Buckling Analysis and Optimization of Stiffened Varying-Angle- Tow Laminates with Manufacturing Constraints

Abstract

The variable-angle-tow (VAT) fiber path laminates are known to shift the maximum in-plane stress resultants away from the composite laminated panel’s center to the panel’s supported edges for improving the buckling response when compared to the traditional laminates. However, the improvement in the structural performance could be counteracted due to the fiber placement head turning radius and gaps/overlaps induced thickness variation in the VAT manufacturing process. The present paper investigates the effect of the minimal turning radius on the buckling load of a stiffened VAT laminated plate subjected to an axial in-plane end-shortening. Different laminate fiber path angles are parameterized and studied. Optimization studies show that when there is no manufacturing constraint, there is a significant increase in the buckling load, up to 20.5% and 44.0%, respectively, by using the stiffened VAT laminates with linearly and nonlinearly varying fiber path angles. The optimal linearly- and nonlinearly-varying fiber paths are found to be almost perpendicular to the stiffeners in the panel’s center and almost be parallel to the stiffeners near the panel’s free-load support edges. The present minimal fiber placement head turning radius has a significant effect on the buckling load improvement for the stiffened VAT laminated plates. There are only 6% and 7% increases in the total buckling load for the present stiffened composite plates with linearly- and nonlinearly-varying fiber path angles laminates, respectively, when considering the fiber curvature constraint.