A STUDY ON THE ELASTIC TAILORING OF A COMPOSITE BOX-BEAM USING CROSS-SECTIONAL GEOMETRY CHANGES

摘要

The present work is a parametric study that examines the impact of varying the geometric cross-section parameters on the structural stiffnesses of an advanced composite box-beam representing a rotor blade spar. Two laminate stiffness configurations/cases have been considered. Case 1 is a box-beam without elastic coupling due to the presence of balanced laminate configuration in all its walls whereas Case 2 is a box-beam with chord-wise bending coupling induced by unbalanced laminate configuration in its vertical walls. Three geometric changes for each case have been considered as variables of study: a) Change in the angle of inclination of a single web of the box-beam, b) Change in the angle of inclination of both webs of the box-beam in opposite directions, and c) Change in the angle of inclination of both webs of the box-beam in the same direction. The impact that these variables have on the elastic tailoring of the box-beam is studied. The variation of the stiffness parameters for the three geometric configurations including the coupling parameters has been visualized into parametric maps. In addition to the study of extensional stiffness, flapwise bending, chordwise bending and torsional stiffnesses of the Euler-Bernoulli stiffness matrix of the box-beam, the behavior of the chordwise bending- torsion coupling has also been studied for Case 2; the twist-bending coupling plays a vital role in determining the dynamic behavior of the blade. The plots of the mass variation as a function of the geometric changes have been generated. The parametric study presented here has potential applications in the target vector optimization of the box-beam in rotor blade lower level optimization.