Optimizing the size of a CFRP patch to repair a crack in a thin sheet

Abstract

ABSTRACTOne of the several techniques to repair cracks in structural sheets consist in bonding polymer composite patches. The effectiveness of the repair for restoring the quasistatic strength of the structure depends largely on the adhesively bonded interface. The interface fails due to interfacial separation caused by the high peeling and shearing stresses. The geometrical dimensions, that is, patch length and width, have significant effect on the interface separation and they need to be optimized. The failure strength of the patch was determined by a numerical analysis using the cohesive zone model. Twenty-five numerical analyses were carried out as per the L-25 Taguchi orthogonal array followed by ANOVA which indicated the greater contribution of the patch width toward the failure of the patch. The failure stresses thus obtained were used to generate a response surface in ANSYS Design Explorer Module. A design criterion in terms of the percentage increase of the failure stress over the yield stress of the skin was used for minimizing the area of the patch. The optimum length and width of the patch corresponding to the minimum patch area were obtained by plotting the response curves generated from the response surface.