Optimized Design of Pultruded Composite Beams

Abstract

An optimization method, based on classical lamination theory and a numerical search, for the minimum cost design of a glass fiber reinforced composite box beam is discussed. A sequential unconstrained minimization technique is utilized to find the lowest cost box beam which satisfies particular geometric, loading, and failure criteria. In formulating the optimization problem, the deflection and stresses of a box beam during loading must be predicted. A composite box beam model is presented which provides bending stiffness, midpoint deflection, and load at failure for the beam. The box beam model is validated by comparing model predictions with experimental data for a commercially available (proprietary) box beam design. An optimization code is developed, incorporating this box beam model, which yields a new box beam design with a 6 percent reduction in raw material cost as compared to the current commercial beam design. Similar beam bending models for circular and elliptical hollow cross sections are presented. A methodology to optimize these cross sections is discussed.