This publication presents the results of complex parametrical strength investigations of typical wings for regional aircrafts obtained by means of the new version of the four-level algorithm (FLA) with the modified module responsible for the analysis of aerodynamic loading. This version of FLA, as well as a base one, is focused on significant decreasing time and labor input of a complex strength analysis of airframes by using simultaneously different principles of decomposition. The base version includes four-level decomposition of airframe and decomposition of strength tasks. The new one realizes additional decomposition of alternative variants of load cases during the process of determination of critical load cases. Such an algorithm is very suitable for strength analysis and designing airframes of regional aircrafts having a wide range of aerodynamic concepts. Results of validation of the new version of FLA for a high-aspect-ratio wing obtained in this work confirmed high performance of the algorithm in decreasing time and labor input of strength analysis of airframes at the preliminary stages of designing. During parametrical design investigation, some interesting results for strut-braced wings having high aspect ratios were obtained.
Results of parametrical investigations of residual strength and buckling of damaged composite panels of civil aircrafts were considered. The investigations were performed on the base of the semi-empirical method developed by the author. The algorithm allows users to carry out the analysis of parameters of stress-strain state and to assess a general buckling behavior of composite panels in the automatic mode. The calculations were performed by using the special parametrical finite element models of composite panels that are typical for current civil aircrafts. The special models of panels consisted of composite laminated skin and different types of stiffeners have zones with reduced stiffness characteristics. The relationship between level of reducing mechanical characteristics of “damaged” zones and residual strength and buckling margins of the panels was determined.
The paper is devoted to the creation of automated methods for calculating the strength of composite structures, taking into account the influence of impact damage and temperature effects in the range from -600 to +600. To solve this problem, a program for automated finite element modelling of a typical reinforced composite panel was created. Program allows to conduct parametric studies of strength and stability in an automatic mode, to model panel impact damage and to parameterize the temperature dependence of the strength of a composite. Using this method, results were obtained on the strength and stability of the panel in the temperature range and in various damage parameters.
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