A numerical procedure for the simulation of skin–stringer debonding growth in stiffened composite panels

In this paper, a numerical study on the skin-stringer debonding growth in composite panels under compressive load is presented. A novel numerical procedure, for the selection of proper material parameters governing the traction-separation law in Cohesive Zone Model (CZM) based elements, is introduced and demonstrated. Indeed, the proposed procedure uses Virtual Crack Closure Technique (VCCT) based FEM analyses on Double Cantilever Beam (DCB) and End Notched Flexure (ENF) specimen to characterize the traction-separation law, respectively, for fracture mode I and mode II. The established traction-separation laws are then applied to composite structures containing inter-laminar damages modeled by cohesive elements. To validate the proposed approach, a single stringer panel under compression with an artificial debonding between skin and stringer, has been considered. The numerical results, in terms of displacements and debonding size as a function of applied compressive load, have been compared to experimental data available in literature providing a good numerical-experimental correlation.