an opportunity to obtain the self-heating temperature distribution of the polymer-based composite structures under harmonic loading.