Experiment and design methods of composite scarf repair for primary-load bearing structures

A relative thick plate of composite being repaired by scarf bonding was substituted as the scarf joints and studied under tensile load in this paper. The experimental investigation told us the ultimate capability of load and failure mechanism of composite scarf joints. In order to explain failure mechanism for scarf bonding repair of composite structures distinctly, FEM based on continuum damage mechanics (CDM) was carried out. CDM equations were derived by adding the delamination mode and 3D Hashin criteria based on strain into the composite constitutive relation. Furthermore, a modified semi-analytical method (MAM) was developed to obtain shear stress distribution in theory. MAM can improve the accuracy of Harman and Wang method, solve the stress asymmetry, obtain secondary peak of shear stress, and increase the highest peak of stress. In the end, the discussions for the methodologies of MAM, CDM and linear FEM were executed to compare the errors of predicting ultimate load. The discussion revealed that MAM has sufficient accuracy as an analytical methodology which could be utilized to design composite scarf repairs in a short cycle simply.