PSI - Issue 60

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Procedia Structural Integrity 60 (2024) 60–74

Third International Conferences on Structural Integrity 2023 (ICONS 2023) Analytical Assessment of Composite L Angle Strength Under

Internal Fuel Pressure in Composite Wing Amardeepa KCS 1a* , Polagangu James 2b , Byji Varughese 3c 1 Principal Scientist, 2 Senior Principal Scientist, 3 Chief Scientist Advance Composites Division, CSIR, National Aerospace Laboratories, Bangalore, India .

Abstract The Interspar (IS) box stores the turbine fuel in the composite wing of an Aircraft. The filled fuel is under pressure that induces out-of-plane stresses on all the wing's structural members around the fuel tank's boundary. The wing is designed using carbon fiber reinforced plastic (CFRP) with the co-curing of the bottom skin and its stringers along with front and rear spars. A suitable number of cut-outs are made on the top and bottom sides of the IS ribs for the stringer to pass through them. The global finite element analysis showed that the stringer cut-out regions in the IS ribs are highly stressed, as they are subjected to out-of-plane load due to internal fuel pressure, which induces transverse tensile stress in the cut-out region. Resin is the weakest material in the composite laminate, but it has to resist the high stress component due to out-of-plane loads. The top and bottom flanges of the 'C' section IS ribs geometrically form an L angle section with a stringer cut-out made in it. At the L angle location, the IS ribs are critical from both the strength and stiffness point of view. Strength and stiffness at the interface of the fastener joint are essential factors in maintaining the composite wing's overall structural integrity under internal fuel pressure. The authors adopted the same standalone finite element (FE) modelling approach developed for the Bond Energy Method and carried out appropriate analytical studies to ascertain the safety and structural integrity of the composite wing under internal fuel pressure. This article presents the analytical study carried out on the standalone FE model of an L angle with the stringer cut-out introduced at its appropriate position. The static stress analysis is carried out by enforcing the global displacement on this standalone FE model and extracting three force components in CBAR beam elements representing the resin property in the transverse direction of the composite laminate. The stresses are calculated outside the analysis deck using Excel® spreadsheets. The maximum Normal Stress (σ n ) in the L angle flange is found to be 13.25 MPa, which is well within the resin or transverse tensile strength of the composite laminate 53 MPa, a nd the shear stress is found to be 11.10 MPa, which is less than the resin shear strength property of 23 MPa. Hence the study

* Corresponding author. fax: 91 80 25267352 E-mail address: amardeepa@nal.res.in

2452-3216© 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the ICONS 2023 Organizers

2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the ICONS 2023 Organizers 10.1016/j.prostr.2024.05.031