| 摘要 |
A sheet material (1) includes a stiffness-increasing concave-convex part (20). A first reference plane (K1) and a second reference plane (K2) serve as a reference system. Numerous at least substantially (H) shaped first reference areas (213), each including two parallel longitudinal bar parts (214) and a latitudinal bar part (215) that connects center portions the two parallel longitudinal bar parts together, are arrayed with the same orientation in the second reference plane (K2). First areas (21) respectively protrude from the first reference areas (213) in the second reference plane (K2) toward the first reference plane (K1). Each first area (21) includes a first top surface (211), which is a reduced projection of its first reference area (213) into the first reference plane (K1), and first side surfaces (212) that connect the outer periphery of the first top surface (211) with the outer periphery of the corresponding first reference area (213).
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