Gettou is a natural plant that grows wild in sub-tropical regions such as Okinawa, and it has anti-mold characteristics. In this paper, the flexural modulus of Fiber Reinforced Plastics (FRP) using gettou fiber fabricated by injection molding was predicted from homogenization method using Finite Element Method (FEM). Homogenization method is a multi-scale analysis method that can be possible to predict the elastic modulus of composite material. In order to compute homogenization method using FEM, micro structure model of unit cell was generated from observation result of cross section of FRP using gettou fiber by optical microscope. Next, cross section of gettou fiber was observed by Scanning Electron Microscope (SEM) in order to consider occurrence of compression of internal pores of gettou fiber in FRP by injection molding process. From observation result of SEM, the internal pore ratio of gettou fiber was 35%. This result suggests that elastic modulus of gettou fiber in FRP increased in comparison to the obtained value from gettou single fiber tensile test. By observation result of cross section of FRP using optical microscope, in addition, gettou fiber orientation in FRP displayed incline in comparison to injection direction with increasing content of gettou fiber. Thus, effect of gettou fiber orientation was considered to be elastic modulus of gettou fiber and finite element division of unit cell. From comparison of experimental result and predictions of homogenization method and Halpin-Tsai equation, both prediction methods showed good agreement with experimental results under 14 vol.% content of gettou fiber. Especially, the results of Halpin-Tsai equation showed tendency to be on the upper limit side of experimental results. On the other hand, results of homogenization method tended to be on the lower limit side of experimental results. Therefore, it is confirmed that experimental result can be predicted using both Halpin-Tsai equation and homogenization method.

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Water molecules have a characteristic absorption band in the infrared region from 2.78 to 3.13 μm due to OH vibration. Therefore, Er:YAG laser, which has oscillation wavelength of 2.94μm, is efficiently absorbed by water molecules and is finally converted into thermal energy. In this study, a new type of laser transmission welding for amorphous polymer that uses the radiation absorption coefficient change by moisture adsorption was proposed. Both experimental and numerical simulation studies were carried out to investigate the feasibility and to discuss the characteristics of the proposing method. Through the transmittance measurement in infrared region by FT-IR, polycarbonate was chosen as the test material. By comparing the calculated temperature distribution with the size of welded area, the effect of moisture adsorption on the state of welding was discussed. Tensile test of the welded sample in shear mode was also performed to investigate the weld strength. Fracture strength of the welded plates of 0.5mm thickness was increased about 50%, because the provided radiation energy was efficiently absorbed at the welding interface. In conclusion, it was fundamentally confirmed that the proposed technique is useful for improving the efficiency of laser transmission welding.

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『成形加工』 第 26 巻 6 号掲載の論文 「射出成形におけるスクリュ形状の違いによる FRTP の繊維長と分散性」 Fig．8 (281 ページ右段) におきまして，(e) 図の欠落がございました．関係各位にご迷惑をおかけしましたことをお詫び申し上げます．正しくは次の通りです．

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