Numerical/Experimental Validation of Thin-Walled Composite Box Beam Optimal Design

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.

Experimental and Numerical Dynamic Behavior of Bending-Torsion Coupled Box-Beam

“…The second beam (Fig. 2) presents a similar configuration already considered by Cestino et al [17] for static analyses, based on carbon fiber reinforced polymer (CFRP) with unidirectional (UD) T700 carbon/epoxy prepreg with fibers oriented at 18 • ([18/18/18/18]), for the upper and lower plates 1 mm thick. The design criterium was the same as the previous configuration related to obtain a bending-torsion coupling effect.…”

Bending Behavior Analysis of Box Beams with the Reinforcement of Composite Materials for Wind Turbine Blades

“…However, the structural designs of the WTB and their manufacture are complex, because the folds (creases) that occur after their manufacture can significantly reduce the overall performance of the structure [19]. In addition, research has been carried out to identify the optimal angle of the laminate to perform the stacking sequence of each sheet to form the laminate of a thin-walled beam; subsequently, the thicknesses and orientations of the laminate are optimized to obtain the maximum bending-twisting torque effect [20]. In addition, the damage detection technique using deformation sensors helps to determine the location of the failures, deformations, and stresses produced in the WTB and the beam [21].…”