In various embodiments, the outer metal part 1110b manufactured according to FIG. 11B may form the frame structure of the side member 200 illustrated in FIGS. 6A and 6B. For example, when the opening 250 is formed in the relatively thick portion 1113, the inner surface of the opening 250 may be formed by only a first metal part (e.g., the first metal part 210 of FIG. 6A) as illustrated in FIGS. 6A and 6B.
Referring to FIG. 11C, an inner metal part 1120 having a plate shape may be coupled to an outer metal part 1110 having a frame shape. The inner metal part 1120 may include one or more bridges 1122 connected to the outer metal part 1110. As described above, bumpy structures may be formed on contact surfaces of the outer metal part 1110 and the inner metal part 1120 through laser machining. In various embodiments, the inner metal part 1120 may be formed through a die casting process.
