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Journal of Failure Analysis and Prevention

, Volume 15, Issue 6, pp 906–914 | Cite as

Crack Initiation Study on Aircraft Composite Rib with Semi-elliptical Surface Flaw

  • V. Sivakumar
  • G. Bharath Kumar
  • Ambati Gautham
Technical Article---Peer-Reviewed

Abstract

A parametric study on crack initiation was done by having different sizes of cracks at different locations in a rib section of an aircraft using finite element techniques. A semi-elliptical surface flaw in a typical Boeing-747 rib section having circular cut-out and experiencing an in-plane shear loading was considered for the analysis. A laminated composite square plate around a centrally located cut-out was selected in the wing rib for computation purpose. A delamination has been modeled in between the composite layers in the form of a semi-elliptical surface crack using node duplication technique. As there are no theoretical solutions for mixed mode loading problems, the general purpose finite element package ABAQUS was used to obtain the Stress Intensity Factor (SIF) along the crack edge. These stress intensity factor (K C) values were further compared with the fracture toughness of the material to determine the probability of crack initiation. It was observed that the modes of failure change with the dimensions of the crack and also showed a greater tendency towards the crack initiation.

Keywords

Crack initiation Delamination Stress intensity factor Composite Finite element method 

List of Symbols

K

Stress intensity factor

KIc

Critical stress intensity factor for mode 1

KIIc

Critical stress intensity factor for mode 2

KIIIc

Critical stress intensity factor for mode 3

c

Semi-major axis

a

Semi-minor axis

E1, E2, and E3

Principal Young’s moduli in fiber direction and other two transverse directions, respectively

G12, G13, and G23

Shear moduli associated with planes 1–2, 1–3, and 2–3, respectively

µ12, µ13, and µ23

Poisson’s ratio associated with planes 1–2, 1–3, and 2–3, respectively

σz

Normal stress component in out of plane direction

τ13 and τ23

Shear stress components in respective 1–3 and 2–3 planes

n

Normal vector

q

Local direction of virtual crack extension

W

Elastic strain energy

σ

Applied stress

I

Identity matrix

k

Stress intensity factor for auxiliary field

B

Pre-logarithmic energy factor matrix

J

J-integral

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Copyright information

© ASM International 2015

Authors and Affiliations

  • V. Sivakumar
    • 1
  • G. Bharath Kumar
    • 1
  • Ambati Gautham
    • 1
  1. 1.Department of Aerospace EngineeringAmrita Vishwa VidyapeethamCoimbatoreIndia

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