PSI - Issue 60

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

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FAR 23 standards. In addition, critical fuel pressure distribution and other inertia loads are considered for analysing the wing structure. Figure 3 shows the global wing analysis results with the distribution of Yamada Sun's failure index value for the internal fuel pressure of 12.5 PSI. The results show that an L angle region in IS ribs # 7,8,9 and 10 is subjected to high stress and failure index value around the stringer cut-out region. The wing design cannot be cleared with this high failure index (safe limiting value is <1.00) unless it is proven separately that this L angle region in IS ribs is experimentally or analytically safe. Before taking up experimental studies, demonstrating its safety through analysis is necessary as per certification requirements and regulations. Therefore, the present analytical study considered a section from the global wing model extended between stations #6 to 10 that represents the full global wing features in the wing box structure, as shown in Figure 4. The dimensional details of the wing box measure 1150 mm in length, 1148 mm in width at the root, and 950 mm in width at the tip. The depth is 340 mm at the root and 290 mm at the tip. This composite wing box is part of a global composite wing FE model considered for this study purpose. The study simplifies the bigger size problem into a smaller one by considering the typical region of the wing box encircled within the dotted line shown in Figure 1(a) and (b). The pre-and post-processing of the finite element model of the wing box is carried out using HyperMesh® V19 with MSC Nastran interface features, and various analysis solutions are obtained through MSC/NASATRAN® R2016 Solver. Figure 5(a)&(b) shows the load and boundary condition applied in the wing box to simulate balloon constraints [9,10], allowing the skins and spars to expand freely under applied internal fuel pressure without offering any nature of physical constraints seen in a blown balloon or football.

Fig. 3. High-stress regions at the rib location of the global wing model

Fig. 4. FE model of the wing box Station (6-10)

(b)

(a)

Fig. 5. Loads and Boundary conditions of the wing box

Figure 6 shows the deformed shape of the wing box when subjected to internal fuel pressure with balloon constraints. Figure 7 shows the net displacement comparison of the wing and wing box, which is found within a 4-5 % difference at the maximum displacement region. The failure index value distribution or high stress region in the L angle of typical IS ribs of the standalone wing box is shown in Figure 8. It also shows the same high stresses at the stringer cut-out region in the rib of the wing box, similar to that of the global wing. Therefore, it is found that the L angle flange of IS ribs is the most critical in the fuel tank region. Hence the standalone FE analysis is carried out on the L angle to assess and ensure the strength and safety of the composite wing structure for maintaining the overall structural integrity.

4. FINITE ELEMENT ANALYSIS OF STANDALONE L ANGLE Figure 3 and Figure 8 show the global wing and wing box analysis that an L angle region in rib # 7,8,9,10 is subjected