Aim of the EC sponsored project 'Multidisciplinary Design and Optimization of Blended Wing-Bodies' is the development and application of a fully integrated Computer Design Engine (CDE). TU Delft contributed to the project with the development of a Blended Wing-Body Multi-Model Generator, which is able to supply geometries and data to the analysis software, either COTS or tailor made, used by the various disciplinary groups in the project team (aerodynamics, structures, stability and control etc.). A full parametric definition of the aircraft has been implemented in the KTI ICAD environment. The ICAD Multi-Model Generator (or Generative Model) holds the 'knowledge' of the Blended Wing Body aircraft, such that consistent models can be generated, at different leve ls of fidelity, suitable for the various disciplines involved in the CDE. A large range of aircraft variants can be generated, just editing the values of the aircraft parameters, which are all collected in one single input file. The optimiser can change the parameters value within the optimisation loop, without the need for user interactive sessions. The generative model can be run in batch mode, even from remote sites.
This paper presents the use of a new class of flight control actuators employing Post-Buckled Precompressed (PBP) piezoelectric elements in morphing wing Uninhabited Aerial Vehicles (UAVs). The new actuator relies on axial compression to amplify deflections and control forces simultaneously. Two designs employing morphing wing panels based on PBP actuators were conceived. One design employed PBP actuators in a membrane wing panel over the aft 60% of the chord to impose roll control on a 720mm span subscale UAV. This design relied on a change in curvature of the actuators to control the camber of the airfoil. Axial compression of the actuators was ensured by means of rubber bands and increased end rotation levels with almost a factor of two up to ±13.6• peak-to-peak, with excellent correlation between theory and experiment. Wind tunnel tests quantitatively proved that wing morphing induced roll acceleration levels in excess of 1500 deg/s 2 . A second design employed PBP actuators in a wing panel with significant thickness, relying on a highly compliant Latex skin to allow for shape deformation and at the same time induce an axial force on the actuators. Bench tests showed that due to the axial compression provided by the skin end rotations were increased with more than a factor of two up to ±15.8• peak-to-peak up to a break frequency of 34Hz. Compared to conventional electromechanical servoactuaters, the PBP actuators showed a net reduction in flight control system weight, slop and power consumption for minimal part count. Both morphing wing concepts showed that PBP piezoelectric actuators have significant benefits over conventional actuators and can be successfully applied to induce aircraft control.
To explore the possibilities of a multidisciplinary fuselage design, first the mechanical properties of a stiffened fuselage are discussed. This gives an idea of the available room to vary the structural parameters of such a fuselage. Section 1 describes the design window of a CFRP stiffened fuselage. This design window is created by the possible CFRP fuselage designs (by varying the frame pitch and skin thickness) which are lighter than the lightest aluminium stiffened fuselage.In the remainder of Part III the integration of acoustical insulation in a stiffened shell fuselage is discussed resulting in a design strategy for optimal integration.
The concept of stress is very useful to describe the effect of external loads on structures. However, as a basis for the prediction of failure the concept of stress becomes meaningless when the structure encompasses singularities as a result of discrete stiffness steps or geometric anomalies such as cracks. In this article it is argued that the concept of failure stress is incorrect and should be replaced by a generalized concept based on stress intensity factors and singularity orders. It appears that material failure stress is the critical stress intensity factor for a zero-order singularity stress field. By plotting the critical stress intensity factor as a function of singularity order, the strength of a material can be characterized in a general fashion that integrates tensile strength, fracture toughness and critical singularities in adhesive joints. It is also shown that plasticity does not eliminate the stress singularity in an adhesive joint but changes the order of the singularity due to the induced change in interface corner angle between the dissimilar materials in the joint.
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