Advanced Laminated Composite Applications for Doubly-Curved Shell Structural Components with Variable Curvature

Theoretical modeling of laminated composite shells is a wide-ranging topic that falls out into different engineering branches. Shell structural components can be found in civil, mechanical, naval and aerospace engineering as roofs, hoods, hulls, wings and cockpits, respectively. The studies over doubly-curved shells have been growing, because the use of advanced and ground-breaking materials have hitherto been increasing. These studies have a direct and immediate application due to the great advantages in terms of weight loss and enhanced strength that these new materials have, when compared to classic applications. However classic theoretical modeling cannot be considered when laminated composite structures are analyzed. Because the high anisotropic behavior of these structures is not predicted accurately using the well-known thin shells theories. Most of the times, higher-order equivalent single layer and layer-wise approaches have to be introduced to accurately capture the mechanical behavior of these components and to avoid the computational inefficiency of the 3D elasticity. Due to their complexity laminated composite shells can be hardly studied using exact and semi-analytical solutions, since only a few configurations can be solved. Generally speaking the finite element method is the most wide-spread tool for the numerical computation of these structures. Commercial finite element implementations approximate the geometry of a generic component using flat plates that only get close to the physical shape. For this reason the present implementation employs a differential geometry description for the numerical design of doubly-curved structures when variable radii of curvatures are present. Since the geometric parameters change point by point an advanced collocation method is carried out. The present procedure results to be stable, accurate and reliable with respect to other numerical approaches. Both the free vibration and the static problems will be discussed with a particular emphasis on the stress and strain recovery procedure, which is a major problem for the evaluation of through-the-thickness quantities of laminated composite shell structures.