Design Tailoring for Pressure Pillowing Using Tow-Placed Steered Fibers

Abstract

Manufacturing of high-quality fiber-reinforced composite structures with spatially varying fiber orientation is possible using advanced tow-placement machines. Changing the fiber-orientation angle within a layer produces variable-stiffness properties. Contrary to traditional composites with straight fibers, this method allows the designer to fully benefit from the directional material properties of the composite to improve laminate performance by determining optimal fiber paths. In this paper, design tailoring for the pressure-pillowing problem of a fuselage skin is addressed using steered fibers. The problem is modeled as a two-dimensional plate using von Karman plate equations. The analysis is performed using the Rayleigh-Ritz method, and the nonlinear response is traced using a normal flow algorithm. The design objective is to determine the optimal fiber paths over the panel for maximum failure load. Different designs are obtained for different loading cases. The results indicate that by using steered fibers, the pressure-pillowing problem can be alleviated and the load-carrying capacity of the structure can be improved, compared with designs using straight fibers.