Strength prediction of adhesively-bonded scarf repairs in composite structures under bending

Abstract

This work reports on the experimental and numerical study of the bending behaviour oftwo-dimensional adhesively-bonded scarf repairs of carbon-epoxy laminates, bonded with theductile adhesive Araldite 2015®. Scarf angles varying from 2 to 45º were tested. The experimentalwork performed was used to validate a numerical Finite Element analysis using ABAQUS® and amethodology developed by the authors to predict the strength of bonded assemblies. Thismethodology consists on replacing the adhesive layer by cohesive elements, including mixed-modecriteria to deal with the mixed-mode behaviour usually observed in structures. Trapezoidal laws inpure modes I and II were used to account for the ductility of the adhesive used. The cohesive lawsin pure modes I and II were determined with Double Cantilever Beam and End-Notched Flexuretests, respectively, using an inverse method. Since in the experiments interlaminar and transverseintralaminar failures of the carbon-epoxy components also occurred in some regions, cohesive lawsto simulate these failure modes were also obtained experimentally with a similar procedure. A goodcorrelation with the experiments was found on the elastic stiffness, maximum load and failure modeof the repairs, showing that this methodology simulates accurately the mechanical behaviour ofbonded assemblies.