Delamination Propagation Study on Aircraft Composite Rib Subjected to Fatigue Loading
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TECHNICAL ARTICLE—PEER-REVIEWED
Delamination Propagation Study on Aircraft Composite Rib Subjected to Fatigue Loading V. Sivakumar . P. Gautham Barathwaj . M. Santosh Kumar . D. Srikar
Submitted: 15 June 2020 ASM International 2020
Abstract A computational fatigue study of the propagation of delamination in a composite wing rib has been conducted. A typical Boeing 747 rib having a circular hole with a semi-elliptical delamination was taken as the rib of interest; gust loads experienced during the cruise phase of flight were identified as the source of fatigue. A square section surrounding the circular hole comprising of laminated carbon–epoxy prepreg was isolated from the rib for computational analysis. The lack of analytical solutions for such a problem encouraged the use of the general-purpose finite element software ABAQUS. The delamination mechanism was simulated using the energy-based virtual crack closure technique in tandem with the Paris–Erdogan equation. The delamination propagation with respect to aircraft flight hours was obtained for the aircraft rib, with Mode III tearing dominating the delamination process. A parametric analysis was further conducted for various ply orientations where delamination modes were compared via a frame-based analysis. Significant differences in delamination propagation were observed, and better performing orientations for the given conditions were identified. Keywords Delamination Crack propagation Fatigue analysis Virtual crack closure technique (VCCT) Paris–Erdogan equation Composite Aircraft List of Symbols a Crack length A Crack Area
b C D E 1, E2, E3
f F1 F2 F3 G12 G13 G23 G GI, GII, GIII GIC, GIIC, GIIIC Gequiv GequivC m N u1 u2
V. Sivakumar (&) P. Gautham Barathwaj M. Santosh Kumar D. Srikar Department of Aerospace Engineering, Amrita School of Engineering, Amrita Vishwa Vidyapeetham, Coimbatore, India e-mail: [email protected]
u3 U
Width of delamination Material coefficient of Paris–Erdogan equation Depth of delamination Young’s modulus associated with axial direction and other transverse directions, respectively Fracture criterion Nodal force acting along first principal direction Nodal force acting along second principal direction Nodal force acting along third principal direction Shear modulus associated with 1–2 planes Shear modulus associated with 1–3 planes Shear modulus associated with 2–3 planes Energy release rate Energy release rates associated with Mode I, Mode II and Mode III, respectively Critical energy release rates associated with Mode I, Mode II and Mode III, respectively Equivalent energy release rate Equivalent critical energy release rate Material power term of Paris–Erdogan equation Number of fatigue cycles Nodal displacement associated with the first principal direction Nodal displacement associated with the second principal direction Nodal displacement associated with the third principal direction Strain energy
123
J Fail. Anal. and Preven.
Wext g P m
Work due to external forces Exponent term of BK law P
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