The purpose of this study is to suggest estimated formula of stress concentration factor on weld toe of non-load-carrying cruciform welded joints by externally bonded CF sheets. The regression lines of the relationship between numbers of CF sheet layers and stress reduction factor was analytically investigated using finite element (FE) model varying the toe radius. Further, estimated formula of stress concentration factor has been proposed by combined with the estimated formula of the stress concentration coefficient at the weld toe. The verification of the proposed estimated formula was carried out by comparing the stress concentration factor by tensile test and FE model simulating the weld toe of specimen.
