Traction–separation laws for progressive failure of bonded scarf repair of composite panel

Repair of composites has become of considerable importance recently as modern commercial airliners employ much more composites in their airframes then previously. Major maintenance, repair, and overhaul (MRO) centers must contend with issues of damage tolerance, efficiency, integrity and cost of repairs. Computational methods have been developed to sufficiently sophisticated levels to aid in the design, evaluation and optimization of proposed repair schemes before they are implemented, potentially saving time and cost. In this paper, parametric studies on progressive failure analysis of a bonded scarf repair of a composite panel was performed. The study finds that finite element models with an appropriate material property degradation scheme using the micromechanics of failure criterion are able to predict the failure load of undamaged and damaged specimen. Results of the parametric studies on adhesive properties suggest that the failure stress of a repaired composite panel is more sensitive to the strength of the cohesive elements than to its toughness when a linear or trapezoidal softening traction–separation law is used, but the influence of adhesive strength is not significant when exponential softening traction–separation law is used.