PSI - Issue 60

Amardeepa KCS et al. / Procedia Structural Integrity 60 (2024) 60–74 Amardeepa KCS/ Structural Integrity Procedia 00 (2023) 000–000

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to high stress and failure index value around the stringer cut-out region. In the next level of analytical study, the L angle from the same region is considered for continuing the standalone analytical study marked in the dotted rib region, as shown in Figure 9(a) at stringer number 8. Figure 9(b) shows the FE model of an L angle flange created by dividing the mesh into shell elements using 2D CQUAD4 and CTRIA3 elements, assigned with PCOMP property and defined by MAT8 material card of NASTRAN®, which have six degrees of freedom in displacements and rotations.

Fig. 6. Displacements of the wing box

Fig. 7. Net displacements of the wing box and wing

Fig. 8. High stress and high failure index value around the stringer cut-out region in the rib of wing/wing box

The dimensional details of the L angle considered in the present standalone study are shown in Figure 9(c). The composite material property is defined with the experimentally measured values E11=130 Gpa, E22=10 Gpa, υ=0.35, and G=5 Gpa is assigned to 2D CQUAD4 elements with different ply orientations [+45/-45/0/+45/-45/90] s as defined in the wing and the wing box. The composite laminate is divided into four separate layers as it contains the four orientations of plies, and these layers are offset by 0.45 mm. Each layer contains a nearly equal number of composite layers in sequence, counting from one of the faces of the laminate. One limitation of carrying out a two-dimensional FE analysis is that it cannot give the stress components in the third dimension. In experimentally validated analytical studies carried out by authors [6,7], the third directional stresses were captured by modelling 1D elements across the thickness of the composite laminate. A similar approach is also adopted in this present study to capture the third directional stress components acting normal to the outer/inner surfaces of the composite laminate at all points. Various stress components like shear and normal stresses acting in this area govern the failure of the L angle.

(b) Parts of the L angle with stringer cut-out

(c ) Dimension of the L angle

(a) A typical IS rib

Fig. 9. Detailed features of the Interspar rib