Nowadays, weight reduction and efficiency improvement in different parts of airplanes are the most challenging issues of engineering which are being overcome by new approaches like the employment of modern sciences namely smart materials. The research on enhancement of lift coefficient of the aircraft's wing has made it necessary to revise the use of discontinuous flaps. Design, analysis, and the test of a smart morphing airfoil are being studied in this research which is independent of traditional colossal and bulky actuators such as hydraulic jacks and various linkages by using Shape Memory Alloy wires in order to change the camber of airfoil by continuously movement of trailing edge. To this end, flexibility enhancement is evaluated by exploiting an innovative design of a novel composite beam. Flexibility creation in a composite airfoil prototype with an implemented similar design on the beam at the previous step and using shape memory alloy wires on this structure as actuator facilitates the achievement of an applicable smart morphing airfoil. In the end, by modeling and testing investigated structures, this research attempts to answer the question 'Is it possible to anticipate real displacements of the airfoil by simulating smart airfoil structure by finite element analysis?'. The answer is affirmative with 1.31 mm root mean square error between the tail displacement of the simulated model of the airfoil and experimental results.
Dispersion forces such as van der Waals and Casimir interactions become important when the size of structures shrinks. Therefore, the effective design of micro and nano-sized structures depends on appropriate consideration of these forces. In the current research, we analyzed the effect of dispersion forces on the dynamic behavior of a micro/nanobeam actuated by electrostatic forces subject to a mechanical shock. We used the Euler–Bernoulli beam theory including nonlinearities due to mid-plane stretching in our model. The equation of motion is solved using time-dependent finite element method, and pull-in forces are calculated. The stability regimes are evaluated as the set of three force parameters in which the beam elasticity overcomes the external forces, and the beam is able to vibrate without hitting the substrate. Results show that the design of the beam should be such that the three sets of non-dimensional parameters that determine the intensity of shock, dispersion, and electrostatic force do not fall above the stability limit to avoid pull-in instability. Our results have applications in the design of electrostatically actuated micro/nanobeams in mechanical shock environments such as accelerometers.
In this paper, a new flexible sandwich structure is introduced, which can be employed in morphing aircrafts capable of intelligently changing their shape in different flight conditions. To accomplish this goal, first, a review of the various ideas in the literature is presented. In the following, features of the proposed structure and its differences from other ideas are expressed. Then, the process of fabrication and the various stages of shaping the structure are described. In an aircraft with variable wings camber, the deformable section can be assumed to be a cantilever beam. Thus, samples of the proposed structure are fabricated as the cantilever beam and are tested as tip-loaded beams. Since the numerical analysis of the new structure involves the recognition of the mechanical behavior of its components, a comprehensive review of the mechanical behavior of each component of the structure is performed. Afterwards, the numerical method is utilized to model samples of the structure, and the changes in the samples’ deformation are examined under different loads. According to the observation of the broken samples, to arrive at more accurate numerical results, a distribution for the cavities, caused by the manufacturing process, is considered. Finally, with the same assumptions, another sample is analyzed, and it is shown that the results of the second model are consistent with experimental results.
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