A design and manufacturing method for establishing the minimum quantity of carbon fiber for a specific beam deflection and stress is detailed. The design selects the most effective carbon fiber position combined with identical fiber stress throughout the structure. The product examples are a cantilever beam, beam weight only, also a loaded floor beam having three supports. The carbon fibers are entirely longitudinal and are at the extremities of the vertical axes. The quantity of fibers is varied along the beam length to attain a constant stress. Because the fibers are longitudinal they also have a constant strain. The summations of bending moments of all beam structural elements plus loading and factors allow determination of moments of inertia values for each inch or foot space along the length of the beam. The section moduli for each moment of inertia are made proportional to the bending moments at each space location. Constant fiber strain produces deflection of a beam that is a radius of curvature. It is then possible to satisfy the requirements for beam deflection having constant fiber stress and using the minimum amount of carbon fiber. Constant strain beams can be fabricated on filament winding and filament placement machines capable of longitudinal and helical fiber orientations. Steps in fabrication include the use of a foam mandrel that becomes part of the beam structure. The carbon fiber members of the beam are resin vacuum infused, placed on the foam in a staged condition then over wound with low cost fibers. Fabrication time, weight and material costs are significantly less than those of constant section or straight taper beams.
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