Progressive damage modelling of bonded composite repairs P. Papanikos a, * , K.I. Tserpes a , G. Labeas b , Sp. Pantelakis b a ISTRAM, Patron-Athinon 57, Patras 26441, Greece b Laboratory of Technology & Strength of Materials, Department of Mechanical Engineering & Aeronautics, University of Patras, Patras 26500, Greece Available online 2 February 2005 Abstract Presented is a three-dimensional progressive damage model that can assess the mechanical behaviour of bonded composite repairs of cracked metallic plates. The model is able to assess the stress intensity factor (SIF) at the crack tip, patch debonding and damage accumulation in the composite patch as functions of the applied load. Considered are the stress analysis, failure analysis and material property degradation. Stress analysis is performed using a three- dimensional detailed parametric finite element (FE) model developed using the ANSYS FE code. Failure analysis is performed using a set of stress-based polynomial failure criteria. Material property degradation of the failed material (patch and adhesive) is performed using appropriate degradation rules. The three model components have been pro- grammed in the ANSYS FE code creating a user-friendly parametric macro-routine, which can be easily applied to bonded repairs of different materials and configuration. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Progressive damage; Bonded repair; Composite; Finite element; Air frame 1. Introduction Damage during the service life is a natural char- acteristic of any airframe. Performing repairs to damaged airframe components is virtually inevita- ble, primarily for economic reasons. A badly implemented repair can be more dangerous than the unrepaired configuration. Out of the various types of damages, cracks can possibly be repaired by either mechanically fastened doublers or bonded patches. The bonded patch offers many advantages over the mechanically fastened dou- bler, which include improved fatigue life, reduced corrosion, in situ applications and easy confor- mance to complex aerodynamic contours. Bonded composite repairs have been shown to provide high levels of bond durability under operating con- ditions. Researchers in Australia have extensively 0167-8442/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.tafmec.2005.01.004 * Corresponding author. Tel.: +302610426570; fax: +302610428924. E-mail address: p.papanikos@istram.gr (P. Papanikos). Theoretical and Applied Fracture Mechanics 43 (2005) 189–198 www.elsevier.com/locate/tafmec