Abstract
Thin-walled composite box beam structural configuration is representative of a specific high aspect ratio wing structure. The optimal design procedure and lay-up definition including appropriate coupling necessary for aerospace applications has been identified by means of “ad hoc” analytical formulation and by application of commercial code. The overall equivalent bending, torsional and coupled stiffness are derived and the accuracy of the simplified beam model is demonstrated by the application of Altair Optistruct. A simple case of a coupled cantilevered beam with load at one end is introduced to demonstrate that stiffness and torsion angle distribution does not always correspond to the trends that one would intuitively expect. The maximum of torsional stiffness is not obtained with fibers arranged at 45° and, at the maximum torsional stiffness, there is no minimum rotation angle. This observation becomes essential in any design process of composite structures where the constraints impose structural couplings. Furthermore, the presented theory is also extended to cases in which it is necessary to include composite/stiffened hybrid configurations. Good agreement has been found between the theoretical simplified beam model and numerical analysis. Finally, the selected composite configuration was compared to an experimental test case. The numerical and experimental validation is presented and discussed. A good correlation was found confirming the validity of the overall optimization for the optimal lay-up selection and structural configuration.
Highlights
IntroductionThe introduction of future configurations of unconventional aircraft demand for innovative structural concepts to improve the structural performance, and reduce the structural weight
The introduction of future configurations of unconventional aircraft demand for innovative structural concepts to improve the structural performance, and reduce the structural weight.New materials and specific couplings are necessary to cope with such demanding structural design influencing static and dynamic aircraft performances
The present paper aims to validate theorientations outcomes ofconsidering a low fidelity beam-wise model previously the standardization of the thicknesses and manufacturing and commercial developed and analyze design aspects not clearly highlighted by the available literature in the constraints
Summary
The introduction of future configurations of unconventional aircraft demand for innovative structural concepts to improve the structural performance, and reduce the structural weight. The [C] matrix in Equation (6) is representative of the membrane contribution and local plate stiffness effect as in [8] Specific relations, such as those that represent bending torsion coupled configurations (Circumferentially Asymmetric Stiffness (CAS) models) and stiffness coefficients are computed as in Table 1 where the area enclosed by the midline of the contour section is reported. Numerical optimization is performed to identify the laminate plies angles in order to obtain the most bending-torsion couple effect. The model presented in this work has the composite plates modeled with shell elements that have opposite normal vectors between upper and lower plate, Figure 4b This condition in order to have a visual simplified post-processing of plies angles during the iterative process: the same ply in the upper plate and lower to have the same orientation should be a positive angle value in the upper plate and the same but negative in the lower.
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