Design and manufacture of hybrid aluminum/composite co-cured tubes with viscoelastic interface layer

The development of hybrid FRP-metal axisymmetric components is a matter of increasing interest in the automotive and aerospace industry for a lightweight design. The hybridization of the technology enables a cost reduction of components production and an increase of mechanical performances together with the ability of machining the surface of the metal tube; this technique guarantees a production improvement since the coating of the tube is no longer required and the pieces can be manufactured in one-step curing cycle. The improvement in bending and torsional stiffness, corrosion resistance and mass reduction of hybrid tubes, in comparison to the single material-built component, has been already demonstrated. A great challenge is to find a way to make hybrid tubes with external metal, avoiding delaminations and detachments that could occur during and after the curing process, due to the different coefficients of thermal expansion between FRP and metal along the axial direction of the tube. For this reason, a component manufacturing process has been studied by experimental and numerical analysis (FEM), including custom process machines and inserting a viscoelastic layer as an interface between the two tubes. Genetic algorithm method has been used to optimize the stacking sequence of a hybrid co-cured metal/composite tube to maximize the flexural stiffness, while applying a strength constraint condition.