The active twist control of helicopter rotor blades by an application of macro-fiber composite (MFC) actuators leads to significant vibration and noise reduction without the need for complex mechanisms in the rotating systems. For environmental improvement an optimal design methodology based on planning experiments and response surface technique has been developed for an active twist of helicopter rotor blades consisting of C-spar made of unidirectional GFRP, skin made of +45°/−45° GFRP, foam core, MFC actuators embedded into the skin and balance weight. The structural static analysis with thermal load, static torsion analysis and modal analysis using 3D finite element models has been developed using ANSYS for the optimal design. In this case thermal strain analogy between piezoelectric strains and thermally induced strains is used to model piezoelectric effects. The optimization results have been obtained for four design solutions connected with the application of active materials.

The present investigation is devoted to the development of a new optimal design of lateral wing upper covers made of advanced composite materials, with special emphasis on closer conformity of the developed finite element analysis and operational requirements for aircraft wing panels. In the first stage, 24 weight optimization problems based on linear buckling analysis were solved for the laminated composite panels with three types of stiffener, two stiffener pitches and four load levels, taking into account manufacturing, reparability and damage tolerance requirements. In the second stage, a composite panel with the best weight/design performance from the previous study was verified by nonlinear buckling analysis and optimization to investigate the effect of shear and fuel pressure on the performance of stiffened panels, and their behaviour under skin post-buckling. Three rib-bay laminated composite panels with T-, I- and HAT-stiffeners were modelled with ANSYS, NASTRAN and ABAQUS finite element codes to study their buckling behaviour as a function of skin and stiffener lay-ups, stiffener height, stiffener top and root width. Owing to the large dimension of numerical problems to be solved, an optimization methodology was developed employing the method of experimental design and response surface technique. Optimal results obtained in terms of cross-sectional areas were verified successfully using ANSYS and ABAQUS shared-node models and a NASTRAN rigid-linked model, and were used later to estimate the weight of the Advanced Low Cost Aircraft Structures (ALCAS) lateral wing upper cover.