Today, more than 50 weight percent of the structure of advanced civil aircraft such as the B787 and the A350 are made up of composite materials. Even large parts such as these planes’ wing spars and fuselage are composites, and in the case of any damage, their replacement is not easily and economically possible. Therefore, their repair is a must. However, a strong methodology for the optimum repair design is necessary to meet the standards and the existing criteria for the designed repairs. For that purpose, we proposed and implemented the axiomatic design methodology to the design of scarf repair, the preferred type of repairing composite structures. Here, the problem is a damaged composite laminate with a through-thickness crack under one-directional and two-directional static tensile loadings. Its scarf repair solutions are designed using the Axiomatic Design approach, a system design methodology that uses matrix methods to systematically analyze the transformation of customers’ needs into functional requirements, design parameters, and process variables. The primary analysis of scarf repair assumed a two-dimensional scarf joint; however, here, both two- and three-dimensional (2D) geometries of the scarf repair are considered. Wang previously showed that the elliptical shape is optimal for the scarf repair, the results of which are used in this paper. Also, the thickness of the glue is neglected, and for calculating the scarf angle, the scarf repair is modeled by a 2D scarf joint as a conservative assumption. As a result of applying axiomatic design to scarf repair design, a formula was obtained, which facilitates the calculation of the doubler overlap length in doubler-scarf repair. Also, a linear algorithm without trial and error was proposed for a scarf repair design that meets all functional requirements of airlines independently.
Oqaz et al. (Sun,) studied this question.