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


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.


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

List of symbols


Longitudinal modulus


Transverse in-plane modulus


Transverse in-plane modulus


Maximum induced load in skin


In-plane shear modulus


Out-of-plane shear modulus


Out-of-plane shear modulus


Fracture energy in mode-I


Critical fracture energy in mode-I


Fracture energy in mode-II


Critical fracture energy in mode-II


Length of patch


Induced bending moment


Normal traction component


Maximum normal traction


Shear traction component


Maximum shear traction


Displacement of free end of specimen


Major in-plane Poisson’s ratio


Major out-of-plane Poisson’s ratio


Major out-of-plane Poisson’s ratio


Width of patch


Normal displacement component


Critical normal displacement


Tangential displacement component


Critical tangential displacement


Peel stress


Far-field induced stress


Shear stress at the interface



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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