Skin-Stiffener Separation in T-Stiffened Composite Specimens in Postbuckling Condition

An experimental and numerical investigation was conducted to study the skin-stiffener separation of single T-shape stiffener specimens in postbuckling condition. Three specimens were manufactured with a centrally located Teflon insert, and were loaded in compression until collapse. Deformation patterns and separation evolution were monitored during the tests. To measure the full-field displacements and the strain distributions of the specimens, a digital image correlation (DIC) system was used. Skin-stiffener separation was observed and measured with an ultrasound system. Finite-element (FE) analyses were conducted to capture interlaminar damage mechanism based on the virtual crack closure technique. The numerical analysis accurately predicted the postbuckling deformation and the skin-stiffener separation behavior. The close correlation between the experimental and numerical results allows for further exploitation of the strength reserve in the postbuckling region and wider design options for the next generation of composite aircraft designs.