Michael Sinapius

Experimental Investigation of VHCF of Polymer Composites: Two Alternative Approaches*

Abstract The need for reliable fatigue predictions arises with an increasing application of fibre-reinforced composites in primary light-weight structures with intended service times of up to 30 years. Only few data about very high cycle fatigue (VHCF) of polymer composites are available, because VHCF testing is rather challenging due to time consuming tests. Moreover, problems arise when testing at high frequencies. Two alternative approaches are presented in this article, a bending test rig for high-frequency testing of flat specimens and a resonant test rig for tube specimens.

Active Flow Control via Piezo-Actuated Airfoils forHigh-Lift

This paper presents the development process of a dynamically actuated lip for active blowing at high-lift flaps. The system consists of MEMS pressure sensors to determine the flow conditions and adaptive lips to regulate the mass flow and the velocity of a wall near stream over the internally blown Coanda flap. By the oscillating lip the mass flow in the blowing slot changes dynamically, consequently the momentum exchange of the boundary layer over a high lift flap required mass flow can be reduced. In a first functional demonstrator piezo ceramic d33-stack actuators, operating at low voltage levels, are bonded to a metal substrate in a bending transducer configuration for basic experiments to determine the nominal displacement and the blocking force of the adaptive lip. Prospective all control systems shall be coupled to large-area sensor-actuator-arrays and integrated conformable into the structure. The efficiency increase of an internally blown Coanda flap by using unsteady blowing will be investigated during water channel tests which are in preparation. In this context an appropriate waterproof electrical insulation is evaluated by environmental tests. The first flow investigations will be implemented in a water tunnel in order to reduce the flow velocity and the system’s control frequency by a factor of 10 compared to a wind tunnel. Compared to the prior art, an expansion of the frequency range is expected and the benefits due to the compact and highly integrated design demand a high aerodynamic efficiency of this configuration.