PSI - Issue 60

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

66

7

This numbering system helped post-process the results with proper output data control. The entire surface area of the L angle is divided into various zones to identify the location in web, radius, and flange regions as shown in Figure 11(b). Zone 1 represents the flat laminate in the flange region, Zone 2 is the fillet or radius region, Zone 3 is the web region with regular CQUAD elements, and Zone 4 CQUAD elements aligned radially around the stringer cut-out region. The shear force components of the 1D CBAR elements are aligned in the plane of composite laminate either in the flat or fillet region, while the axial force component is placed normal to the composite laminate surface in all zones, as shown in Figure 11(b). The direction of these force components is symmetrical about its axis of symmetry, as shown in the same Figure. The 1D elements are assigned resin material properties, and 2D elements are assigned CFRP material properties for analytical studies. 4.1. Loads and Boundary Condition The global displacement values are extracted for the set of fasteners connecting the top skin to the IS rib of the wing box FE model, as shown in Figure 9. A maximum displacement value is chosen from the extracted values and applied as enforce displacements D1 and D2 (load) in the standalone FE model of L angle, as shown in Figure 12 where D1 = 0.6 mm and D2 = 0.71 mm are the displacement values extracted at the fasteners located on either side of the stringer cut-out as shown in Figure 13. The boundary conditions are applied as an enforced displacement at an appropriate location, as shown in Figure 14 to simulate the global behavior of the wing box and wing. All the 3 translations' degree of freedom (∆x, ∆y, and ∆z) is constrained using an SPC (single point constraints) load card, and 6 degrees of freedom (∆x, ∆y, ∆z, θx, θy, and θz) are constrained using an SPCD card; 3 translation and 3 rotations are applied on the local model in ordered to solve for the static analysis. The same FE analysis is carried out for different displacement factors to know the safety parameters and overall structural integrity, as shown in Table - 1.

Fig. 14. Boundaries of an L angle from the global wing box

Fig. 13. exploded view of a typical fastener location of L angle with maximum displacement observed

Fig. 12. Loads and boundary conditions applied in the FE model of L angle

Table 1. Displacements of fasteners for the L angle to check failure for different cases

No. Fasteners/ Node No.

1

2

3

4

5

6

7

8

9

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]

6027185/ Displacement 1 (Z-axis)

0.66

1.4

2.1

2.2

2.25

2.3

2.4

2.5

2.6

6027184 / Displacement 2 (Z-axis)

0.71

1.5

2.3

2.4

2.45

2.5

2.6

2.7

2.8

4.2. Challenges Understanding the failure of composite structures even after carrying out mechanical tests becomes cumbersome due to the non-availability of appropriate analytical and numerical methods, modelling approaches, and suitable failure criteria. This work presents the numerical methods and FE modelling approach adopted for understanding the failure load, and the location of failure of an L angle flange of composite IS rib that experiences out-of-plane loading due to