This study proposes a comparison between three identification methods of the mechanical properties of a shape memory polymer (Veriflex ®): quasistatic tensile tests, tensile dynamic mechanical analysis (DMA) and modal tests. The Young's modulus and the Poisson's ratio are determined at ambient temperature using the first technique. The DMA is used to determine the evolution of the viscoelastic properties versus the temperature and the frequency under harmonic loading. The modal analysis is used to identify the viscoelastic properties of the material at higher frequencies. The purpose of this study is to check the validity of the time-temperature equivalence for the Veriflex ® obtained from the DMA measurements. It is shown that the viscoelastic properties predicted through the master curve are consistent with the measurements collected using quasi-static and modal test. The aging effect on SMP properties is also quantified.

Abstract. Shape memory polymers (SMPs) are materials with a great potential for future use in smart materials and structures. When heated from cold state (below the transformation temperature, which can either be the glass transition temperature or the melting temperature of the polymer) to hot state (above the transformation temperature) they undergo transformation which can be compared with martensitic transformation of shape memory alloys. This process induces great changes of the mechanical properties and some shape memory phenomenon can be observed. This study is an experimental evaluation of the mechanical properties of SMP Veriflex ® under different test conditions. Veriflex ® was chosen because of its easy accessibility. Furthermore its properties are similar to epoxy resins which make it very suitable for usage in a wide variety of technical applications. Dynamic mechanical analysis (DMA) was used to determine evolution of the viscoelastic properties versus temperature and frequency under cyclic harmonic loading. The glass transition temperature clearly appears in a range from 45°C to 60°C depending on loading frequency. The glass transition is noticeably marked by an impressive decrease in the storage modulus of about 4 decades. The master curve of Veriflex ® was created and allows the time-temperature superposition to be constructed for this material. Thermo-mechanical working cycle of SMP with 100% elongation was also experimentally tested. Finally results from all these experimental investigations were used to design a demonstrator showing the possibility of application in engineering and especially for shape control.

In this paper a computational methodology of aerodynamic interaction between propeller and wing is described. Presented work is focused on development of quick and accurate tool. Lifting line theory (LLT) with nonlinear airfoil characteristic is used to solve a finite span wing aerodynamic to predict downwash and lift distribution respectively. Blade element momentum theory (BEM) is used as a computational tool for estimating total thrust, torque, axial and tangential velocity distributions. Model of slipstream development is considered. Influence of propeller model to wing is simulated as contribution of higher dynamic pressure and change of angle of attack behind the propeller.

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In this paper, a small airplane is redesigned by using a distributed electrical propulsion (DEP) system. The design procedure is focused on the reduction of fuel consumption in cruise regime with constrained parameters of take-off/landing. In this case, a one half wing area compared to an original airplane is used. Take-off distance and minimum airspeed for landing is achieved by distributed propellers mounted on the leading edge of the wing. These propellers induce velocity on the wing and thereby increase local dynamic pressure, thus the required lift force can be reached with smaller wing area. Moreover, the distributed propellers are assumed as folded in cruise regime to minimize drag when the main combustion engine provides sufficient power.

Selection process of the propeller for short take-off and landing (STOL) category aircraft is described. The aim is to achieve the highest possible performance with fixed propeller, i.e., high maximal horizontal and cruise speed, short take-off and high rate of climb. These requirements are contradictory and so Pareto sets were used in order to find the optimal propeller. The method is applied to a family of geometrically similar propellers that are suitable for 73.5 kW (100 hp) piston engine designed for ultralight category aircraft with maximal take-off weight of 472.5 kg. The propellers have from two to eight blades, blade angle settings from 15° to 40° and diameter from 1.1 m to 2.65 m. Pareto frontier is designed for each pair of flight conditions, and the optimal propeller is selected according to these results. For comparison, the optimal propeller selection from the propeller family by means of a standard single-optimal process based on the speed power coefficient cs is also used. Use of Pareto sets leads to considerable performance increase for the set of contradictory requirements. Therefore, high performance for a low price for the given aircraft can be achieved. The described method can be used for propeller optimization in similar cases.

Paper describes the effect of the distributed electric propulsion system (DEP) on the aerodynamic characteristics of the airplane wing. Using CFD simulation is described the influence of the wake of the propeller on the wing for various ratios of the propeller diameter to the wing chord. Unlike the normal case of wing-propeller interaction, periodic boundary conditions are used, i.e. a rectangular wing with infinite span with propellers installed periodically its span is considered. A wind tunnel experiment will be used to verify the calculations. Propeller thrust is set to compensate for airplane drag in horizontal flight, i.e. equal to the wing segment drag, which is increased by the corresponding part of the expected drag of other parts of the airplane. The increase of the drag was determined by the aerodynamic design of a generic airplane with DEP. The benefit of the work are the input data usable for the conceptual design of the airplane wing with DEP.