Mixed mode fracture in an inclined center crack repaired by composite patching

Abstract The use of bonded composite patches is among favorite reinforcement methods for repairing cracked structures. Although extensive research studies deal with the safety evaluation and life prediction of repaired components, most of these investigations are concentrated on pure mode I loading (or opening mode of crack deformation). Meanwhile in many engineering structures, cracked components are subjected to mixed mode I/II. In this paper the effects of composite patching are investigated on fracture behavior of an inclined center crack, under different combination of modes I and mode II loading conditions. A three-dimensional finite element model of the single-sided repaired specimen is used to study the effect of composite patching on the crack tip parameters ( K I , K II and T -stress). Then the fracture initiation angle and the fracture strength of repaired crack are predicted by using the generalized maximum tangential stress criterion. The effects of composite laminate configuration and adhesive properties on the performance of bonded composite patch are also investigated herein. It is shown that parameters like mode mixing, patch thickness and properties of film adhesive can influence significantly the crack tip parameters and hence the fracture strength of the repaired specimens under mixed mode loading conditions.

[1]  Frank A. McClintock,et al.  Discussion: “On the Crack Extension in Plates Under Plane Loading and Transverse Shear” (Erdogan, F., and Sih, G. C., 1963, ASME J. Basic Eng., 85, pp. 519–525) , 1963 .

[2]  Turaga V.R.S. Umamaheswar,et al.  Modelling of a patch repair to a thin cracked sheet , 1999 .

[3]  Hussain,et al.  Strain Energy Release Rate for a Crack Under Combined Mode I and Mode II , 1974 .

[4]  Rhys Jones,et al.  Finite Element Analysis of Patched Cracks , 1979 .

[5]  F. Erdogan,et al.  On the Crack Extension in Plates Under Plane Loading and Transverse Shear , 1963 .

[6]  F. Hauser,et al.  Deformation and Fracture Mechanics of Engineering Materials , 1976 .

[7]  J. Hancock,et al.  Two-Parameter Characterization of Elastic-Plastic Crack-Tip Fields , 1991 .

[8]  Michael A. Sutton,et al.  Development and application of a crack tip opening displacement-based mixed mode fracture criterion , 2000 .

[9]  Andrzej Seweryn,et al.  A non-local stress and strain energy release rate mixed mode fracture initiation and propagation criteria , 1998 .

[10]  M. Ayatollahi,et al.  Computation of stress intensity factors (KI, KII) and T-stress for cracks reinforced by composite patching , 2007 .

[11]  M. Pavier,et al.  The role of T-stress in brittle fracture for linear elastic materials under mixed-mode loading , 2001 .

[12]  L. Rose.  An application of the inclusion analogy for bonded reinforcements , 1981 .

[13]  M.R.M. Aliha,et al.  Cracked Brazilian disc specimen subjected to mode II deformation , 2005 .

[14]  Majid R. Ayatollahi,et al.  Determination of T-stress from finite element analysis for mode I and mixed mode I/II loading , 1998 .

[15]  M. Ayatollahi,et al.  Mixed mode brittle fracture in PMMA—An experimental study using SCB specimens , 2006 .

[16]  A. Baker.  Repair of cracked or defective metallic aircraft components with advanced fibre composites—an overview of Australian work , 1984 .

[17]  N. Hallbäck,et al.  The Influence of Finite Geometry and Material Properties on Mixed-Mode I/II Fracture of Aluminium , 1997, International Journal of Fracture.

[18]  G. Sih.  Strain-energy-density factor applied to mixed mode crack problems , 1974 .

[19]  J. G. Williams,et al.  Fracture under complex stress — The angled crack problem , 1984 .

[20]  M. Williams,et al.  On the Stress Distribution at the Base of a Stationary Crack , 1956 .

[21]  F. Nilsson,et al.  Mixed-mode I/II fracture behaviour of an aluminium alloy , 1994 .

[22]  Ki-Hyun Chung,et al.  Fracture mechanics analysis on the bonded repair of a skin/stiffener with an inclined central crack , 2002 .

[23]  M. Belhouari,et al.  Computation of the stress intensity factors for repaired cracks with bonded composite patch in mode I and mixed mode , 2002 .

[24]  Andrew H. Sherry,et al.  COMPENDIUM OF T‐STRESS SOLUTIONS FOR TWO AND THREE DIMENSIONAL CRACKED GEOMETRIES , 1995 .

[25]  P. C. Paris,et al.  Stress Analysis of Cracks , 1965 .

[26]  Alan Baker,et al.  Repair of mirage III aircraft using the BFRP crack-patching technique , 1984 .

[27]  Albert S. Kobayashi,et al.  Axial crack propagation and arrest in pressurized fuselage , 1991 .

[28]  A. Baker.  Bonded composite repair of fatigue-cracked primary aircraft structure , 1999 .