Post-Buckling Experimental Tests and Numerical Analyses on Composite Stiffened Panels

Numerical analyses and experimental tests until collapse are performed on stiffened composite flat panels designed to work in the post-buckling field. Indeed, four different finite element analyses are performed: eigenvalue, nonlinear static with modified Riks' method and dynamic analyses both using an implicit and an explicit solver algorithm. Data obtained by the four different analyses are compared giving closed results in terms of equilibrium path and of deformed shape evolutions. Experimental tests are then performed considering two nominally equal stiffened flat panels. During the axial compression tests the out-of-plane deformations are carried out by using Moirè's fringes method. Experimental results show how structural collapse take place suddenly and due to failure of the stiffener blades. Numerical analyses and experimental tests are finally compared. Data are in good agreement and finite element analyses seem able to predict with enough accuracy the post-buckling behavior also pointing out the more critical areas in terms of failure probability. Obtained results are particularly relevant also because the panel configuration was designed by using a fast optimization procedure and therefore the tested panels represent high efficient structures.