Using Optimization to Improve the Quasi-Isotropic Status Quo

Abstract

Anisotropy of composite materials is both a strength and a weakness. On the one hand, the extreme strength and stiffness provided by carbon fibers is often utilized in uniaxial loading environments to provide significantly improved structural performance as compared to metals. On the other hand, because of the weakness of unidirectional fiber-reinforced composites in the transverse direction, and because loading environments are rarely uniaxial, quasi-isotropic layups are often used to provide sufficient strength and stiffness in all directions. A methodology has been developed to tailor the layup and stacking sequence to local states of stress across a composite structure, which can provide improved strength or reduced weight relative to a quasi-isotropic baseline. This methodology uses geometry and external loads as fixed parameters, and optimizes layup parameters at the level of individual finite elements using advanced genetic algorithms.