Issue 16

F. Carta et alii, Frattura ed Integrità Strutturale, 16 (2011) 34-42; DOI: 10.3221/IGF-ESIS.16.04 38 M ATERIAL PROPERTIES The following elastic constants were used in the FE analysis. Skin and doublers: E = 73100 MPa Young’s modulus ν = 0,33 Poisson’s ratio . Stringers: E = 71700 MPa Young’s modulus ν = 0,33 Poisson’s ratio . L OADS AND CONSTRAINTS n Fig. 8, the loads and the constraints are shown, while the bonding between the components of the panel was reproduced in Abaqus with the TIE constraint. In the simulation analysis the maximum load of the experimental tests was considered ( F max = 280 kN ). Figure 8 : Loads and constraints on the quarter of the panel M ODELING AND MESH n the study, two typologies of element ( shell and solid ) and different refinements of the mesh at the crack tip were considered (see Fig. 9), namely: - a 3D model with shell elements; - a 3D model with solid elements (linear or quadratic geometric order) - a 3D model with discretization by means of shell-to-solid coupling. (a) (b) (c) (d) Figure 9 : Different modeling typologies: second-order shell elements with collapsed Quarter-Point Node elements at the crack tip (a) , first-order solid elements collapsed at the crack tip (b) , second-order solid elements with collapsed Quarter-Point Node elements at the crack tip (c) , same as (a) - (c) with shell-to solid coupling between solid and shell parts (d) . I I