| 摘要 |
PROBLEM TO BE SOLVED: To ensure the sufficient strength of a structure as a stiffening material and improve its rigidity as a resin molded body by making a piercing hole with a desired diameter in the inner part of a stiffening material, and also making the shortest distance along the stiffening material surface between the piercing holes to predetermined times as long as the diameter. SOLUTION: Stiffening material 3 is buried over the entire length in the longitudinal direction in the inner part of a resin molded item 1, and formed with a rectangular material. On a central part of each face of the stiffening material 3 in the width direction, a plurality of piercing holes 4 are formed at a predetermined pitch in the longitudinal direction. An inside resin layer 2a and outer peripheral surface resin layer 2b of the stiffening material 3 are connected by a resin pillar 2c for forming an integral resin molded item. The diameter D of each piercing hole 3a is determined to be 10-20mm, and the shortest distance between the piercing holes 4, 4 being adjacent in the longitudinal direction along the surface of the stiffening material 3 is set to be 6-20 times as long as the diameter of the piercing hole 4. |
