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Analysis of the Failure of Bonded Interface between Aluminium Skin and FRP Patch Using Cohesive Zone Model

  • Amol RasaneEmail author
  • Prashant Kumar
  • Mohan Khond
Original Contribution
  • 65 Downloads

Abstract

A single-sided patch of unidirectional carbon fibre-reinforced polymer composite was bonded on a 1.0 mm-thick skin of aluminium alloy 6061-T6 with a centre crack of 25 mm length. Two kinds of patches were studied: (1) 1-ply patch and (2) 2-ply patch. Experiments were conducted to determine the strength of 1-ply patch. It was then simulated using finite element analysis employing a cohesive zone model in ANSYS 15.0. When the repaired specimen was subjected to a quasistatic load, the patch started separating at the crack edge due to the combined action of high peel and the shear stresses at the interface. The rate of separation was slow initially, but grew rapidly at high loads. Separation cracks were also initiated at the leading edges at high loads, leading to catastrophic failure of the specimen. The numerically obtained failure load was compared with that obtained through the experiments, and the effectiveness of using the cohesive zone model for simulating the interface failure was established. The numerical analysis was then applied to predict the failure behaviour of 2-ply patches. The strengths of the 1-ply patch and 2-ply patch for different patch lengths were compared. The strength of 2-ply patch was found to be considerably higher over that of 1-ply patch for short-length patches. However, the difference diminished with the increasing patch length.

Keywords

Finite element analysis Cohesive zone model Patch separation Repair of cracks Aluminium alloy 

List of symbols

E1

Longitudinal modulus

E2

Transverse in-plane modulus

E3

Transverse in-plane modulus

Fmax

Maximum induced load in skin

G12

In-plane shear modulus

G13

Out-of-plane shear modulus

G23

Out-of-plane shear modulus

GI

Fracture energy in mode-I

GIc

Critical fracture energy in mode-I

GII

Fracture energy in mode-II

GIIc

Critical fracture energy in mode-II

L

Length of patch

Mb

Induced bending moment

Tn

Normal traction component

Tnmax

Maximum normal traction

Tt

Shear traction component

Ttmax

Maximum shear traction

u2

Displacement of free end of specimen

v12

Major in-plane Poisson’s ratio

v13

Major out-of-plane Poisson’s ratio

v23

Major out-of-plane Poisson’s ratio

W

Width of patch

δn

Normal displacement component

δnc

Critical normal displacement

δt

Tangential displacement component

δtc

Critical tangential displacement

σ33

Peel stress

σ

Far-field induced stress

τ13

Shear stress at the interface

Notes

Acknowledgements

The authors are thankful to the Structures Panel of Aeronautics Research and Development Board (ARDB), Defence Research and Development Organization (DRDO), New Delhi, India for providing support for this study.

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Copyright information

© The Institution of Engineers (India) 2018

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringCollege of EngineeringShivajinagar, PuneIndia

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